View source for Tire

{{Short description|Ring-shaped covering that fits around a wheel's rim}}
{{Other uses}}
{{Redirect|Rubber tires|the film|Rubber Tires}}
{{Use American English|date=July 2020}}
{{Use dmy dates|date=July 2020}}
[[File:Large tyre.jpg|thumb|Tire on a truck]]
[[File:Assorted stacked automotive tires.jpg|thumb|Assorted new automotive road tires, showing a variety of tread patterns.]]
[[File:A stack of tractor tyres - geograph.org.uk - 1409842.jpg|thumb|Tractor tires have substantial ribs and voids for traction in soft terrain.]]

A '''tire''' ([[North American English]]) or '''tyre''' ([[Commonwealth English]]) is a ring-shaped component that surrounds a [[Rim (wheel)|wheel's rim]] to transfer a vehicle's load from the [[axle]] through the wheel to the ground and to provide [[Traction (engineering)|traction]] on the surface over which the wheel travels. Most tires, such as those for automobiles and bicycles, are [[pneumatic]]ally inflated structures, providing a flexible cushion that absorbs shock as the tire rolls over rough features on the surface. Tires provide a footprint, called a [[contact patch]], designed to match the vehicle's weight and the bearing on the surface that it rolls over by exerting a pressure that will avoid deforming the surface.

The materials of modern '''pneumatic tires''' are [[synthetic rubber]],<ref>{{Cite web |last=PubChem |title=1,3-Butadiene |url=https://pubchem.ncbi.nlm.nih.gov/compound/7845 |access-date=2024-05-08 |website=pubchem.ncbi.nlm.nih.gov |language=en}}</ref> [[natural rubber]], fabric, and wire, along with [[carbon black]] and other chemical compounds. They consist of a [[tire tread|tread]] and a body. The tread provides [[Traction (engineering)|traction]] while the body provides containment for a quantity of [[compressed air]]. Before [[rubber]] was developed, tires were metal bands fitted around wooden wheels to hold the wheel together under load and to prevent wear and tear. Early rubber tires were solid (not pneumatic). Pneumatic tires are used on many vehicles, including [[car]]s, [[bicycle]]s, [[motorcycle]]s, [[bus]]es, [[truck]]s, [[Heavy equipment (construction)|heavy equipment]], and [[aircraft]]. Metal tires are used on [[locomotive]]s and [[railcar]]s, and solid rubber (or other polymers) tires are also used in various non-automotive applications, such as [[caster]]s, [[cart]]s, [[lawn mower|lawnmower]]s, and [[wheelbarrow]]s.

Unmaintained tires can lead to severe hazards for vehicles and people, ranging from [[flat tire]]s making the vehicle inoperable to [[Blowout (tire)|blowouts]], where tires explode during operation and possibly damage vehicles and injure people. The manufacture of tires is often highly regulated for this reason. Because of the widespread use of tires for motor vehicles, tire waste is a substantial portion of global waste. There is a need for [[tire recycling]] through mechanical recycling and reuse, such as for [[crumb rubber]] and other [[tire-derived aggregate]], and [[pyrolysis]] for chemical reuse, such as for [[tire-derived fuel]]. If not recycled properly or [[Tire fire|burned]], waste tires release toxic chemicals into the environment. Moreover, the regular use of tires produces [[Microplastics|micro-plastic particles]] that contain these chemicals that both enter the environment and affect human health.<ref name="Tan-2023">{{cite journal |journal=Imperial Zero Pollution |last1=Tan |first1=Z. |last2=Berry |first2=A. |last3=Charalambides |first3=M. |last4=Mijic |first4=A. |last5=Pearse |first5=W. |last6=Porter |first6=A. |last7=Ryan |first7=M. |last8=Shorten |first8=R. |last9=Stettler |first9=M. |last10=Tetley |first10=T. |last11=Wright |first11=S. |last12=Masen |first12=M. |date=2023-02-10 |title=Tyre wear particles are toxic for us and the environment |url= http://spiral.imperial.ac.uk/handle/10044/1/101707 |language=en-US-GB |doi=10.25561/101707|hdl=10044/1/101707 }}</ref>

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==Etymology and spelling==
The word ''tire'' is a short form of ''attire'', from the idea that a wheel with a tire is a dressed wheel.<ref>{{OEtymD|tire|access-date=2024-01-18}}</ref><ref name="oed"/>

''Tyre'' is the oldest spelling,<ref>{{OEtymD|tyre|access-date=2024-04-28}}</ref> and both ''tyre'' and ''tire'' were used during the 15th and 16th centuries. During the 17th and 18th centuries, ''tire'' became more common in print. The spelling ''tyre'' did not reappear until the 1840s when the English began shrink-fitting railway car wheels with malleable iron. Nevertheless, many publishers continued using ''tire''. ''[[The Times]]'' newspaper in London was still using ''tire'' as late as 1905.<ref>{{cite book |title=The Cambridge Guide to English Usage |last=Peters |first=Pam |year=2004 |publisher=Cambridge University Press |isbn=978-0-521-62181-6 |page=[https://archive.org/details/cambridgeguideto00pete_0/page/553 553] | url= https://archive.org/details/cambridgeguideto00pete_0/page/553 }}</ref> The spelling ''tyre'' began to be commonly used in the 19th century for pneumatic tires in the UK. The [[Encyclopædia Britannica Eleventh Edition|1911 edition of the ''Encyclopædia Britannica'']] states that ''"The spelling 'tyre' is not now accepted by the best English authorities, and is unrecognized in the US"'',<ref name="eb">{{cite EB1911|wstitle=Tire |volume=26 | pages=1006&ndash;1009; see page 1007 |quote=...The spelling " tyre " is not now accepted by the best English authorities, and is unrecognized in America...}}</ref> while [[A Dictionary of Modern English Usage|Fowler's ''Modern English Usage'']] of 1926 describes that "there is nothing to be said for 'tyre', which is etymologically wrong, as well as needlessly divergent from our own [sc. British] older & the present American usage".<ref name="fowler">{{cite book |last=Fowler |first=H.W. |url= https://books.google.com/books?id=Vr7muDFR6j4C&q=tire+%22there+is+nothing+to+be+said+for+tyre%22&pg=PA655 |title=A Dictionary of Modern English Usage: The Classic First Edition |publisher=Oxford University Press |year=2009 |isbn=978-0-19-953534-7 |editor=David Crystal |page=655 |access-date=2024-01-18}}</ref> However, over the 20th century, ''tyre'' became established as the standard British spelling.<ref name="oed">"tire, n.2." OED Online. Oxford University Press, December 2016. Web. 26 January 2017.</ref>

==History==
[[File:John Boyd Dunlop (c1915).jpg|thumb|upright| [[John Boyd Dunlop]] on a bicycle, {{c.|1915}}]]
[[File:The Employment of Women in Britain, 1914-1918 Q28265.jpg|thumb|upright|Factory workers making tires, 1918]]
The earliest tires were bands of [[leather]] in [[Sumer]],<ref>{{cite book |last=Bertman |first=Stephen |url= https://books.google.com/books?id=1C4NKp4zgIQC&q=ancient+mesopotamian+leather+tires&pg=PA35 |title=Handbook to Life in Ancient Mesopotamia |publisher=Oxford University Press |year=2005 |isbn=9780195183641 |page=35 |access-date=2014-08-02}}</ref> then [[iron]] (later [[steel]]) placed on wooden wheels used on carts and [[wagon]]s. A skilled worker, known as a [[wheelwright]], would cause the tire to expand by heating it in a [[forge]] fire, placing it over the wheel, and quenching it, causing the metal to contract back to its original size to fit tightly on the wheel.

The first patent for what appears to be a standard pneumatic tire appeared in 1847 and was lodged by Scottish inventor [[Robert William Thomson]].<ref>{{cite web |url=http://v3.espacenet.com/origdoc?DB=EPODOC&IDX=US5104&F=0&QPN=US5104 |title=Original document: US5104 (A) ― 1847-05-08 - R.W. Thompson Carriage Wheel |work=Espacenet patent search |access-date=6 December 2023 }}{{Dead link|date=September 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> However, this idea never went into production. The first practical pneumatic tire was made in 1888 on May Street, [[Belfast]], by Scots-born [[John Boyd Dunlop]], owner of one of Ireland's most prosperous veterinary practices. It was an effort to prevent the headaches of his 10-year-old son Johnnie while riding his [[tricycle]] on rough pavements. His doctor, John, later Sir John Fagan, had prescribed cycling as an exercise for the boy and was a regular visitor. Fagan participated in designing the first pneumatic tires. Cyclist [[Willie Hume]] demonstrated the supremacy of Dunlop's tires in 1889, winning the tire's first-ever races in Ireland and then England.<ref>{{cite web|url= http://www.thepedalclub.org/archives/goldenbook/u-z/WilliamHume.html |title=William Hume, 1938 |website=thepedalclub.org |archive-date=3 April 2012 |archive-url= https://web.archive.org/web/20120403120845/http://www.thepedalclub.org/archives/goldenbook/u-z/WilliamHume.html |access-date=3 January 2023}}</ref><ref>{{cite web |url= http://www.dunlop.eu/dunlop_uk/what_sets_dunlop_apart/history/ |title=Technology & Innovation |website=dunlop.eu |url-status=dead |access-date=27 February 2018 |archive-date=2 April 2011 |archive-url= https://web.archive.org/web/20110402192832/http://www.dunlop.eu/dunlop_uk/what_sets_dunlop_apart/history/ }}</ref> In Dunlop's tire patent specification dated 31 October 1888, his interest is only in its use in cycles and light vehicles. In September 1890, he was made aware of an earlier development, but the company kept the information to itself.<ref>{{cite book|first=Arthur |last=Du Cros |author-link=Arthur Du Cros |title=Wheels of Fortune, a salute to pioneers |publisher=Chapman & Hall |location=London |date=1938}}</ref> In 1892, Dunlop's patent was declared invalid because of the prior art by forgotten fellow Scot Robert William Thomson of London (patents London 1845, France 1846, USA 1847). However, Dunlop is credited with "realizing rubber could withstand the wear and tear of being a tire while retaining its resilience".<ref>{{cite book |title=Hutchinson Dictionary of Scientific Biography |last=Dunlop |first=John Boyd |year=2008 |publisher=AccessScience |access-date=9 July 2009 |url= http://www.accessscience.com}}</ref> John Boyd Dunlop and [[Harvey du Cros]] worked through the ensuing considerable difficulties. They employed inventor Charles Kingston Welch and acquired other rights and patents, which allowed them some limited protection of their [[Dunlop Rubber#Pneumatic Tyre|Pneumatic Tyre]] business's position. Pneumatic Tyre would become Dunlop Rubber and [[Dunlop Tyres]]. The development of this technology hinged on myriad engineering advances, including the [[sulfur vulcanization|vulcanization]] of natural rubber using sulfur, as well as the development of the "clincher" rim for holding the tire in place laterally on the wheel rim.

[[Synthetic rubber]]s were invented in the laboratories of [[Bayer]] in the 1920s.<ref name="Ullmann">{{cite book |title=Ullmann's Encyclopedia of Industrial Chemistry |doi=10.1002/14356007.o23_o01 |first1=Werner |last1=Obrecht |first2=Jean-Pierre |last2=Lambert |first3=Michael |last3=Happ |first4=Christiane |last4=Oppenheimer-Stix |first5=John |last5=Dunn |first6=Ralf |last6=Krüger |chapter=Rubber, 4. Emulsion Rubbers |date=2003 |publisher=Wiley-VCH|isbn=978-3-527-30385-4 }}</ref> Rubber shortages in the United Kingdom during WWII prompted research on alternatives to rubber tires with suggestions including leather, compressed asbestos, rayon, felt, bristles, and paper.<ref>{{cite magazine |author=<!--Staff writer(s); The Scribe.--> |date=28 March 1947|title=Tyre Substitutes|magazine=The Autocar |publisher=Iliffe & Sons |location=London |page=736}}</ref>

In 1946, [[Michelin]] developed the [[radial tire]] method of construction. Michelin had bought the bankrupt [[Citroën]] automobile company in 1934 to utilize this new technology. Because of its superiority in handling and fuel economy,<ref name="michelinag.com">{{cite web|url= http://www.michelinag.com/Innovating/Radial-vs.-Bias-technology |title=Radial or bias, the right choice / Properly use your tires - Michelin Agricultural Tires|last=Michelin |website=michelinag.com |language=en-US |access-date=2017-08-04|archive-date=11 July 2016 |archive-url= https://web.archive.org/web/20160711050404/http://www.michelinag.com/Innovating/Radial-vs.-Bias-technology |url-status=dead}}</ref> use of this technology quickly spread throughout Europe and Asia.<ref name="jags.org">{{cite web|url= http://www.jags.org/TechInfo/2001/05May01/tires/historyoftires.htm |title=History |website=jags.org|access-date=12 May 2015|archive-date=6 March 2015|archive-url= https://web.archive.org/web/20150306211250/http://www.jags.org/TechInfo/2001/05May01/tires/historyoftires.htm |url-status=dead}}</ref> In the US, the outdated bias-ply tire construction persisted until the Ford Motor Company adopted radial tires in the early 1970s,<ref>{{cite magazine|url= https://books.google.com/books?id=y-QDAAAAMBAJ&q=%22radial+tire%22+history%5D&pg=PA60 |title=Tires: A century of progress |last=Schultz |first=Mort |date=June 1985 |magazine=Popular Mechanics |pages=60–64 |volume=162 |issue=6 |access-date=2 January 2023 |via=Google Books}}</ref> following a 1968 article in an influential American magazine, ''[[Consumer Reports]]'', highlighting the superiority of radial construction.<ref name="A Tale of Two Tires">{{cite news|url= https://www.bloomberg.com/bw/stories/2006-05-04/a-tale-of-two-tiresbusinessweek-business-news-stock-market-and-financial-advice |title=A Tale of Two Tires |last=Welch |first=Ted |date=May 4, 2006 |work=Bloomberg |access-date=2019-05-05}}</ref><ref>{{cite web|url= https://www.city-journal.org/html/akron-ohio-16038.html |title=Middle City, USA|last=Renn|first=Aaron M.|date=2018-07-16 |newspaper=City Journal |access-date=2019-05-06}}</ref> The US tire industry lost its market share to Japanese and European manufacturers,<ref>{{cite book|url= https://archive.org/details/resistingprotect0000miln |url-access=registration|page=[https://archive.org/details/resistingprotect0000miln/page/151 151] |quote=radial tire market share.|title=Resisting Protectionism: Global Industries and the Politics of International Trade |last=Milner|first=Helen V.|date=1989-09-21|publisher=Princeton University Press |isbn=9780691010748|language=en}}</ref> which bought out US companies.<ref>{{cite book |last=Morris |first=Peter |url=https://drivlu.com/ |title=Cheap Car Tyre |date=2010 |publisher=Berkshire Publishing |pages=2218 |language=en}}</ref>

== Applications ==
<!-- [[OTR]] links to this section -->

Tires may be classified according to the type of vehicle they serve. They may be distinguished by the load they carry and by their application, e.g. to a motor vehicle, aircraft, or bicycle.

