Tread
From Wikipedia, the free encyclopedia
The tread of a tire or caterpillar track refers to the pattern visible on its circumference that makes contact with the road. As tires are used, the tread is worn down limiting their effectiveness in providing traction. A worn tire tread can be replaced with a process known as retreading.
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[edit] Tires
[edit] Street tires
The gaps between the rubber sections are designed to allow water to be expelled from beneath the tire and prevent hydroplaning. The proportion of rubber to air space on the road surface directly affects its traction. Tires intended for dry weather use will be designed with minimal gaps to increase the contact patch. Generally there is a tradeoff of tread friction capability; deeper tread designs often enhance safety, but simpler designs are less costly to produce and actually may afford some roadway noise mitigation. Tires without any tread patterns are known as slicks and are generally used for racing only.
Street tires will also include wear limit indicators in the form of small raised bridges between the treads. When the treads are worn down enough to result in the limit indicators making contact with the road then the tire is deemed to be at the end of its service life. Brake pads use similar indicators in the form of notches on their surface that disappear when they are used.
[edit] Off-road tires
Off-road tires used in mud or dirt feature individual knob patterns to allow the tire to bite into the road and leverage the sides of the tread to get a better grip. Given the smaller contact patch, these tires tend to wear quickly when used on asphalt.
[edit] Mountain bike & motorcycle tires
Mountain bike and some motorcycle tires feature tread patterns similar to off-road tires used on cars and trucks but may sometimes include an unbroken tread that runs along its center. This feature provides better traction and lower noise on asphalt while the bike is vertical while retaining its ability to provide lateral grip when the bike is leaning.
[edit] Caterpillar tracks
Caterpillar tracks such as those used on military tanks or construction machines have metal track segments which may be rubber-coated. They usually do not feature tread patterns, because these would offer little additional grip given the weight of the tracked vehicle.
