Tyre Glossary T-Z


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Traction: A term used to describe the force of friction between the drive wheel and the road.

Tread: This is the part of the tyre that comes into contact with the road.

Tread Depth: The measurement between the top of the tread runner to the tyres deepest grooves. The legal limit for tread depth is a minimum of 1.6mm.

Tread Wear Indicator:  These are narrow bands in the tread grooves which provide a visual warning when tyres need changing. These become visible if the tyre falls below the legal limit of 1.6mm.

Tubules: Usually found in radial tyres these are constructed with an inner liner to protect against loss of pressure during normal use.

Tyre Compound:  A "mix" or combination of raw materials used in the manufacture of the rubber compound of the tyre itself. By varying the percentage or the composition of the materials applied, manufacturers can produce different tyres for various purposes and with different performances.

Tyre Information Found in the vehicle handbook or sometimes on the inside sill of the driver’s door, this information outlines the recommended pressure, rim size and load capacity. :

Tyre Pressure: This is the amount of air inside the tyre measured in PSI or in Bar. The correct pressure can be found in the vehicle handbook and usually on the inside of the petrol tank flap. This should be changed regularly as tyre pressure reduces gradually over time. Note, tyres should never be inflated beyond the maximum pressure specified in the vehicle manufacturers handbook.

Tyre Pressure Monitoring System (TPMS): This device, usually attached in the wheel wall or to the tyre, can send information to a dashboard display whilst the vehicle is in use. If there is a loss in pressure the driver is alerted. Note: run-flat can only be used if a vehicle is fitted with a TPMS.

Tyre Wall: The area on the tyre where information about the tyre is displayed.

Under Inflation:  A tyre with insufficient air pressure.

Understeer (see also Oversteer): When a car fails to respond to drivers steering and continues to drive straight. This is the opposite to Oversteer.

Valve: Allows the tyre to be inflated to the correct pressure. Valves are usually made of rubber, with a metal core assembly with a screw on dust cap. There are 2 standards lengths, short for most alloy wheels and long for steel wheels which have a plastic wheel trim.

Winter Tyres (also see Cold Weather Tyres ): Winter tyres are constructed using special compounds designed for use in winter driving conditions including temperatures below 7 degrees Celsius. Can include multiple blades or sipes for increased grip in slippery conditions.