=== Automotive ===
==== Light–medium duty ====
[[File:Studded winter tyre.jpg|thumb|Studded winter tire]]
[[File:Studless_tire_2.jpg|thumb|A winter tire without studs, showing tread pattern designed to compact snow in the gaps.<ref>{{cite book|url= https://books.google.com/books?id=NSlSJtEy-NIC&q=siping&pg=PA53|title=Chassis Handbook: Fundamentals, Driving Dynamics, Components, Mechatronics, Perspectives |last1=Heißing |first1=Bernd |last2=Ersoy |first2=Metin |date=2010 |publisher=Springer Science & Business Media |isbn=9783834897893 |pages=591}}</ref>]]
[[File:Rali Portugal (168).JPG|thumb|High-performance [[Rallying|rally]] tires]]

Light-duty tires for passenger vehicles carry loads in the range of {{Convert|250|to|500|kg|lb}} on the drive wheel. Light-to-medium duty trucks and vans carry loads in the range of {{convert|500|to|1500|kg|lb}} on the drive wheel.<ref name="Duffy-2015">{{cite book|url= https://books.google.com/books?id=-iVACgAAQBAJ&q=%22truck+tire%22+%22heavy+duty%22&pg=PA663 |title=Fundamentals of Medium/Heavy Duty Commercial Vehicle Systems |last1=Duffy |first1=Owen C. |last2=Wright |first2=Gus |date=2015-07-20 |publisher=Jones & Bartlett Publishers |isbn=9781284041170 |pages=663–672|language=en}}</ref> They are differentiated by [[Tire code|speed rating]] for different vehicles, including (starting from the lowest speed to the highest): winter tires, light truck tires, entry-level car tires, sedans and vans, sport sedans, and high-performance cars.<ref name=":0A" /> Apart from road tires, there are special categories:

* [[Snow tire]]s are designed for use on [[snow]] and [[ice]]. They have a [[tire tread|tread]] design with larger gaps than those on summer tires, increasing [[Traction (engineering)|traction]] on snow and ice. Such tires that have passed a specific winter traction performance test are entitled to display a "Three-Peak Mountain Snow Flake" symbol on their sidewalls. Tires designed for winter conditions are optimized to drive at temperatures below {{convert|7|°C}}. Some snow tires have metal or ceramic studs that protrude from the tire to increase traction on hard-packed snow or ice. Studs abrade dry pavement, causing dust and creating wear in the wheel path.<ref>{{cite web|url= http://cooper.co.uk/shop/asphalt-testing/prall-tester/|title=Prall Tester - Studded Tyre Wear Test |website=cooper.co.uk |publisher=Cooper Research Technology |access-date=1 September 2014}}</ref> Regulations that require the use of snow tires or permit the use of studs vary by country in Asia and Europe, and by state or province in North America.
* All-season tires are typically rated for mud and snow (M+S). These tires have tread gaps that are smaller than snow tires and larger than conventional tires. They are quieter than snow tires on clear roads, but less capable on snow or ice.<ref>{{cite book|url= https://books.google.com/books?id=9EV9-xiiJzcC&q=m%2Bs+tire+rating&pg=PA35 |title=Wheel and Tire Performance Handbook |last=Newton |first=Richard |date=2007 |publisher=MotorBooks International |isbn=9781610592512 |location=St. Paul |page=35}}</ref>
* All-terrain tires are designed to have adequate traction off-road, yet have benign handling and noise characteristics for highway driving.<ref>{{cite book|url= https://books.google.com/books?id=X95PU39mzSMC&q=%22all-terrain+tire%22&pg=PA17 |title=Jeep 4X4 Performance Handbook |last=Allen |first=Jim |publisher=MotorBooks International|isbn=9781616730536|language=en}}</ref> Such tires are rated better on snow and rain than street tires and "good" on ice, rock, and sand.<ref name="Hanseen-2018">{{Cite book|url= https://books.google.com/books?id=tLJwDwAAQBAJ&q=%22mud+tire%22&pg=PA99 |title=Jeep TJ 1997-2006: How to Build & Modify |last=Hanseen|first=Michael|date=2018-08-15|publisher=CarTech |isbn=9781613254288 |language=en}}</ref>
* Mud-terrain tires have a deeper, more open tread for good grip in mud, than all-terrain tires, but perform less well on pavement.<ref name=":0B" />
* High-performance tires are rated for speeds up to {{Convert|168|mph|km/h|order=flip}} and ultra-high-performance tires are rated for speeds up to {{Convert|186|mph|km/h|order=flip}}, but have harsher ride characteristics and durability.<ref>{{Cite book|url= https://books.google.com/books?id=i2ZmgxbTS3AC&q=%22high-performance+tire%22&pg=PA47 |title=High-Performance Handling for Street or Track |last=Alexander |first=Don |date=2013-02-15|publisher=Motorbooks|isbn=9780760339947|language=en}}</ref>
* Electric vehicles have unique demands on tires due to the combination of weight (resulting in new load index), higher torque, and requirements for lower rolling resistance.<ref>{{cite news |last1=Gitlin |first1=Jonathan M. |title=Electric vehicles ask a lot of their tires—here's why |url= https://arstechnica.com/cars/2021/12/why-electric-vehicle-tires-are-challenging-to-make/ |access-date=22 December 2021 |work=Ars Technica |date=16 December 2021}}</ref>

Other types of light-duty automotive tires include run-flat tires and race car tires:

* [[Run-flat tire]]s eliminates the need for a spare tire because they can be traveled on at a reduced speed in the event of a puncture, using a stiff sidewall to prevent damage to the tire rim.<ref name="Erjavec-2005">{{cite book|url= https://books.google.com/books?id=U4TBoJB2zgsC&q=%22run-flat+tire%22&pg=RA8-PP26 |title=Automotive Technology: A Systems Approach|last=Erjavec|first=Jack|date=2005|publisher=Cengage Learning |isbn=9781401848316 |pages=1100 |language=en}}</ref> Vehicles without run-flat tires rely on a spare tire, which may be a compact tire, to replace a damaged tire.<ref name="Erjavec-2005" />
* Race car tires come in three main categories, ''DOT'' (street-legal), ''slick'', and ''rain''. Race car tires are designed to maximize cornering and acceleration friction at the expense of longevity. Racing slicks have no tread to maximize contact with the pavement and rain tires have channels to eject water to avoid [[Aquaplaning|hydroplaning]].<ref>{{cite book|url= https://books.google.com/books?id=9EV9-xiiJzcC&q=%22Wheel+and+Tire+Performance+Handbook%22 |title=Wheel and Tire Performance Handbook |last=Newton |first=Richard |publisher=MotorBooks International|isbn=9781610592512|pages=52|language=en}}</ref>

==== Heavy duty ====
[[File:Gianttires ontruck.jpg|thumb|Off-road tires under transport]]

Heavy-duty tires for large trucks and buses come in a variety of profiles and carry loads in the range of {{Convert|1800|to|2500|kg|lb}} on the drive wheel.<ref name="Duffy-2015" /> These are typically mounted in tandem on the drive axle.<ref name="Erjavec-2005" />

* Truck tires come in a variety of profiles that include "low profile" with a section height that is 70 to 45% of the tread width, "wide-base" for heavy vehicles, and a "super-single" tire that has the same total contact pressure as a dual-mounted tire combination.<ref name="Erjavec-2005" />
* Off-road tires are used on construction vehicles, agricultural and forestry equipment, and other applications that take place on soft terrain. The category also includes machinery that travels over hardened surfaces at industrial sites, ports, and airports.<ref>{{cite book|url= https://books.google.com/books?id=XXYYI-vFyrwC&q=%22Off-the-Road%22+tires|title=Certain Off-the-Road Tires from China|last=Haines|first=Elizabeth|publisher=U.S. International Trade Commission|isbn=9781457817304|edition=701-TA-448 and 731-TA-1117|pages=4|language=en}}</ref> Tires designed for soft terrain have a deep, wide tread to provide traction in loose dirt, mud, sand, or gravel.<ref>{{cite web |url=https://industrialjournalism.com/2019/05/08/global-off-the-road-tire-market-development-history-current-analysis-and-estimated-forecast-to-2025/ |title=Global Off The Road Tire Market: Development History, Current Analysis and Estimated Forecast to 2025 |date=May 8, 2019 |work=Industrial Journalism |access-date=2019-05-09 |archive-date=22 August 2025 |archive-url=https://web.archive.org/web/20250822022025/https://industrialjournalism.com/2019/05/08/global-off-the-road-tire-market-development-history-current-analysis-and-estimated-forecast-to-2025/ |url-status=dead }}</ref>

=== Other ===
Aircraft, bicycles, and a variety of industrial applications have distinct design requirements.[[File:Boeing-777-300 chassis .jpg|thumb|Tires on the wheels of a [[Bogie#Bogie (aircraft)|bogie]] on a [[Boeing 777]]]]

* [[Aircraft tire|Aircraft tires]] are designed for landing on paved surfaces and rely on their [[landing gear]] to absorb the shock of landing. To conserve the weight and space required, they are typically small in proportion to the vehicle that they support. Most are radial-ply construction. They are designed for a peak load when the aircraft is stationary, although side loads upon landing are an important factor.<ref>{{cite book|url= https://books.google.com/books?id=XMpdOeWeqq8C&q=%22Aircraft+Landing+Gear+Design%3A+Principles+and+Practices%22 |title=Aircraft Landing Gear Design: Principles and Practices|last=Currey|first=Norman S. |date=1988 |publisher=AIAA |isbn=9781600860188 |pages=123–5 |language=en}}</ref> Although hydroplaning is a concern for aircraft tires, they typically have radial grooves and no lateral grooves or sipes.<ref>{{cite book|url= https://books.google.com/books?id=urE7AAAAMAAJ&q=%22Aerospace+safety%22+tires&pg=RA1-PT10|title=Aerospace safety |last=McKenny |first=Earl F.|date=May 1964|publisher=United States Dept of the Air Force |location=Washington, DC |pages=5–7 |language=en}}</ref> Some light aircraft employ large-diameter, low-pressure [[tundra tire]]s for landing on unprepared surfaces in wilderness areas.<ref>{{cite book|url= https://books.google.com/books?id=r9o_4EmCsvkC&q=%22Tundra+tire%22&pg=PA88|title=Tundra Tire Nation |last=Richfield |first=Paul J. |date=September 2005 |publisher=Flying Magazine |location=New York|pages=88–92 |language=en}}</ref>
* [[Bicycle tire]]s may be designed for riding on roads or over unimproved terrain and may be mounted on vehicles with more than two wheels. There are three main types: ''clincher'', ''wired'' and ''tubular''.<ref>Sharp, Archibald, Bicycles & Tricycles: An Elementary Treatise on Their Design and Construction, Longmans Green, London and New York, 1896, pages 494–502; reprinted by MIT Press, 1977, {{ISBN|0-262-69066-7}}</ref> Most bicycle tires are ''clincher'' and have a bead that presses against the wheel rim. An inner tube provides the air pressure and the contact pressure between the bead and wheel rim.<ref>{{cite web|url= http://www.sheldonbrown.com/rinard/tirebead.htm |title=Tire Bead Test |first=Damon |last=Rinard |year=2000 |website=sheldonbrown.com |access-date=March 10, 2013 |quote=Conclusion: Clincher tires stay on the rim primarily by the clinch of the hooked sidewall that retains the tire bead, not the circumferential tension in the bead.}}</ref>
* Industrial tires support such vehicles as forklifts, tractors, excavators, road rollers, and bucket loaders. Those used on smooth surfaces have a smooth tread, whereas those used on soft surfaces typically have large tread features.<ref>{{cite web|url= https://markettalknews.com/industrial-tire-market-size-estimated-to-observe-significant-growth-by-2018-2026/|title=Industrial Tire Market: Size Estimated To Observe Significant Growth By 2018 – 2026 |last=Jinkya|first=A.|date=May 10, 2019|website=Market Talk News|language=en-US|access-date=2019-05-10|url-status= usurped|archiveurl= https://web.archive.org/web/20190510142205/https://markettalknews.com/industrial-tire-market-size-estimated-to-observe-significant-growth-by-2018-2026/|archivedate=2019-05-10}}</ref> Some industrial tires are solid or filled with foam.<ref>{{cite book|url= https://books.google.com/books?id=NQDnPgAACAAJ&q=%22industrial+tire%22|title=Industrial Press-on Solid Rubber Tires: Exported Into Canada by Bearcat Tire Company, Chicago, Illinois, United States of America|last=Tribunal|first=Canada Anti-dumping|date=1971|publisher=Information Canada|language=en}}</ref>
* [[Motorcycle tire]]s provide traction, resisting wear, absorbing surface irregularities, and allow the [[motorcycle]] to turn via [[countersteering]]. The two tires' contact with the ground affects safety, braking, fuel economy, noise, and rider comfort.<ref name="Cossalter">{{cite book | title = Motorcycle Dynamics | edition = Second | last = Cossalter | first = Vittore | year = 2006 | publisher = Lulu.com | isbn = 978-1-4303-0861-4 | pages = 37–72 }}{{self-published source|date=February 2020}}</ref>{{self-published inline|date=February 2020}}

==Construction types==
[[File:Tire plies.png|thumb|A cross-section of a tire showing ply orientations]]

Tire construction spans [[Pneumatics|pneumatic]] tires used on cars, trucks, and aircraft, but also includes non-automotive applications with slow-moving, light-duty, or railroad applications, which may have non-pneumatic tires.

