Tyre Glossary
Air Pressure
The amount of air inside your tyre. Measured in either pounds per square inch (psi) or bars. The correct pressure for tyres for each vehicle can usually be found in the handbook.
Alignment
Alignment is a process that ensures the suspension, wheels and steering are all in accordance with the manufacturers specification for the best way the wheels should be pointing.
Aspect Ratio
A way of expressing a tyre's height as a percentage of its section width. This figure can be found on the sidewall of the tyre.
Balancing
Bar
Bar is a metric unit for air pressure for your tyres.
Bead
A ring of steel wire, within a rubber wrap. This helps to hold the tyre to the rim of your car.
Casing
This is the inside of the tyre sitting underneath the tread and sidewalls.
Cold Inflation Pressure
Cold Inflation Pressure is the tyre pressure before the tyre has been able to heat up from driving.
Cold weather tyres
A tyre designed to give better grip below temperatures of 7 degrees
Footprint
The area of the tyre's tread that comes into contact with the ground.
Innerliner
The innerliner prevents air from seeping out of the tyre in a tubeless tyre.
Load Index
This is a code that ranges from 0 to 279. It identifies the maximum weight a tyre can bear at the speed indicated by a speed symbol under certain service conditions.
Low profile tyres
Low profile tyres are a description of tyres that are quite thin in comparison to the radius of the wheel itself.
Maximum Inflation Pressure
The maximum pressure that your tyre can be inflated up to.
Pounds per square inch
The imperial unit for air pressure for your tyres.
Rim
The metal edge of the wheel on which the bead is seated. This enables the tyre to be supported correctly.
Rolling Resistance
The energy necessary to keep a tyre moving at a constant speed.
Run-flats
Run-flat tyres enable vehicles to be driven at reduced speeds for a limited time. After this time they are to be replaced.
Section Height
Section Width
The measurement of the tyre from one side to the other side.
Shoulder
The shoulder can be found where the sidewall and tread meet on your tyre.
Sidewall
The sidewall is the area between the bead and the start of the tread on your tyre.
Sipes
Sipes are slits in the tread designed to improve the grip of the tyres in wet conditions.
Size
The size is used to identify a specific tyre. This includes identifying width, construction type, aspect ratio and rim size.
Speed Rating
Speed rating is used to indicate the variance of speeds at which a tyre can carry a load under a range of different conditions.
Made of a mixture of rubber, chemicals, fabric and metal. A tyre's job is to give the car traction on the road in a variety of conditions and to cushion the car from any possible shock.
Tread
The tread is the part of the tyre that comes into contact with the road.
Treadwear Indicator
The Treadwear indicator includes narrow bands in the tread grooves that provide a visual warning to a tyre needs changing.
Tread Width
The Tread width is the portion or area of the tyres width that is covered by a tread pattern.
Underinflation
Underinflation is a condition that occurs when there is not sufficient air pressure in a tyre.
