Editing Tire (section)

====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>