===Automotive===
Following the 1968 ''[[Consumer Reports]]'' announcement of the superiority of the radial design, [[radial tire]]s began an inexorable climb in market share, reaching 100% of the North American market in the 1980s.<ref name="A Tale of Two Tires" /> Radial tire technology is now the standard design for essentially all automotive tires, but other methods have been used.<ref name=":0A" />

Radial (or radial-ply) tire construction utilizes body ply cords extending straight across the tread from bead to bead—so that the cords are laid at approximately right angles to the centerline of the tread, and parallel to one another—as well as stabilizer belts directly beneath the tread. The plies are generally made of nylon, polyester, or steel, and the belts of steel, fiberglass, or [[Kevlar]].<ref>{{cite web |url=https://agtiretalk.com/tire-casing-construction-poly-vs-nylon-vs-steel/ |title=Tire Casing Construction: Poly Vs Nylon Vs Steel |last=Tuschner |first=James |date=30 August 2021 |website=AG Tire Talk |access-date=11 September 2024}}</ref><ref>{{cite web |url=https://tiregrades.com/tire-anatomy/what-is-a-radial-tire/ |title=What Is a Radial Tire? |last=Creech |first=Will |date=12 May 2023 |website=TireGrades |access-date=27 July 2024}}</ref> The tire's footprint, wider than a bias tire's, and flexible sidewalls provide a better grip in turns, and its circumferential belts stabilize it. The advantages of this construction over that of a bias tire are many, including longer tread life, better steering control, lower [[rolling resistance]], improved fuel economy, more uniform wear, higher heat resistance, fewer blowouts, and a steadier, more comfortable ride at speed. Disadvantages, besides a higher cost than that of bias tires, are a harder ride at low speeds and generally worse performance on rough terrain.<ref name="Holman">{{cite web |url=https://www.motortrend.com/how-to/129-1102-tire-construction-technology-bias-and-radial/ |title=Tire Construction Technology: Bias and Radial |last=Holman |first=Sean |date=1 February 2011 |website=MotorTrend |access-date=10 September 2024}}</ref><ref>{{cite web |url=https://mechanicinsider.com/radial-vs-bias-ply/ |title=Radial vs Bias Ply – Debate Ends Here! |last=Smith |first=David |website=Mechanic Insider |date=26 July 2020 |access-date=7 September 2024 |archive-date=24 July 2021 |archive-url=https://web.archive.org/web/20210724140756/https://mechanicinsider.com/radial-vs-bias-ply/ |url-status=dead }}</ref><ref name=":0A" /> Radial tires are also seldom seen in diameters of greater than 42 inches, as such tires are difficult to make.<ref>{{cite web |url=https://www.intercotire.com/comparing_bias_ply_radial_tires_trent_mcgee |title=Comparing Bias Ply to Radial Tires |last=McGee |first=Trent |website=Interco Tire Corporation |access-date=27 July 2024 |archive-date=3 August 2024 |archive-url=https://web.archive.org/web/20240803223416/https://www.intercotire.com/comparing_bias_ply_radial_tires_trent_mcgee |url-status=dead }}</ref>

{{vanchor|Bias}} tire (bias-ply, or cross-ply) construction utilizes body ply cords that extend diagonally from bead to bead, usually at angles in the range of 30 to 40 degrees from the direction of travel.<ref>{{cite web |url=https://help.summitracing.com/knowledgebase/article/SR-04654/en-us |website=Summit Racing Equipment |access-date=10 September 2024|title=What's the difference between radial and bias ply tires? · Help Center}}</ref> Successive plies are laid at opposing angles, forming a crisscross pattern to which the tread is applied. Such a design is resistant to sidewall deformation and punctures (and to punctures’ expansion, or "torque splitting") and therefore durable in severe use.<ref>{{cite web |url=https://whirlingwheelz.com/radial-vs-bias-ply-tires/ |title=Radial vs. Bias Ply Tires: Pros & Cons, Differences & Which to Choose |last=Niklas |date=9 March 2022 |website=Whirling Wheelz |access-date=14 September 2024 |archive-date=15 September 2024 |archive-url=https://web.archive.org/web/20240915032650/https://whirlingwheelz.com/radial-vs-bias-ply-tires/ |url-status=dead }}</ref> Since the tread and sidewalls share their casing plies, the tire body flexes as a whole, providing the main advantage of this construction, better traction and smoother motion on uneven surfaces, with a greater tendency to conform to rocky ground and throw off mud and clay, especially because the rubber is usually of a softer compound than that used on radial tires. However, this conformity increases a bias tire's rolling resistance, and its stiffness allows less control, [[traction (engineering)|traction]], and comfort at higher speeds, while [[Shearing (physics)|shear]] between its overlapping plies causes friction that generates heat.<ref name="Holman"/><ref>{{cite web |url=https://www.mudthrowers.com/bias_vs_radial_tires |title=Bias vs Radial Construction |website=Mudthrowers |access-date=10 September 2024}}</ref><ref>{{cite web |title=Why should I choose bias ply tires? |url=https://help.summitracing.com/knowledgebase/article/SR-04655/en-us |access-date=10 September 2024 |website=Summit Racing Equipment}}</ref><ref name=":0A" /> Still, bias tires benefit from simpler structure and so cost less than like-size radials, and they remain in use on heavy equipment and off-road vehicles, although the earthmoving market has shifted to radials.<ref name=":0A" /><ref>{{cite web |url=https://www.constructionequipment.com/trucking/article/10708762/how-off-road-radials-are-changing-earthmoving |title=How Off-Road Radials Are Changing Earthmoving |last=Stewart |first=Larry |date=28 September 2010 |website=Construction Equipment |access-date=10 September 2024}}</ref>

A belted bias tire starts with two or more bias plies to which stabilizer belts are bonded directly beneath the tread. This construction provides a smoother ride that is similar to the bias tire, while lessening rolling resistance because the belts increase tread stiffness. The design was introduced by Armstrong, while Goodyear made it popular with the "[[Goodyear Polyglas tire|Polyglas]]" trademark tire featuring a polyester carcass with belts of fiberglass.<ref name="pliesandangles">{{cite magazine|date=March 1972|title=Plies and angles - see how they run|url= https://books.google.com/books?id=LtUDAAAAMBAJ&q=Plies+and+angles+-+see+how+they+run+Until+1967+U.S.+tiremakers&pg=PA61 | magazine=Popular Mechanics |volume=136 |issue=3 |page=62 |access-date=13 March 2014}}</ref> The "belted" tire starts two main plies of polyester, rayon, or nylon annealed as in conventional tires, and then placed on top are circumferential belts at different angles that improve performance compared to non-belted bias tires. The belts may be fiberglass or steel.<ref name="pliesandangles" />

===Other===
[[File:2005 091112-28rim0051 compressed.JPG|thumb|[[Airless tire]]]]
[[Tubeless tire]]s are pneumatic tires that do not require a separate [[#On the wheel|inner tube]].

Semi-pneumatic tires have a hollow center, but they are not pressurized. They are lightweight, low-cost, puncture-proof, and provide cushioning.<ref>{{cite magazine|last=Jones|first=Thomas H. |year=1980 |title=Get things moving with casters, glides, and wheels |magazine=Popular Science |volume=216 |issue=5 |page=148 |issn=0161-7370}}</ref> These tires often come as a complete assembly with the wheel and even integral [[ball bearing]]s. They are used on [[lawn mower]]s, [[wheelchair]]s, and [[wheelbarrow]]s. They can also be rugged, typically used in industrial applications,<ref>{{cite web|url= http://www.thomasnet.com/products/semipneumatic-wheels-93980407-1.html |title=Thomas Net sources for industrial use 'Semi-Pneumatic Wheels'|publisher=Thomasnet.com |access-date=2010-10-23|archive-date=17 July 2011 |archive-url= https://web.archive.org/web/20110717051419/http://www.thomasnet.com/products/semipneumatic-wheels-93980407-1.html |url-status=dead}}</ref> and are designed to not pull off their [[Rim (wheel)|rim]] under use.

An [[airless tire]] is a non-pneumatic tire that is not supported by air pressure. They are most commonly used on small vehicles, such as golf carts, and on utility vehicles in situations where the risk of puncture is high, such as on construction equipment. Many tires used in industrial and commercial applications are non-pneumatic, and are manufactured from solid rubber and plastic compounds via molding operations. Solid tires include those used for lawnmowers, skateboards, golf carts, [[Kick scooter|scooters]], and many types of light industrial vehicles, carts, and trailers. One of the most common applications for solid tires is for material handling equipment (forklifts). Such tires are installed utilizing a hydraulic tire press.

[[Wheelwright|Wooden wheels]] for horse-drawn vehicles usually have a [[wrought iron]] tire. This construction was extended to wagons on horse-drawn tramways, rolling on [[Haytor Granite Tramway|granite setts]] or [[plateway|cast iron rails]].

The wheels of some railway engines and older types of rolling stock are fitted with [[railway tires]] to prevent the need to replace the entirety of a wheel. The tire, usually made of steel, surrounds the wheel and is primarily held in place by [[interference fit]].

Aircraft tires may operate at pressures that exceed {{convert|200|psi|kPa bar psi|lk=on|order=out}}.<ref>{{cite book|last=Fabre|first=C.|title=Bearing capacity of roads, railways and airfields: proceedings of the 8th International Conference on the Bearing Capacity of Roads and Airfields, Champaign, Illinois, USA, June 29-July 2, 2009|date=2009| publisher=CRC Press/Balkema|isbn=978-0-203-86528-6|editor-last=Tutumluer|editor-first=Erol |location=Leiden, Netherlands |pages=1405 |oclc=636611702 |editor-last2=Al-Qadi |editor-first2=Imad L.}}</ref> Some aircraft tires are inflated with [[nitrogen]] to "eliminate the possibility of a chemical reaction between atmospheric oxygen and volatile gases from the tire inner liner producing a tire explosion".<ref>{{cite web |url= http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/55850e6389efba3c8625695b006723a3!OpenDocument#_Section1 |title= FAA Airworthiness Directive |access-date= 2013-06-15 |archive-date= 2 February 2017 |archive-url= https://web.archive.org/web/20170202053815/http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/55850e6389efba3c8625695b006723a3!OpenDocument#_Section1 |url-status= dead }}</ref>

== Manufacturing ==
{{Main|Tire manufacturing}}

Pneumatic tires are manufactured in about 450 tire factories around the world. Tire production starts with bulk raw materials such as rubber, carbon black, and chemicals and produces numerous specialized components that are assembled and cured. Many kinds of rubber are used, the most common being [[styrene-butadiene]] [[copolymer]].<ref>{{Cite book|last=Rodgers|first=Brendan|url= https://books.google.com/books?id=K_r1DwAAQBAJ&q=tire+materials+used|title=Tire Engineering: An Introduction|date=2020-09-28|publisher=CRC Press|isbn=978-1-000-19055-7|language=en}}</ref>

Forecasts for the global automotive tire market indicate continued growth through 2027. Estimates put the value of worldwide sales volume around $126 billion in 2022, it is expected to reach the value of over $176 billion by 2027.<ref>{{cite web|url= https://www.statista.com/statistics/1228044/global-automotive-tire-market-size/ |title=Size of the global automotive tire market from 2022 to 2027 |website=statista.com |first=Martin |last=Placek |date=8 June 2023 |access-date=31 January 2024}}</ref> Production of tires is also experiencing growth. In 2015, the US manufactured almost 170 million tires.<ref>{{cite web|last1=Davis |first1=Bruce |title=2015 was strong year for U.S. tire industry |url= http://www.tirebusiness.com/article/20160217/NEWS/160219928|website=Tire Business |date=17 February 2016|publisher=Crain Communications |access-date=13 December 2016}}</ref> Over 2.5 billion tires are manufactured annually, making the tire industry a major consumer of natural rubber. It was estimated that for 2019 onwards, at least 3 billion tires would be sold globally every year.<ref name="freedonia2019">{{cite web|title=World Tires|url= https://www.freedoniagroup.com/industry-study/world-tires-3357.htm |website=freedoniagroup.com |access-date=19 May 2017}}</ref> However, other estimates put worldwide tire production of 2,268 million in 2021 and is predicted to reach 2,665 million tires by 2027.<ref>{{cite web|url= https://oem.news/industry/rubber/tire/tire-market-the-global-tire-industry-analysis/ |title=Tire Market: The Global Tire Industry Analysis |first=CP |last=Raj |date=28 November 2022 |website=oem.news |access-date=31 January 2024}}</ref>

