The tread of a tire

Tire

A tire or tyre is a ring-shaped covering that fits around a wheel rim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact with the ground...

 or track refers to the rubber on its circumference that makes contact with the road. As tires are used, the tread is worn off, limiting its effectiveness in providing traction

Traction (engineering)

Traction refers to the maximum frictional force that can be produced between surfaces without slipping.The units of traction are those of force, or if expressed as a coefficient of traction a ratio.-Traction:...

. A worn tire tread can often be retread

Retread

A retread, or "recap," is a previously worn tire which has gone through a remanufacturing process designed to extend its useful service life.Retreading starts with a safety inspection of the tire. The old tread is then buffed away, and a new rubber tread is applied to the bare "casing" using...

ed. The word tread is often used incorrectly to refer to the pattern of grooves cut into the rubber. Those grooves are correctly called the tread pattern, or simply the pattern.

Street tires

The grooves in the rubber 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. Design of tire tread has an impact upon noise generated, especially at freeway speeds. Generally there is a tradeoff of tread friction capability; deeper patterns often enhance safety, but simpler designs are less costly to produce and actually may afford some roadway

Roadway noise

Roadway noise is the collective sound energy emanating from motor vehicles. In the USA it contributes more to environmental noise exposure than any other noise source, and is constituted chiefly of engine, tire, aerodynamic and braking elements...

 noise mitigation

Noise mitigation

Noise mitigation is a set of strategies to reduce noise pollution. The main areas of noise mitigation or abatement are: transportation noise control, architectural design, and occupational noise control...

. Tires intended for dry weather use will be designed with minimal pattern to increase the contact patch

Contact patch

Contact patch is the portion of a vehicle's tire that is in actual contact with the road surface. It is most commonly used in the discussion of pneumatic tires, , where the term is strictly used to describe the portion of the tire’s tread that touches the road surface...

. Tires without any tread patterns are known as slicks

Slick tire

A slick tyre is a type of tyre that has no tread pattern, used mostly in auto racing. The first production "slick tyre" was developed by a company called M&H Tires in the early 1950s for use in drag racing...

 and are generally used for racing only, since they are quite dangerous if the road surface is wet.

Street tires will also include wear limit indicators in the form of small raised bridges within the grooves. When the tread is worn down enough that the limit indicators make contact with the road, the tire is deemed to be at the end of its service life. Brake

Brake

A brake is a mechanical device which inhibits motion. Its opposite component is a clutch. The rest of this article is dedicated to various types of vehicular brakes....

 pads use similar indicators in the form of notches on their surface that disappear when they are used.

Off-road tires

Off-road tire

Mud-terrain tyre

A Mud Terrain Tyre is a type of automotive tire which may be fitted as an aftermarket option to four wheel drive vehicles.Mud terrain tires are characterized by large, chunky tread patterns designed to bite into muddy surfaces and provide grip...

s used in mud or dirt feature individual knob patterns to allow the tire to bite into the surface and lever 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.

Mountain bike and motorcycle tires

Mountain bike

Mountain bike

A mountain bike or mountain bicycle is a bicycle created for off-road cycling. This activity includes traversing of rocks and washouts, and steep declines,...

 and some motorcycle

Motorcycle

A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...

 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 at high tire pressure, but retains the ability to provide grip on a soft or loose surface- lower tire pressure or soft ground will cause the side lugs to come into contact with the surface.

Caterpillar tracks

Caterpillar track

Caterpillar track

Continuous tracks or caterpillar tracks are a system of vehicle propulsion in which modular metal plates linked into a continuous band are driven by two or more wheels...

s such as those used on military tank

Tank

A tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility, tactical offensive, and defensive capabilities...

s 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.

See also

• Anti-lock braking system
  Anti-lock braking system
  An anti-lock braking system is a safety system that allows the wheels on a motor vehicle to continue interacting tractively with the road surface as directed by driver steering inputs while braking, preventing the wheels from locking up and therefore avoiding skidding.An ABS generally offers...
  
  
• Forensic tire tread evidence
  Forensic tire tread evidence
  Forensic tire tread evidence records and analyzes impressions of vehicle tire treads for use in legal proceedings to help prove the identities of persons at the crime scene. Every tire will show different amounts of tread wear, different amounts of damage in the form of tiny cuts and nicks...
  
  
• Snow chains
  Snow chains
  Snow chains, or tire chains, are devices fitted to the tires of vehicles to provide maximum traction when driving through snow and ice....
  
  
• Traction vector
• Traction control system
  Traction control system
  A traction control system , also known as anti-slip regulation , is typically a secondary function of the anti-lock braking system on production motor vehicles, designed to prevent loss of traction of driven road wheels...