Editing Tire (section)

== 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}}</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 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 (''[[Glass transition|Tg]]'' = -100&nbsp;°C) having high hysteresis and thus offering good wet grip properties, with the properties of [[polystyrene]], which is a glassy polymer (''Tg'' = 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>