As of 2011, the top three tire manufacturing companies by revenue were [[Bridgestone]] (manufacturing 190 million tires), [[Michelin]] (184 million), [[Goodyear Tire and Rubber Company|Goodyear]] (181 million); they were followed by [[Continental AG|Continental]], and [[Pirelli]].<ref>{{citation |url= http://www.companiesandmarkets.com/Market-Report/research-report-on-worlds-top-50-tire-enterprises,-2010-2011-454329.asp |archive-url= https://web.archive.org/web/20110120010101/http://www.companiesandmarkets.com/Market%2DReport/research%2Dreport%2Don%2Dworlds%2Dtop%2D50%2Dtire%2Denterprises%2C%2D2010%2D2011%2D454329.asp|archive-date= January 20, 2011 |title= Research Report on World's Top 50 Tire Enterprises, 2010-2011 Market Research Report |date=December 2, 2010 |website=companiesandmarkets.com |url-status= dead |publisher=Vertical Edge Limited }}</ref><ref name=Statista>{{Citation |url= https://www.statista.com/statistics/225677/revenue-of-the-leading-tire-producers-worldwide/ |title=The world's largest tire manufacturers in Q1 and Q2 2016, based on tire-related sales (in billion U.S. dollars) |website=statista.com |year= 2016 }}</ref> The [[Lego]] group produced over 318 million [[Lego tire|toy tires]] in 2011 and was recognized by [[Guinness World Records]] as having the highest annual production of tires by any manufacturer.<ref name="rubber world">{{cite magazine |title=Shift of emphasis |magazine=Rubber World |date=1 April 2012|url= http://www.thefreelibrary.com/Shift+of+emphasis.-a0289215925}}</ref><ref>{{cite book |last=Cook |first=David |title=Robot Building for Beginners |publisher=Apress |edition=Third |date=2015 |page=458 |url= https://books.google.com/books?id=iHiBCgAAQBAJ&q=Guinness+world+record+lego+tires&pg=PA445 |isbn = 9781484213599 }}</ref>

===Components===
[[File:Tire components -- NHTSA The Pneumatic Tire.png|thumb|Components of a radial tire]]
[[File:Mountain bike tires.JPG|thumb|Mountain bicycle tires with an open-lug pattern for grip in soft soil]]
[[File:F1 Slick Tires.jpg|thumb|Absence of grooves maximizes dry-pavement friction on a set of slick [[Formula One tyres|Formula One tires]]]]
A tire comprises several components: the tread, bead, sidewall, shoulder, and ply.

====Tread====
The [[tire tread|tread]] is the part of the tire that comes in contact with the road surface. The portion that is in contact with the road at a given instant in time is the [[contact patch]]. The tread is a thick rubber, or rubber/composite compound formulated to provide an appropriate level of traction that does not wear away too quickly.<ref>{{Cite book|url= https://books.google.com/books?id=z7bd-KlznuEC&q=what+is+tire+tread |title=Frictional Interaction of Tire and Pavement|last=Meyer|first=W. E. |date=1983 |publisher=ASTM International|language=en}}</ref>

The tread pattern is characterized by a system of circumferential grooves, lateral sipes, and slots for road tires<ref name=":0A">{{Cite book |title=The Pneumatic Tire |last1=Gent |first1=Alan N. |last2=Walter |first2=Joseph D. |publisher=National Highway Transportation Safety Administration |year=2006 |series=DOT HS 810 561 |location=Washington, DC |url= https://www.nhtsa.gov/staticfiles/safercar/pdf/PneumaticTire_HS-810-561.pdf |access-date=3 May 2019 |archive-date=9 March 2021 |archive-url= https://web.archive.org/web/20210309162555/https://www.nhtsa.gov/staticfiles/safercar/pdf/PneumaticTire_HS-810-561.pdf |url-status=dead }}</ref> or a system of lugs and [[wikt:void|voids]] for tires designed for soft terrain or snow. Grooves run circumferentially around the tire and are needed to channel away water. Lugs are that portion of the tread design that contacts the road surface. Grooves, sipes, and slots allow tires to evacuate water.

The design of treads and the interaction of specific tire types with the roadway surface affects [[roadway noise]], a source of [[noise pollution]] emanating from moving vehicles. These sound intensities increase with higher vehicle speeds.<ref>{{cite journal|last=Hogan|first=C. Michael|date=September 1973 |title=Analysis of highway noise |journal=Journal of Water, Air, & Soil Pollution |publisher=Springer Verlag |volume=2 |issue=3 |pages=387–392 |doi=10.1007/BF00159677 |issn=0049-6979|bibcode=1973WASP....2..387H|s2cid=109914430}}</ref> Tires treads may incorporate a variety of distances between slots (''pitch lengths'') to minimize noise levels at discrete frequencies. Sipes are slits cut across the tire, usually perpendicular to the grooves, which allow the water from the grooves to escape sideways and mitigate [[Hydroplaning (tires)|hydroplaning]].<ref name=":0A" />

Different tread designs address a variety of driving conditions. As the ratio of tire tread area to groove area increases, so does tire friction on dry pavement, as seen on [[Formula One tyres|Formula One tires]], some of which have no grooves. High-performance tires often have smaller void areas to provide more rubber in contact with the road for higher traction, but may be compounded with softer rubber that provides better traction, but wears quickly.<ref>{{cite web|url= https://www.hemmings.com/blog/2013/08/12/montjuic-1971-when-formula-1-met-racing-slicks/ |title=Montjuic, 1971: When Formula 1 met racing slicks |last=Ernst |first=Kurt |date=August 12, 2013 |work=Hemmings Daily |access-date=2019-05-01}}</ref> Mud and snow (M&S) tires employ larger and deeper slots to engage mud and snow.<ref name=":0A" /> [[Snow tire]]s have still larger and deeper slots that compact snow and create shear strength within the compacted snow to improve braking and cornering performance.<ref name="Hays2">{{cite book|url= https://books.google.com/books?id=rEL2BwAAQBAJ&q=shear+strength+snow+tire&pg=PA107 |title=The Physics of Tire Traction: Theory and Experiment |last=Hays |first=Donald |date=2013 |publisher=Springer Science & Business Media |isbn=9781475713701 |pages=428 |access-date=2016-12-25}}</ref>

Wear bars (or wear indicators) are raised features located at the bottom of the tread grooves that indicate the tire has reached its wear limit. When the tread lugs are worn to the point that the wear bars connect across the lugs, the tires are fully worn and should be taken out of service, typically at a remaining tread depth of {{convert|1.6|mm|in}}.<ref>{{cite book|url= https://books.google.com/books?id=-iVACgAAQBAJ&q=tire+wear+bar&pg=PA679|title=Fundamentals of Medium/Heavy Duty Commercial Vehicle Systems |last1=Duffy |first1=Owen C.|last2=Wright|first2=Gus|date=2015-07-20|publisher=Jones & Bartlett Publishers |isbn=9781284041170 |pages=678|language=en}}</ref>

====Other====
The [[tire bead]] is the part of the tire that contacts the [[rim (wheel)|rim]] on the wheel. This essential component is constructed with robust steel cables encased in durable, specially formulated rubber designed to resist stretching. The precision of the bead's fit is crucial, as it seals the tire against the wheel, maintaining air pressure integrity and preventing any loss of air. The bead's design ensures a secure, non-slip connection, preventing the tire from rotating independently from the wheel during vehicle motion. Additionally, the interplay between the bead's dimensions and the wheel's width significantly influences the vehicle's steering responsiveness and stability, as it helps to maintain the tire's intended shape and contact with the road.

{{anchor|Sidewall}}The sidewall is that part of the tire, or [[Bicycle tire#Sidewall|bicycle tire]], that bridges between the tread and bead. The sidewall is largely rubber but reinforced with fabric or steel cords that provide for tensile strength and flexibility. The sidewall contains air pressure and transmits the torque applied by the drive axle to the tread to create traction but supports little of the weight of the vehicle, as is clear from the total collapse of the tire when punctured.

Sidewalls are molded with manufacturer-specific detail, government-mandated warning labels, and other consumer information.<ref>{{cite web |title=Reading a Tire Sidewall |url= https://www.tireindustry.org/resources/consumer-education/consumer-safety-overview/reading-a-tire-sidewall/ |work=Tire Industry Association |access-date=6 December 2023}}</ref><ref>{{cite web |last1=Hall |first1=Emme |title=How to read a tire sidewall |url= https://www.cnet.com/roadshow/news/how-to-read-a-tire-sidewall/ |work=CNET |date=2 October 2019 |access-date=6 December 2023}}</ref>

Sidewall may also have sometimes decorative ornamentation that includes [[whitewall tire|whitewall]] or red-line inserts as well as [[tire lettering]].<ref>{{cite web |last1=Vranas |first1=Chuck |title=Whitewall Tires 101: How They're Made and Why They're Cool |url= https://www.motortrend.com/how-to/whitewall-tires-101-how-theyre-made-and-why-theyre-cool/ |work=Motor Trend |date=24 July 2017 |access-date=6 December 2023}}</ref>

The shoulder is that part of the tire at the edge of the tread as it makes the transition to the sidewall.<ref>{{cite web|title=Tire Structure |url= https://www.hankooktire.com/us/services-tips/tire-guide/structure.html |website=hankooktire.com/us/ |date = nd |access-date=27 October 2021}}</ref>

[[Ply (layer)|Plies]] are layers of relatively inextensible cords embedded in the rubber<ref>{{cite book| url= https://books.google.com/books?id=Pvsv78xj7UIC&q=ply |title=Vehicle dynamics: theory and applications |first=Reza N. |last=Jazar |publisher=Springer |quote=Inner layers are made of different fabrics, called plies. |year=2008 |page=11 |isbn=978-0-387-74243-4 |access-date=2011-03-16}}</ref> to hold its shape by preventing the rubber from stretching in response to the internal pressure. The orientations of the plies play a large role in the performance of the tire and are one of the main ways that tires are categorized.<ref>{{cite web|url= https://www.tdotperformance.ca/auto-parts-canada/winter-tires-faq-how-to-guide |title=Winter Tires: FAQs & How To's |publisher=TDot Performance |access-date=2020-04-16}}</ref>

=== Blems ===
Blem (short for "blemished") is a term used for a tire that failed inspection during manufacturing - but only for superficial/cosmetic/aesthetic reasons. For example, a tire with white painted lettering which is smudged or incomplete might be classified as a "blem". Blem tires are fully functional and generally carry the same warranty as flawless tires - but are sold at a discount.<ref>{{cite web|url=https://www.intercotire.com/blem_list_0|title=What is a Blem?|website=intercotire.com|access-date=2023-03-05|archive-date=6 March 2023|archive-url=https://web.archive.org/web/20230306012800/https://www.intercotire.com/blem_list_0|url-status=dead}}</ref>

=== Materials ===
The materials of modern pneumatic tires can be divided into two groups, the cords that make up the ply and the [[elastomer]] which encases them.

====Cords====
The cords, which form the ply and bead and provide the tensile strength necessary to contain the inflation pressure, can be composed of [[steel]], natural fibers such as [[cotton]] or [[silk]], or synthetic fibers such as [[nylon]] or [[kevlar]]. Good adhesion between the cords and the rubber is important. To achieve this the steel cords are coated in a thin layer of brass,<ref>{{cite journal |last1=Vanooij |first1=William J. |last2=Harakuni |first2=Prasan B. |last3=Buytaert |first3=Guy |title=Adhesion of Steel Tire Cord to Rubber |journal=Rubber Chemistry and Technology |date=1 July 2009 |volume=82 |issue=3 |pages=315–339 |doi=10.5254/1.3548251}}</ref> various additives will also be added to the rubber to improve binding, such as [[resorcinol]]/[[Hexamethoxymethylmelamine|HMMM]] mixtures.

====Elastomer====
[[File:ESBR.png|thumb|About 50% of tires use the [[styrene-butadiene]] copolymer as a primary ingredient<ref name="Ullmann" />]]

The elastomer, which forms the [[#Tread|tread]] and encases the cords to protect them from abrasion and hold them in place, is a key component of pneumatic tire design. It can be composed of various composites of rubber material&nbsp;– the most common being [[styrene-butadiene]] copolymer&nbsp;– with other chemical compounds such as [[Silicon dioxide|silica]] and [[carbon black]].

Optimizing [[rolling resistance]] in the elastomer material is a key challenge for reducing fuel consumption in the transportation sector. It is estimated that passenger vehicles consume approximately 5%–15% of their fuel to overcome rolling resistance, while the estimate is understood to be higher for heavy trucks.<ref>{{cite web|url= http://www.afdc.energy.gov/conserve/fuel_economy_tires_light.html |title=Alternative Fuels Data Center: Low Rolling Resistance Tires |website=afdc.energy.gov| access-date=2015-10-31}}</ref> However, there can be a trade-off between rolling resistance and wet traction and grip, based on the viscoelastic properties of the rubber compound.  A low [[dissipation factor]], which is often written as the tangent of the phase angle delta (tan(''δ'')), reduces rolling resistance, whereas a high tan(''δ'') can improve wet traction and grip.  Fortunately, this tradeoff is not inherent: rolling resistance is affected by tan(''δ'') at low frequencies (on the order of 100&nbsp;Hz) whereas the improvement in traction comes from high tan(''δ'') at much higher frequencies.  Historically, direct measurement of tan(''δ'') at high frequencies was difficult, and it became common to instead use measured low-frequency tan(''δ'') at a low temperature (0&nbsp;°C) as a predictor of wet traction because of its correlation to high-frequency tan(''δ''). For rolling resistance, tan(''δ'') value at 60&nbsp;°C is directly relevant and often used as a predictor of low rolling resistance. 
<ref> "Structure and properties of tire rubbers prepared by anionic polymerization," Aggarwal, S. L., Hargis, I. G., Livigni, R. A., Fabris, H. J., & Marker, L. F.  In Advances in Elastomers and Rubber Elasticity, pp. 17–36, 1986,
https://link.springer.com/content/pdf/10.1007/978-1-4757-1436-4_2?pdf=chapter+toc </ref>
<ref name=":0B">"Dynamic Mechanical Properties Of Passenger And Light Truck Tire Treads". Report No. '''DOT''' '''HS''' '''811 270.''' National Highway Traffic Safety Administration, U.S. Department of Transportation. '''2010.'''</ref> 

Designing an elastomer material that can achieve both high wet traction and low rolling resistance is key in achieving safety and fuel efficiency in the transportation sector.  More recent research has found that compounds using dual-phase fillers exhibit a poor correlation between low-temperature tan(''δ'') and wet traction, indicating an opportunity to circumvent the tradeoff assumed in the traditional approach.  New approaches to understanding wet traction incorporate consideration of the effect of water lubrication on the interactions between surfaces and have pointed the way to developing compounds that can provide high wet traction and low rolling resistance.<ref> "World’s greatest living rubber scientist", by David Shaw, Tire Industry Research, 2022, https://tireindustryresearch.com/2019/07/08/worlds-greatest-living-rubber-scientist/ </ref>

The most common elastomer material used today is a [[styrene]]-[[butadiene]] copolymer. It combines the properties of [[polybutadiene]], which is a highly rubbery polymer {{nowrap|([[Glass transition|''T''<sub>g</sub>]] {{=}} −100&nbsp;°C)}} having high hysteresis and thus offering good wet grip properties, with the properties of [[polystyrene]], which is a glassy polymer {{nowrap|(''T''<sub>g</sub> {{=}} 100&nbsp;°C)}} having low hysteresis and thus offering low rolling resistance in addition to [[wear]] resistance. Therefore, the ratio of the two monomers in the styrene-butadiene copolymer is considered key in determining the [[glass transition temperature]] of the material, which is correlated to its grip and resistance properties.<ref>Hao, P. T., Ismail, H., & Hashim, A. S. (2001). Study of two types of styrene butadiene rubber in tire tread compounds. ''Polymer Testing'', ''20''(5), 539–544.</ref>

Non-exhaust emissions of particulate matter, generated by the wearing down of brakes, clutches, tires, and road surfaces, as well as by the suspension of road dust, constitute a little-known but rising share of emissions from road traffic and significantly harm public health.<ref>{{Cite web|date=2020-12-07|title=Non-exhaust Particulate Emissions from Road Transport: An Ignored Environmental Policy Challenge|url= https://www.oecd.org/environment/non-exhaust-particulate-emissions-from-road-transport-4a4dc6ca-en.htm |access-date=2021-12-27 |website=oecd.org}}</ref>

== On the wheel ==
{{Main|Wheel|Bicycle wheel|Motorcycle wheel}}
[[File:Fietband lek zoeken.jpg|thumb|A [[Bicycle tire#Tubed|bicycle inner tube]] with [[valve stem]]]]
Associated components of tires include the wheel on which it is mounted, the valve stem through which air is introduced, and, for some tires, an inner tube that provides the airtight means for maintaining tire pressure.

* ''Wheel'': Pneumatic tires are mounted onto [[wheel]]s that most often have integral rims on their outer edges to hold the tire. Automotive wheels are typically made from pressed and welded steel, or a composite of lightweight metal [[alloy]]s, such as aluminum or magnesium. There are two aspects to how pneumatic tires support the rim of the wheel on which they are mounted.<ref name="Clark1">{{cite book|title=Mechanics of Pneumatic Tires |first1=Samuel K. |last1=Clark |first2=V.E. |last2=Gough |date=1981 |publisher=U.S. Department of Transportation |page=245 |quote=Consider two mechanisms of force transmission acting in parallel.}}</ref> First, the tension in the [[#Ply|cords]] pull on the [[#Bead|bead]] uniformly around the wheel, except where it is reduced above the contact patch.<ref name="Clark2">{{cite book|title=Mechanics of Pneumatic Tires |first1=Samuel K. |last1=Clark |first2=V.E. |last2=Gough |date=1981 |publisher=U.S. Department of Transportation |page=246 |quote=The only possible way in which the reaction can develop at the rim is by the changes in magnitude and direction of the membrane stresses at their points of attachment to the rim, in the region of the membrane near the point where the plate is pressed against it.}}</ref> Second, the bead transfers that net force to the rim.<ref name="Clark3">{{cite book|title=Mechanics of Pneumatic Tires |first1=Samuel K. |last1=Clark |first2=V.E. |last2=Gough |date=1981 |publisher=U.S. Department of Transportation |page=246 |quote=This force pulls the bead coil against the base of the wheel rim above the contact area, thus transmitting the upward force to the wheel.}}</ref><ref name="Clark2" /> Tires are mounted on the wheel by forcing its beads into the channel formed by the wheel's inner and outer rims.<ref>{{cite book|url= https://books.google.com/books?id=_LZMAQAAIAAJ&q=define:+wheel+rim&pg=PA579|title=American Machinist, Volume 40|date=1914-04-02|pages=597–598|access-date=2012-03-14}}</ref><ref>{{cite web|url= http://www.osha.gov/Publications/wheel/wheel-chart-booklet.pdf|title=Demounting and Mounting Procedures|year=2011|publisher=Occupational Safety and Health Administration|access-date=2012-03-14|archive-date=27 February 2012|archive-url= https://web.archive.org/web/20120227123006/http://www.osha.gov/Publications/wheel/wheel-chart-booklet.pdf|url-status=dead}}</ref>
* ''Valve stem'': Pneumatic tires receive their air through a [[valve stem]]—a tube made of metal or rubber, with a [[check valve]], typically a [[Schrader valve]] on automobiles and most bicycle tires, or a [[Presta valve]] on high-performance bicycles. They mount directly to the rim, in the case of tubeless tires, or are an integral part of the inner tube. Most modern passenger vehicles are now required to have a [[Tire-pressure monitoring system|tire pressure monitoring system]] which usually consists of a valve stem attached to an electronic module.<ref name="Erjavec-2005"/>
* ''Inner tube'': Most [[bicycle tire]]s, many [[motorcycle tire]]s, and many tires for large vehicles such as buses, heavy trucks, and tractors are designed for use with [[inner tube]]s. Inner tubes are [[torus]]-shaped balloons made from an impermeable material, such as soft, elastic synthetic rubber, to prevent air leakage. The inner tubes are inserted into the tire and inflated to retain air pressure. Large inner tubes can be reused for other purposes, such as swimming and rafting (see [[swim ring]]), [[tubing (recreation)]], [[sledding]], and [[skitching]]. Purpose-built inflatable tori are also manufactured for these uses, offering a choice of colors, fabric covering, handles, decks, and other accessories, and eliminating the protruding valve stem.

==Performance characteristics==
[[File:Tire performance envelope.svg|thumb|Tire performance envelope by Goodyear]]

The interactions of a tire with the pavement are complex. A commonly used (empirical) model of tire properties is [[Pacejka#The Pacejka "Magic Formula" tire models|Pacejka's "Magic Formula"]].<ref>{{cite news|title=Tribute: Hans Pacejka 1934-2017|url=https://www.tiretechnologyinternational.com/news/people-news/tribute-hans-pacejka-1934-2017.htmlID=87381|access-date=1 October 2017|publisher=Tire Technology International|date=September 19, 2017|archive-date=1 December 2024|archive-url=https://web.archive.org/web/20241201230755/https://www.tiretechnologyinternational.com/news/people-news/tribute-hans-pacejka-1934-2017.htmlID=87381|url-status=dead}}</ref> Some are explained below, alphabetically, by section.

=== Dynamics ===

* ''Balance'': Wheel-tire combinations require an even distribution of mass around their circumferences to maintain [[tire balance]], while turning at speed. Tires are checked at the point of manufacture for excessive static imbalance and dynamic imbalance using automatic tire balance machines. Tires are checked again in the auto assembly plant or tire retail shop after mounting the tire to the wheel. Assemblies that exhibit excessive imbalance are corrected by applying balance weights to the wheels to counteract the tire/wheel imbalance. An alternative method to tire balancing is the use of internal tire balancing agents. These agents take advantage of centrifugal force and inertia to counteract the tire imbalance.<ref>{{Cite book |last=Sabry |first=Fouad |url= https://books.google.com/books?id=KXOXEAAAQBAJ&dq=Internal+Tire+Balancing+Agents&pg=PT78 |title=Airless Tire: Reinventing the Wheel |date=2022-10-25 |publisher=One Billion Knowledgeable |language=en}}</ref> To facilitate proper balancing, most high-performance tire manufacturers place red and yellow marks on the sidewalls to enable the best possible match-mounting of the tire/wheel assembly. There are two methods of match-mounting high-performance tire-to-wheel assemblies using these red (uniformity) or yellow (weight) marks.<ref>{{cite web|url= http://www.yokohamatire.com/utmatch.asp |title=Tire Match Mounting and Balancing - Yokohama Tire |website=yokohamatire.com |access-date=2007-07-24|archive-url= https://web.archive.org/web/20070929183155/http://www.yokohamatire.com/utmatch.asp |archive-date=2007-09-29 |url-status=dead}}</ref>
* ''Centrifugal growth'': A tire rotating at higher speeds tends to develop a larger diameter, due to [[centrifugal force]]s that force the tread rubber away from the axis of rotation. This may cause [[Speedometer Error|speedometer error]]. As the tire [[diameter]] grows, the tire width decreases. This centrifugal growth can cause rubbing of the tire against the vehicle at high speeds. [[Motorcycle]] tires are often designed with reinforcements aimed at minimizing centrifugal growth.<ref name=":0A" />
* ''Pneumatic trail'': [[Pneumatic trail]] of a tire is the trail-like effect generated by compliant tires rolling on a hard surface and subject to side loads, as in a turn. More technically, it is the distance that the resultant [[Cornering force|force]] of [[Slip angle|side-slip]] occurs behind the geometric center of the [[contact patch]].<ref name="Clark">{{cite book|url= http://media.wiley.com/product_data/excerpt/19/04713546/0471354619.pdf |title=Mechanics of pneumatic tires |last=Clark |first=Samuel Kelly |publisher=U.S. Dept. of Transportation, National Highway Traffic Safety Administration, Washington, D.C. |year=1981}}</ref>
* ''Slip angle'': [[Slip angle]] or sideslip angle is the angle between a rolling wheel's actual direction of travel and the direction towards which it is pointing (i.e., the angle of the vector sum of wheel translational velocity <math>v_x</math> and sideslip velocity {{nowrap|<math>v_y</math>).}}<ref name=":0A" />
* ''Relaxation length'': [[Relaxation length]] is the delay between when a slip angle is introduced and when the cornering force reaches its steady-state value.<ref name=":0A" />
* ''Spring rate'': Vertical stiffness, or [[spring rate]], is the ratio of vertical force to vertical deflection of the tire, and it contributes to the overall suspension performance of the vehicle. In general, the spring rate increases with inflation pressure.<ref>{{cite web|url= http://www.engr.colostate.edu/pts/Job/Understanding%20Parameters%20Influencing%20Tire%20Modeling.pdf|title=Understanding Parameters Influencing Tire Modeling |first=Nicholas D. |last=Smith |date=2003 |publisher=Department of Mechanical Engineering, Colorado State University |archive-url= https://web.archive.org/web/20080920223731/http://www.engr.colostate.edu/pts/Job/Understanding%20Parameters%20Influencing%20Tire%20Modeling.pdf|archive-date=2008-09-20|url-status=dead|access-date=2014-11-23}}</ref>
* ''Stopping distance'': Performance-oriented tires have a tread pattern and rubber compounds designed to grip the road surface, and so usually have a slightly shorter stopping distance. However, specific braking tests are necessary for data beyond generalizations.<ref name=":0A" />

=== Forces ===

* ''Camber thrust'': [[Camber thrust]] and camber force are the force generated perpendicular to the direction of travel of a rolling tire due to its [[camber angle]] and finite contact patch.<ref name=":0A" />
* ''Circle of forces'': The [[circle of forces]], traction circle, friction circle, or friction ellipse is a useful way to think about the dynamic interaction between a vehicle's tire and the road surface.<ref name="Wong">{{cite book|url= https://books.google.com/books?id=LH8wd8im13AC&q=friction+ellipse|title=Theory of ground vehicles |last=Wong |first=Jo Yung |publisher=Wiley |year=2008 |isbn=978-0-470-17038-0 |edition=Second |pages=52–53}}</ref>
* ''Contact patch'': The [[contact patch]], or footprint, of the tire, is the area of the tread that is in contact with the road surface. This area transmits forces between the tire and the road via friction. The length-to-width ratio of the contact patch affects steering and cornering behavior.<ref name=":0A" />
* ''Cornering force'': [[Cornering force]] or side force is the lateral (i.e. parallel to the road surface) force produced by a vehicle tire during cornering.<ref name=":0A" />
* ''Dry traction'': Dry traction is the measure of the tire's ability to deliver traction, or grip, under dry conditions. Dry traction is a function of the tackiness of the rubber compound.<ref name=":0A" />
* ''Force variation'': The tire tread and sidewall elements undergo deformation and recovery as they enter and exit the footprint. Since the rubber is elastomeric, it is deformed during this cycle. As the rubber deforms and recovers, it imparts cyclical forces into the vehicle. These variations are collectively referred to as [[tire uniformity]]. Tire uniformity is characterized by [[Radial Force Variation|radial force variation]] (RFV), [[lateral force variation]] (LFV), and [[Tire uniformity#Tangential force variation|tangential force variation]]. Radial and lateral force variation is measured on a [[force variation machine]] at the end of the manufacturing process. Tires outside the specified limits for RFV and LFV are rejected. Geometric parameters, including radial runout, lateral runout, and sidewall bulge, are measured using a tire uniformity machine at the tire factory at the end of the manufacturing process as a quality check.<ref name=":0A" />
* ''Rolling resistance'': [[Rolling resistance]] is the resistance to rolling caused by deformation of the tire in contact with the road surface. As the tire rolls, the tread enters the contact area and is deformed flat to conform to the roadway. The energy required to make the deformation depends on the inflation pressure, rotating speed, and numerous physical properties of the tire structure, such as spring force and stiffness. Tire makers seek lower rolling resistance tire constructions to improve [[fuel economy in automobiles|fuel economy]] in cars and especially trucks, where rolling resistance accounts for a high proportion of fuel consumption. Pneumatic tires also have a much lower rolling resistance than solid tires. Because the internal air pressure acts in all directions, a pneumatic tire is able to "absorb" bumps in the road as it rolls over them without experiencing a reaction force opposite to the direction of travel, as is the case with a solid (or foam-filled) tire.<ref name=":0A" />
* ''Self aligning torque'': [[Self aligning torque|Self-aligning torque]], also known as the aligning torque, SAT or Mz, is the [[torque]] that a tire creates as it rolls along that tends to steer it, i.e. rotate it around its vertical axis.<ref name=":0A" />
* ''Wet traction'': Wet traction is the tire's [[Traction (engineering)|traction]], or grip, under wet conditions. Wet traction is improved by the tread design's ability to channel water out of the tire footprint and reduce [[Aquaplaning|hydroplaning]]. However, tires with a circular cross-section, such as those found on racing bicycles, when properly inflated have a sufficiently small footprint to not be susceptible to hydroplaning. For such tires, it is observed that fully slick tires will give superior traction on both wet and dry pavement.<ref>{{cite web|url= http://www.sheldonbrown.com/tires.html |title=Sheldon Brown on tires |last=Brown |first=Sheldon |access-date=2008-07-01}}</ref>

=== Load ===
* ''Load sensitivity'': [[Tire load sensitivity|Load sensitivity]] is the behavior of tires under load. Conventional pneumatic tires do not behave as [[Friction#Laws of dry friction|classical friction]] theory would suggest. Namely, the load sensitivity of most real tires in their typical operating range is such that the coefficient of friction decreases as the vertical load, Fz, increases.<ref name=":0A" />
* {{anchor|TKPH}}''Work load'': The work load of a tire is monitored so that it is not put under undue stress, which may lead to its premature failure.<ref>{{cite web|url= http://www.sae.org/technical/standards/J1098_199505 |title=Ton Kilometer Per Hour (TKPH) J1098_199505 |website=sae.org |date=1 June 1995|access-date=31 January 2024}}</ref> Work load is measured in ''Ton Kilometer Per Hour'' (TKPH). The measurement's appellation and units are the same. The recent shortage and increasing cost of tires for [[Construction & Mining Trucks#Off-road dump truck|heavy equipment]] has made TKPH an important parameter in tire selection and equipment maintenance for the mining industry. For this reason, [[:Category:Tire manufacturers|manufacturers of tires]] for large earth-moving and mining vehicles assign TKPH ratings to their tires based on their size, construction, tread type, and rubber compound.<ref>{{cite web|url= http://www.firestone.co.za/content.asp?id=186|title=How to use TKPH |website=firestone.co.za |archive-url= https://web.archive.org/web/20060927202203/http://www.firestone.co.za/content.asp?id=186 |archive-date=September 27, 2006 |access-date=October 7, 2007}}</ref><ref>{{cite web|url= http://www.goodyear.com/media/pr/pr_2000/22169oh.html|title=New temperature prediction model improves on current TKPH formula |website=goodyear.com |archive-url= https://web.archive.org/web/20061106074110/http://www.goodyear.com/media/pr/pr_2000/22169oh.html |archive-date=November 6, 2006 |access-date=October 7, 2007}}</ref> The rating is based on the weight and speed that the tire can handle without overheating and causing it to deteriorate prematurely. The equivalent measure used in the United States is ''Ton Mile Per Hour'' (TMPH).

=== Wear ===
{{see also|Rubber pollution|Road wear}}Tire wear is a major source of [[rubber pollution]]. A concern hereby is that vehicle tire wear pollution is unregulated, unlike exhaust emissions.<ref>{{Cite journal|last1=Tamis|first1=Jacqueline E.|last2=Koelmans|first2=Albert A.|last3=Dröge|first3=Rianne|last4=Kaag|first4=Nicolaas H. B. M.|last5=Keur|first5=Marinus C.|last6=Tromp|first6=Peter C.|last7=Jongbloed|first7=Ruud H.|date=2021-07-02|title=Environmental risks of car tire microplastic particles and other road runoff pollutants|journal=Microplastics and Nanoplastics|volume=1|issue=1|pages=10|doi=10.1186/s43591-021-00008-w|s2cid=237303583|issn=2662-4966|doi-access=free}}</ref>

[[File:Tire Severe Under Inflation Wear.jpg|thumb|right|Tire showing uneven tread wear to the point of exposing the casing]]

;Tread wear: This occurs through normal contact with roads or terrain; there are several types of abnormal tread wear. Poor [[wheel alignment]] can cause excessive wear of the innermost or outermost ribs. Gravel roads, rocky terrain, and other rough terrain cause accelerated wear. Over-inflation above the sidewall maximum can cause excessive wear to the center of the tread. Modern tires have steel belts built in to prevent this. Under-inflation causes excessive wear to the outer ribs. Unbalanced wheels can cause uneven tire wear, as the rotation may not be perfectly circular. Tire manufacturers and car companies have mutually established standards for tread wear testing that include measurement parameters for tread loss profile, lug count, and heel-toe wear.<ref name=":0A" />

[[File:Tread Wear Indicators of Studless Tire.jpg|thumb|right|Wear bar and tread wear indicator on the snow tire tread]]

;Tread wear indicators ('''T.W.I.'''): Raised bars in the tread channels, which indicate that the tread is becoming worn and therefore unsafe. Indicators have been required on all new tires since 1968 in the US.<ref>{{cite journal |title=Tire |journal=The Rubber Age |date=1968 |volume=100 |issue=1 |page=102 |url= https://books.google.com/books?id=RSZWAAAAYAAJ&q=Tread+wear+indicators |publisher=Palmerton Publishing |quote=One requirement provides that ... all new tires shall be equipped with a tread-wear indicator that will show at a glance when the tread depth has been worn to 1/16 of an inch. |access-date=7 August 2019}}</ref> In many countries the Highway Code forbids driving on public roads when the contact surface is flush with any of these bars - this is often defined when the groove depth is approximately 1.5 or 1.6&nbsp;mm (2/32 inch). TWI can also be used to refer to small arrows or icons on the tire sidewall, indicating the location of the raised wear bars.
;Damage by aging: Tire aging or "thermo-oxidative degradation" can be caused by time, ambient and operating temperatures, partial pressure of O2 in a tire, flex fatigue, or construction and compounding characteristics. For example, prolonged UV exposure leads to rubber's chemicals warping, potentially causing dry rot. Various storage methods may slow the aging process, but will not eliminate tire degradation.<ref>{{cite web |last=Kane |first=Sean |title=Tire Aging and Service Life NTSB Tire Safety Symposium |url= https://www.ntsb.gov/news/events/Documents/2014_Tire_Safety_SYM_Panel_4b_Kane.pdf |publisher=NTSB |date=10 December 2014 |access-date=7 August 2019}}</ref>

==Sizes, codes, standards, and regulatory agencies==
[[File:Tire_code_-_en.svg|alt=|thumb|upright=1.35|Tire identification diagram with [[tire code]]s]]
{{Further|Tire code}}
Automotive tires have a variety of identifying markings molded onto the sidewall as a [[tire code]]. They denote size, rating, and other information pertinent to that individual tire.

=== Americas ===
The [[National Highway and Traffic Safety Administration]] (NHTSA) is a U.S. government body within the [[United States Department of Transportation|Department of Transportation]] (DOT) tasked with regulating automotive safety in the United States.<ref name="DoT">{{Cite web |title=49 CFR § 574.5 - Tire identification requirements. |url= https://www.law.cornell.edu/cfr/text/49/574.5 |access-date=2024-01-18 |website=LII / Legal Information Institute |language=en}}</ref> NHTSA established the Uniform Tire Quality Grading System ([[UTQG]]), is a system for comparing the performance of tires according to the Code of Federal Regulations 49 CFR 575.104; it requires labeling of tires for tread wear, traction, and temperature. The DOT Code is an [[alphanumeric]] character sequence molded into the sidewall of the tire and allows the identification of the tire and its age. The code is mandated by the [[United States Department of Transportation|U.S. Department of Transportation]]<ref name="DoT" /> but is used worldwide.<ref>{{Cite web|url= https://www.rubbernews.com/article/20160309/NEWS/160309961/dept-of-transportation-issues-new-dot-codes |title=Dept. of Transportation issues new DOT codes|date=2016-03-09|access-date=2018-12-29|archive-url= https://web.archive.org/web/20190507124526/https://www.rubbernews.com/article/20160309/NEWS/160309961/dept-of-transportation-issues-new-dot-codes|archive-date=2019-05-07 |url-status=dead}}</ref> The DOT Code is also useful in identifying tires subject to [[product recall]]<ref>{{cite web|url= https://www.goodyear.com/en-US/tires/recall |title=Goodyear Tire Recall |website=goodyear.com}}</ref> or at end of life due to age. The ''Tire and Rim Association'' (T&RA) is a voluntary U.S. standards organization that promotes the interchangeability of tires, rims, and allied parts. Of particular interest, they publish key tire dimensions, rim contour dimensions, tire valve dimension standards, and load/inflation standards.

The [[National Institute of Metrology Standardization and Industrial Quality]] (INMETRO) is the [[Brazil]]ian federal body responsible for automotive wheel and tire certification.<ref>{{cite book|url= https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication941.pdf |title=Free Trade Area of the Americas (FTAA) Conformity Assessment Infrastructure |last=Londono |first=Carmina |date=July 1999 |publisher=National Institute of Standards and Technology |location=Gaithersburg, MD}}</ref>

===Europe===
The [[European Tyre and Rim Technical Organisation]] (ETRTO) is the European standards organization "to establish engineering dimensions, load/pressure characteristics and operating guidelines".<ref>{{cite book| title=ETRTO Standards Manual 2007 | year=2007| publisher=ETRTO |location=Bruxelles, Belgium | pages=I }}</ref> All tires sold for road use in Europe after July 1997 must carry an E-mark. The mark itself is either an upper case "E" or lower case "e"&nbsp;– followed by a number in a circle or rectangle, followed by a further number. An (upper case) "E" indicates that the tire is certified to comply with the dimensional, performance, and marking requirements of ECE regulation 30. A (lowercase) "e" indicates that the tire is certified to comply with the dimensional, performance, and marking requirements of Directive 92/23/EEC. The number in the circle or rectangle denotes the country code of the government that granted the type approval. The last number outside the circle or rectangle is the number of the type approval certificate issued for that particular tire size and type.<ref>{{Cite book|url= https://books.google.com/books?id=IbW8BAAAQBAJ&q=european+tire+e+mark&pg=PA8 |title=Vehicle Dynamics: Theory and Application |last=Jazar |first=Reza N. |date=2013-11-19 |publisher=Springer Science & Business Media |isbn=9781461485445}}</ref>

The [[Rubber Manufacturers Association#British Rubber Manufacturers Association|British Rubber Manufacturers Association]] (BRMA) recommended practice, issued June 2001, states, "BRMA members strongly recommend that unused tires should not be put into service if they are over six years old and that all tires should be replaced ten years from the date of their manufacture."<ref>{{Cite web|url= http://www.thechronicleherald.ca/wheels/have-your-tires-reached-their-expiration-date-255224/ |title=Have your tires reached their expiration date? |last=Russell|first=Richard |date=October 31, 2018 |work=The Chronicle Herald |access-date=2019-05-06}}</ref>

===Asia===
The Japanese Automobile Tire Manufacturers Association (JATMA) is the Japanese standards organization for tires, rims, and valves.<ref>{{Cite book|title=JATMA year book: tyre standards |date=2019 |publisher=The Japan Automobile Tyre Manufacturers Association |isbn=9784909716026 |location=Tokyo |oclc=1086187385}}</ref> It performs similar functions as the T&RA and ETRTO.

The China Compulsory Certification (CCC) is a mandatory certification system concerning product safety in China that went into effect in August 2002. The CCC certification system is operated by the State General Administration for Quality Supervision and Inspection and Quarantine of the People's Republic of China (AQSIQ) and the Certification and Accreditation Administration of the People's Republic of China (CNCA).<ref>{{cite book|title=A brief guide to CCC: China Compulsory Certification |last=Busch |first=Julian |date=2013 |publisher=CreateSpace Independent Publ. |isbn=9781484115534 |oclc=959836294}}</ref>

== Maintenance ==
[[File:Niger, Kodo (8), tire repair shop.jpg|thumb|right|A tire repair shop in Niger]]

To maintain tire health, several actions are appropriate, tire rotation, wheel alignment, and, sometimes, retreading the tire.

* ''Rotation'': Tires may exhibit irregular wear patterns once installed on a vehicle and partially worn. [[Front-wheel drive]] vehicles tend to wear the front tires at a greater rate compared to the rear tires. Tire rotation is moving the tires to different car positions, such as front-to-rear, in order to even out the wear, with the objective of extending the life of the tire.<ref name="Gilles">{{cite book|url= https://books.google.com/books?id=mNIhYSCBfmUC&q=m%2Bs+tire+rating&pg=PA271|title=Automotive Chassis: Brakes, Suspension, and Steering |last=Gilles|first=Tim |date=2005 |publisher=Thompson Delmar Learning |isbn=9781401856304 |location=Santa Barbara |page=551}}</ref>
* ''Alignment'': [[Wheel alignment]] helps prevent wear due to rotation in a direction other than the path of the vehicle. When mounted on the vehicle, the wheel and tire may not be perfectly aligned to the direction of travel, and therefore may exhibit irregular wear. If the discrepancy in alignment is large, then the irregular wear will become substantial if left uncorrected. Wheel alignment is the procedure for checking and correcting this condition through adjustment of [[Camber angle|camber]], [[Caster angle|caster]], and [[Toe (automotive)|toe]] angles. The adjustment of the angles should be done as per the OEM specifications.<ref>{{cite book |last1=Kershaw |first1=John F. |title=Automotive steering and suspension |date=2018 |first2=Kirk |last2=VanGelder |isbn=9781284102093 |location=Burlington, MA |pages=460–494 |oclc=1002887535}}</ref>

=== Inflation ===
[[File:Rolling resistance vs inflation -- NHTSA The Pneumatic Tire.png|thumb|upright=1.35|Rolling resistance as a function of tire inflation]]

Inflation is key to proper wear and rolling resistance of pneumatic tires. Many vehicles have monitoring systems to assure proper inflation. Most passenger cars are advised to maintain a tire pressure within the range of {{convert|32|to|35|psi|kPa|lk=on|order=flip}} when the tires are not warmed by driving.<ref>{{cite web |last=Bruzek |first=Joe |date=2018-05-15 |title=How Do I Find the Correct Tire Pressure for My Car? |url= https://www.cars.com/articles/how-do-i-find-the-correct-tire-pressure-for-my-car-1420676891878/ |accessdate=2023-03-06 |website=Cars.com}}</ref><ref>{{Cite web |title=What is the ideal tyre pressure? |url= https://www.ozzytyres.com.au/news/what-is-the-ideal-tyre-pressure |access-date=2024-01-18 |website=carsonline|date=4 October 2023 }}</ref>

* ''Specification—'' Vehicle manufacturers provide tire specifications, including a recommended [[cold inflation pressure]], to ensure safe operation within the designated load rating and vehicle loading capacity. While many tires feature a maximum pressure rating stamped on them, passenger vehicles and light trucks typically include inflation guidance on a decal located just inside the driver's door and in the vehicle owner's handbook.<ref>{{cite web|last=Brand |first=Paul|date=March 13, 2015|title=Which tire pressure rating should motorists heed? |url= https://www.startribune.com/which-tire-pressure-rating-should-motorists-heed/296203951/ |access-date=2021-07-19 |work=Star Tribune}}</ref>
* ''Ground contact'': The tire contact patch is readily changed by both over- and underinflation. Overinflation may increase the wear on the center contact patch, and underinflation will cause a concave tread, resulting in less center contact, though the overall contact patch will still be larger.<ref>{{cite web|url= http://www.barrystiretech.com/airortire.html |title=Air or Tire|access-date=2015-04-15}}</ref> Most modern tires will wear evenly at high tire pressures, but will degrade prematurely if underinflated. Increased tire pressure may decrease rolling resistance, and may also result in shorter stopping distances<ref>{{cite web|url= http://www.nhtsa.dot.gov/Cars/rules/rulings/TirePresFinal/FEA/TPMS3.html |title=FEA Chapter III: Tire pressure survey and test results|access-date=2009-01-16|archive-date=6 October 2008|archive-url= https://web.archive.org/web/20081006005308/http://www.nhtsa.dot.gov/cars/rules/rulings/TirePresFinal/FEA/TPMS3.html|url-status=dead}}</ref> If tire pressure is too low, the tire contact patch is greatly increased. This increases rolling resistance, tire flexing, and friction between the road and the tire. Under-inflation can lead to tire overheating, premature tread wear, and tread separation in severe cases.<ref>{{cite web|url= http://www.nhtsa.dot.gov/Cars/rules/rulings/TirePresFinal/FEA/TPMS3.html|title=NHTSA test|access-date=2009-01-16 |archive-date=6 October 2008 |archive-url= https://web.archive.org/web/20081006005308/http://www.nhtsa.dot.gov/cars/rules/rulings/TirePresFinal/FEA/TPMS3.html|url-status=dead}}</ref>
* ''Monitoring'': [[Tire pressure monitoring system]]s (TPMS) are electronic systems that monitor the tire pressures on individual wheels on a vehicle and alert the driver when the pressure goes below a warning limit. There are several types of designs to monitor tire pressure. Some actually measure the air pressure, and some make indirect measurements, such as gauging when the relative size of the tire changes due to lower air pressure.

== Hazards ==
[[File:Tire_bubble.jpg#|thumb|Tire bubble|upright]]
[[File:Weather-cracked Tire.JPG|thumb|Tire showing weather-cracking over long-term exposure to the weather]]
[[File:Flat tire 2.jpg|thumb|A flat tire on a passenger car]]
Tire hazards may occur from failure of the tire, itself, or from loss of traction on the surface over which it is rolling. Structural failures of a tire can result in [[flat tire]]s or more dangerous [[Blowout (tire)|blowouts.]] Some of these failures can be caused by manufacture error and may lead to recalls, such as the widespread Firestone tire failures on Ford vehicles that lead to the [[Firestone and Ford tire controversy]] in the 1990s.

=== Tire failure ===
Tires may fail for any of a variety of reasons, including:<ref>{{cite book|title=Tire forensic investigation : analyzing tire failure |last=Giapponi |first=Thomas R. |date=2008 |publisher=SAE International |isbn=9780768019551 |location=Warrendale, Pa. |oclc=213080702}}</ref>

{{Anchor|Belt separation}}
* ''Belt separation'' which may be belt-to-belt, tread and belt, or separation of the edge of the belt. Belt-to-belt separation may occur having the tire deflect too much, from high pavement temperatures, road hazard impacts, or other causes that have to do with maintenance and storage.
{{Anchor|Non-belt separation|Non-belt separations}}
* ''Non-belt separations'' include those at the tire tread, in the bead area, in the lower sidewall, between reinforcing plies, and of the reinforcing steel or fabric materials.
* Other types of failure include run-flat damage, chemical degradation, cracking, indentations and bulges.

===Vehicle operation failures===

* ''Melting rubber'': As tire rubber compounds heat, owing to the friction of stopping, cornering, or accelerating, they may begin to melt, lubricate the tire-road contact area, and become deposited on the pavement. This effect is stronger with increased ambient temperature.<ref name=":0A" />
* ''Hydroplaning'': Motor vehicles or aircraft tires passing over a wet pavement may lose contact with sufficient speed or water depth for a given tread design. In this case, the tire contact area is riding on a film of water and loses the friction needed for braking or cornering and begins to ''[[Aquaplaning|hydroplane]]'' (or ''aquaplane''). Hydroplaning may occur as ''dynamic hydroplaning'' where standing water is present with a depth of at least {{Convert|3|mm|in}} above the texture of the pavement and speed is sustained above a threshold level. It may also occur as ''viscous hydroplaning'' whereby tire rubber melts for a brief interval and causes slippage. This may leave deposits of rubber on a [[runway]] as airplanes land.<ref>{{cite book|url= https://books.google.com/books?id=lrRCWz3f_78C&q=aquaplaning+vs+hydroplaning&pg=PA89|title=Aircraft Performance Theory for Pilots |last=Swatton |first=Peter J. |date=2008-04-30 |publisher=John Wiley & Sons |isbn=9780470693056 |location=New York |pages=89–91}}</ref> Dynamic hydroplaning causes decreased friction and contact with increased tire speed.<ref>{{cite book|url= https://books.google.com/books?id=aLgNET9YkS0C&q=aquaplaning+vs+hydroplaning&pg=PA287 |title=Advanced Vehicle Technology |last=Heisler |first=Heinz |date=2002-07-17 |publisher=Elsevier |isbn=9780080493442}}</ref>
* ''Snow'': The degree to which a tire can maintain traction in snow depends on its ability to compact snow, which material then develops strength against slippage along a shear plane parallel to the contact area of the tire on the ground.<ref>{{Cite book|url= https://books.google.com/books?id=U_Y5AQAAMAAJ&q=traction+in+mud|title=Driving Traction on Ice with All-season and Mud-and-snow Radial Tires |last=Blaisdell|first=George L.|date=1983|publisher=US Army Corps of Engineers, Cold Regions Research & Engineering Laboratory|language=en}}</ref> At the same time, the bottom of the tire treads compress the snow on which they are bearing, also creating friction. The process of compacting snow within the treads requires it to be expelled in time for the tread to compact snow anew on the next rotation. The compaction/contact process works both in the direction of travel for propulsion and braking, but also laterally for cornering.<ref name="Hays2"/>
* ''Ice'': Ice is typically close to its melting point when a tire travels over it. This, combined with a smooth texture, promotes a low coefficient of friction and reduced traction during braking, cornering or acceleration.<ref name=":0A" />
* ''Soft ground'': Soil can become lubricated with water, which reduces its ability to maintain shear strength when a tire tries to apply force in acceleration, braking, or cornering. Dry sand also has low shear strength, owing to poor cohesiveness among sand particles.<ref>{{cite book|url= https://books.google.com/books?id=tyje5iXkGmUC&q=traction+in+mud&pg=PA74 |title=Four-Wheeler's Bible |last=Allen |first=Jim |date=2009 |publisher=MotorBooks International |isbn=9781616730888}}</ref>

== Health impacts ==
{{Further|Rubber pollution}}
Tires contain a number of trace toxic chemicals including heavy metals and chemical agents used to increase the durability of the tires.<ref name="Tan-2023" /> These typically include [[polycyclic aromatic hydrocarbon]], [[benzothiazoles]], [[isoprene]] and heavy metals such as [[zinc]] and [[lead]].<ref name="Tan-2023" />

As tires are used for vehicle operations, the natural wear of the tire leaves microfine particles equivalent to [[PM0.1]], [[PM2.5]], and [[PM10]] as tire residue.<ref name="Tan-2023" /> This residue accumulates near roadways and vehicle use areas, but also will travel into the environment through [[surface runoff]].<ref name="Tan-2023" /> Both humans and animals are exposed to these chemicals at the sites of accumulation (i.e. walking on the road surface) and through [[bioaccumulation]] in natural environments and foodchains.<ref name="Tan-2023" /> A 2023 literature review from Imperial College London, warned of both the toxic chemicals and microplastics produced from tire wear as having potential widespread serious environmental and health consequences.<ref name="Tan-2023" />

Moreover, burning of tires releases these chemicals as air pollutants that can harm first responders and leaves toxic residues that endanger local communities.<ref>{{Cite web |title=Tire Fires {{!}} Scrap Tires {{!}} US EPA |url= https://archive.epa.gov/epawaste/conserve/materials/tires/web/html/fires.html |access-date=2023-02-26 |website=archive.epa.gov |language=en}}</ref>

== End of use ==
{{main|Tire recycling}}
[[File:Tires recycled into water tanks on roof. Cherchen, Xinjiang.jpg|thumb|Tires recycled into water tanks on the roof in [[Cherchen]], Xinjiang]]

Once tires are discarded, they are considered scrap tires. Scrap tires are often re-used for things from bumper car barriers to weights to hold down tarps. Tires are not desired at [[landfills]], due to their large volumes and 75% void space, which quickly consumes valuable space. Rubber tires are likely to contain some traces of [[Heavy metal (chemistry)|heavy metal]]s or other serious [[pollutant]]s, but these are tightly bonded within the actual rubber compound so they are unlikely to be hazardous unless the tire structure is seriously damaged by fire or strong chemicals.<ref>Liu, H., Mead, J., Stacer, R. Chelsea Center For Recycling And Economic Development. (1998). Environmental Impacts Of Recycling Rubber In Light Fill Applications: Summary & Evaluation Of Existing Literature University of Massachusetts</ref> Some facilities are permitted to recycle scrap tires by chipping and processing them into new products or selling the material to licensed power plants for fuel. Some tires may also be retreaded for re-use.

===Environmental issues===
[[File:Tyre fire.jpg|thumb|Toxic fumes emerging from a fire at a tire dump.|upright]]
Americans generate about 285 million scrap tires per year.<ref>{{cite web|url= http://www.epa.gov/waste/conserve/materials/tires/tdf.htm |archive-url= https://web.archive.org/web/20091021042308/http://www.epa.gov/waste/conserve/materials/tires/tdf.htm |url-status= dead |archive-date= 21 October 2009 |title=Tire-Derived Fuel |publisher=U.S. Environmental Protection Agency |access-date=2011-12-29}}</ref> Many states regulate the number of scrap tires that can be held at any site out of concern with dumping, fire hazards, and mosquitoes. In the past, millions of tires were simply discarded into open fields. Outdoor tire heaps create breeding grounds for mosquitoes, which are a nuisance and may spread disease, since the tires often hold water inside and remain warm enough for mosquito breeding. It also creates a fire hazard. Tires very seldom catch fire inadvertently, requiring a temperature of {{convert|400|C|F}} to [[combustion|combust]],<ref>{{cite web |title=Are Tires Flammable? You May Be Surprised… |website=Firefighter Insider |date=13 April 2021 |url=https://firefighterinsider.com/tires-flammable/ |access-date=29 June 2025}}</ref> but once burning are hard to extinguish, for a large tire pile has ample fuel and water used to douse fires does not adequately penetrate or cool them. Some [[tire fire]]s have burned for months, sometimes [[liquefaction|liquefying]] and releasing hydrocarbons and other contaminants to the ground and even groundwater, and black smoke, an air pollutant that is a hazard to downwind properties, to the air.

The use of scrap tire chips for landscaping has become controversial because of the leaching of metals and other contaminants from the tire pieces. Zinc is concentrated (up to 2% by weight) to levels high enough to be highly toxic to aquatic life and plants.<ref>{{cite web|url= http://www.ardeacon.com/pdf/Assessment_Environmental_Toxicity_Report.pdf |title=An Assessment of Environmental Toxicity and Potential Contamination from Artificial Turf using Shredded or Crumb Rubber |last=Sullivan |first=Joseph P. |year=2006 |access-date=2009-06-01 |archive-date=16 August 2009 |archive-url= https://web.archive.org/web/20090816063708/http://www.ardeacon.com/pdf/Assessment_Environmental_Toxicity_Report.pdf|url-status=dead}}</ref> Of particular concern is evidence that some of the compounds that leach from tires into the water contain hormone disruptors and cause liver lesions.<ref>{{cite web|url= https://puyallup.wsu.edu/wp-content/uploads/sites/403/2015/03/rubber-mulch.pdf |title=The Myth of Rubberized Landscapes |last=Chalker-Scott |first=Linda |archive-url= https://web.archive.org/web/20091007125638/http://www.puyallup.wsu.edu/~Linda%20Chalker-Scott/Horticultural%20Myths_files/Myths/Rubber%20mulch.pdf |archive-date=2009-10-07 |url-status=live |access-date=2009-06-01}}</ref>

Tires are a major source of [[Microplastics|microplastic]] pollution, found in a 2020 study to contribute 78% of the total mass of microplastics found in the ocean.<ref>{{cite web|url= https://www.sciencenews.org/article/car-tires-and-brake-pads-produce-harmful-microplastics |title=Car tires and brake pads produce harmful microplastics |date=2018-11-12 |work=Science News |access-date=2019-10-06}}</ref><ref>{{Cite news |last=LaBrecque |first=Sarah |date=2023-07-17 |title=Rising microplastics in seas puts pressure on tyre industry |url=https://www.reuters.com/sustainability/land-use-biodiversity/rising-microplastics-seas-puts-pressure-tyre-industry-2023-07-17/ |access-date=2025-01-15 |work=[[Reuters]]}}</ref> The commonly used compound [[6PPD|6PPD-quinone]], found entering stormwater runoff via tire-wear particles, has been identified as toxic to coho salmon, brook trout, and rainbow trout.<ref>{{Cite journal |last1=Tian |first1=Zhenyu |last2=Zhao |first2=Haoqi |last3=Peter |first3=Katherine T. |last4=Gonzalez |first4=Melissa |last5=Wetzel |first5=Jill |last6=Wu |first6=Christopher |last7=Hu |first7=Ximin |last8=Prat |first8=Jasmine |last9=Mudrock |first9=Emma |last10=Hettinger |first10=Rachel |last11=Cortina |first11=Allan E. |last12=Biswas |first12=Rajshree Ghosh |last13=Kock |first13=Flávio Vinicius Crizóstomo |last14=Soong |first14=Ronald |last15=Jenne |first15=Amy |date=2021-01-08 |title=A ubiquitous tire rubber–derived chemical induces acute mortality in coho salmon |url=https://www.science.org/doi/10.1126/science.abd6951 |journal=Science |volume=371 |issue=6525 |pages=185–189 |doi=10.1126/science.abd6951|pmid=33273063 |bibcode=2021Sci...371..185T |url-access=subscription }}</ref>

=== Retreading ===
{{Main|retread}}
Tires that are fully worn can be [[retread]]ed, re-manufactured to replace the worn tread.<ref>{{cite book|url= https://books.google.com/books?id=p5PmOvoU2zAC&q=%C2%A0Tires+recycled+into+new+tires+through+retreading&pg=PA169|title=Recycling, International Trade and the Environment |last=van Beukering|first=P.J. |date=2001-02-28 |publisher=Springer Science & Business Media |isbn=9780792368984}}</ref> This is known as retreading or recapping, a process of buffing away the worn tread and applying a new tread.<ref>{{cite web|url= http://www.besttiresguide.com/retread-tires |title=What are Retread Tires? |publisher=Best Tires Guide |archive-url= https://web.archive.org/web/20140717064038/http://www.besttiresguide.com/retread-tires/ |archive-date=2014-07-17|url-status=dead|access-date=2014-04-06}}</ref> There are two main processes used for retreading tires, called mold-cure and pre-cure methods. Both processes start with the inspection of the tire, followed by non-destructive inspection method such as [[shearography]]<ref>MK Meybodi, I Dobrev, P Klausmeyer, EJ Harrington, C Furlong, "[http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1359093 Investigation of thermomechanical effects of lighting conditions on canvas paintings by laser shearography]", SPIE Optical Engineering+ Applications, 2012</ref> to locate non-visible damage and embedded [[Road debris|debris]] and nails. Some casings are repaired and some are discarded. Tires can be retreaded multiple times if the casing is in usable condition. Tires used for short delivery vehicles are retreaded more than long haul tires over the life of the tire body. Casings fit for retreading have the old tread buffed away to prepare for retreading.<ref name="Bodziak">{{cite book|url= https://books.google.com/books?id=yRsHlttaMrMC&pg=PA90 |title=Tire Tread and Tire Track Evidence: Recovery and Forensic Examination Practical Aspects of Criminal & Forensic Investigations |last=Bodziak |first=William |publisher=CRC Press |year=2008 |isbn=9781420006827|pages=90}}</ref>

During the retreading process, retread technicians must ensure the casing is in the best condition possible to minimize the possibility of a casing failure. Casings with problems such as capped tread, tread separation, irreparable cuts, corroded belts or sidewall damage, or any run-flat or skidded tires, will be rejected. The mold cure method involves the application of raw rubber on the previously buffed and prepared casing, which is later cured in matrices. During the curing period, vulcanization takes place, and the raw rubber bonds to the casing, taking the tread shape of the matrix. On the other hand, the pre-cure method involves the application of a ready-made tread band on the buffed and prepared casing, which later is cured in an autoclave so that vulcanization can occur.<ref name="Bodziak" />

=== Recycling ===
Tires can be recycled into, among other things, the hot melt [[Bitumen|asphalt]], typically as [[crumb rubber]] modifier—recycled asphalt pavement (CRM—RAP),<ref>Kandhal PS. (1992). [http://ntl.bts.gov/lib/6000/6400/6407/rep92-6.pdf Waste Materials in Hot Mix Asphalt - an overview] {{Webarchive|url= https://web.archive.org/web/20090513181152/http://ntl.bts.gov/lib/6000/6400/6407/rep92-6.pdf |date=13 May 2009 }}. National Center for Asphalt Technology.</ref><ref>T. E. Baker (2003). [http://www.wsdot.wa.gov/biz/mats/Draft%20Final%20Report%20Version%205.pdf Evaluation of the Use of Scrap Tires in Transportation Related Applications in the State of Washington] {{webarchive|url= https://web.archive.org/web/20110610051824/http://www.wsdot.wa.gov/biz/mats/Draft%20Final%20Report%20Version%205.pdf |date=2011-06-10 }}</ref> and as an aggregate in [[portland cement]] [[concrete]].<ref>M Nehdi, A Khan, (2001). [http://www.bvsde.paho.org/bvsacd/cd24/cementi.pdf Cementitious Composites Containing Recycled Tire Rubber: An Overview of Engineering Properties and Potential Applications] {{Webarchive|url= https://web.archive.org/web/20110724084425/http://www.bvsde.paho.org/bvsacd/cd24/cementi.pdf |date=24 July 2011 }}. ''Cement, Concrete, and Aggregates''.</ref> Shredded tires can create [[rubber mulch]] on playgrounds to diminish fall injuries.<ref>{{Cite book|url= https://archive.org/details/askgardendoctor10000unse|title=Ask the garden doctor : 1,200 cures for common garden problems |date=2010 |publisher=Wiley |others=Schrock, Denny.|isbn=9780470878422|location=Hoboken, N.J.|oclc=656770746}}</ref> There are some "green" buildings that are being made both private and public buildings that are made from old tires.<ref>{{Cite journal|last=Bignozzi|first=Maria Chiara |date=2011 |title=Sustainable Cements for Green Buildings Construction |journal=Procedia Engineering |volume=21 |pages=915–921 |doi=10.1016/j.proeng.2011.11.2094|doi-access=free}}</ref>

The [[tire pyrolysis]] method for recycling used tires is a technique that heats whole or shredded tires in a reactor vessel containing an [[Hypoxia (environmental)|oxygen-free]] atmosphere and a heat source. In the reactor, the [[rubber]] is softened after which the rubber polymers continuously break down into smaller molecules.

=== Other uses ===
Other downstream uses have been developed for worn-out tires, including:

* ''Building elements'': Tires filled with earth have been used as garden containers<ref>{{cite web|url= http://www.backwoodshome.com/articles2/sanders98.html |title=A new use for old tires: A garden using tires |website=backwoodshome.com |date=22 March 2006}}</ref> house foundations,<ref>{{cite web |date=2010-12-30 |title='Earthships' in the Desert Save Owners Cash |url= https://abcnews.go.com/Technology/earthship-homes-desert-save-owners-cash/story?id=12501438 |work=ABC News}}</ref> bullet-proof walls<ref>{{cite web |title=Five Uses For Old Tires Around Your Retreat |url= http://www.thesurvivalistblog.net/tires/ |url-status=usurped |archive-url= https://web.archive.org/web/20130218202937/http://www.thesurvivalistblog.net/tires/ |archive-date=2013-02-18 |access-date=8 July 2013 |work=The Survivalist Blog}}</ref> and to prevent soil erosion in flood plains.<ref>{{cite news|url= https://www.latimes.com/archives/la-xpm-1996-07-28-mn-28794-story.html |title=Tire Dam to Tread on Erosion Problem |first=Arthur H.|last=Rotstein |date=28 July 1996 |newspaper=LA Times}}</ref> [[Tire wall]]s are a common feature of [[motor racing circuit]]s for safety.
* ''Recreational equipment'': Used tires are employed as exercise equipment for athletic programs such as [[American football]].<ref>{{cite web|url= http://football.about.com/od/Football-Conditioning/a/Football-Tire-Drills.htm |website=about.com |title=No Frills Football Conditioning|first=Sean|last=McCormick|url-status=dead |archive-url= https://web.archive.org/web/20130403200128/http://football.about.com/od/Football-Conditioning/a/Football-Tire-Drills.htm |archive-date=2013-04-03}}</ref> One classic conditioning drill that hones players' speed and agility is the "Tire Run" where tires are laid out side by side, with each tire on the left a few inches ahead of the tire on the right in a zigzag pattern. Athletes then run through the tire pattern by stepping in the center of each tire. The drill forces athletes to lift their feet above the ground higher than normal to avoid tripping on the tires.<ref>{{cite web|url= http://www.livestrong.com/article/317036-football-tire-drills/#ixzz2PFqqQ6Wa |publisher=LiveStrong |title=Football Tire Drills |access-date=April 1, 2013 |date=November 24, 2010 |first=Jae |last=Ireland}}</ref> Old tires are sometimes converted into a [[Swing (seat)|swing]] for play.<ref>{{cite magazine |last=Sawyers |first=Harry |date= |title=One Day Project: Kid's Backyard Tire Swing |url= http://www.popularmechanics.com/home/how-to-plans/backyard-tire-swing-project |access-date=2024-01-18 |magazine=Popular Mechanics}}</ref>
* ''Burning tires as protest'': [[Protest]]ors, worldwide, have burned tires to create black smoke.<ref>{{Cite web |title=Yemen: Protesters burn tires and obstruct roads in multiple parts of Aden Governorate late Aug. 22 to denounce power outages |url= https://crisis24.garda.com/alerts/2023/08/yemen-protesters-burn-tires-and-obstruct-roads-in-multiple-parts-of-aden-governorate-late-aug-22-to-denounce-power-outages |access-date=2024-01-21 |website=Yemen: Protesters burn tires and obstruct roads in multiple parts of Aden Governorate late Aug. 22 to denounce power outages {{!}} Crisis24 |language=en}}</ref><ref>{{cite book |last=S |first=Roger Powers |url= https://books.google.com/books?id=xmlWr4aAt4EC&q=tires |title=Protest, Power, and Change: An Encyclopedia of Nonviolent Action from ACT-UP to Women's Suffrage |date=1997-01-01 |publisher=Routledge |isbn=978-1-136-76482-0 |language=en}}</ref>
* [[Necklacing]] is the use of tires to kill people, typically by [[lynch mob]]s. A tire is soaked in gasoline, placed around the victim's neck, and set on fire.

<gallery widths="200px" heights="160px">
File:Three Boys on a Tire Swing.JPG|Children on a tire swing
File:Intifada in Gaza Strip (FL45956336).jpg|Burning tires in protest
</gallery>

==See also==
{{Div col|colwidth=15em}}
* [[Dry steering]]
* [[List of auto parts]]
* [[List of inflatable manufactured goods]]
* [[Off-road tire]]
* [[Outline of tires]]
* [[Rubber-tyred metro]]
* [[Rubber-tyred trams]]
* [[Shinosaur]]
{{Div col end}}

==References==
{{Reflist}}

==External links==
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{{Wiktionary|inner tube|tire|tyre}}
{{Commons category|Tires}}
* [http://www.nhtsa.gov/DOT/NHTSA/Vehicle%20Safety/Articles/Associated%20Files/brochure.pdf National Highway Traffic Safety Adm "Tire Safety" Brochure] ({{Webarchive|url= https://web.archive.org/web/20201028232022/https://www.nhtsa.gov/DOT/NHTSA/Vehicle%20Safety/Articles/Associated%20Files/brochure.pdf |date=28 October 2020 }})
* [http://www.safercar.gov/Tire U.S. government tire rating and maintenance site]

{{Tires}}
{{Rubber}}
{{Automotive handling}}
{{Powertrain}}
{{CarDesign nav}}
{{Authority control}}

[[Category:Tires| ]]
[[Category:Auto parts]]
[[Category:Rubber]]
[[Category:Scottish inventions]]