Darra Tyres, Brisbane

Air Pressure
The amount of air inside your tyre expressed as a pressure. Normally measured in either pounds per square inch (psi) or bars. The correct pressure for tyres for each vehicle can usually be found in the cars handbook or on the tyre sidewall.

Wheel 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. In laypersons terms, it makes adjusts various tyre, steering and suspension variable to ensure the wheels point straight, your steering wheel is centred when the wheels point straight and finally that the tyres are flat on the road and not tilted over.

Alignment is especially important in ensuring the longevity of your tyres, they will wear much quicker if they are not aligned.

Aspect Ratio
It’s a way of expressing a tyre’s height as a percentage of its width. This figure can be found on the sidewall of the tyre. 195/65R13 it would be the 65.

Balancing
Tyre balancing is a technical process which ensures that when the tyre and the wheel spin it’s weight is equally distributed throughout tyre. Unbalanced tyres often make the steering shake and therefore you need to come and see the team.

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 vehicle.

Casing
This is the inside of the tyre sitting underneath the tread and sidewalls. Normally if you have a retread tyre you will be using the old casing, the tread will be replaced.

Cold Inflation Pressure
Cold Inflation Pressure is the tyre pressure before the tyre has been able to heated up from driving. Heat expands air therefore you will find that your Cold Inflation pressure will be less that the Working Pressure of a tyre.

Cold weather tyres
A tyre designed to give better grip below temperatures of 7 degrees. There are rare in most areas of Australia. You are likely to find these in European climates especially Scandinavian countries where they have many months of ice. In these countries they have a summer and a winter set of tyres.

Footprint
The area of the tyre’s tread that comes into contact with the ground.

Inner Liner
The inner liner 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. These are normally used in racing but they also have uses in industrial vehicles such as bobcats.

Maximum Inflation Pressure
The maximum pressure that your tyre can be inflated up to. It may not bust immediately but you certainly wouldn’t want to drive in it.

Pounds per square inch – PSi
The imperial unit for air pressure for your tyres.

Retread
A tyre where a used cased is renewed by replacing the tread.

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
Tyre height from the rim to the outer tread.

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. This is the part of the tyre with many bits of information about the tyre, date of manufacture, speed rating, height, load weighting etc.

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.

Tyre
Made of a mixture of rubber, chemicals, fabric and metal. A tyre’s job is to give the vehicle traction on the road in all manner of conditions and to cushion the vehicle from any possible bumps along the way.

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. Your tyres must legally be changed once they have warn down to the indictor, even if only one side of the tyre has worn. Fines and loss of points will result from unroadworthy tyres.

Tread Width
The Tread width is the portion or area of the tyres width that is covered by a tread pattern.

Under Inflation
Under inflation is a condition that occurs when there is not sufficient air pressure in a tyre. Checking your tyres pressure or seeing the team on a regular basis will solve this or indicate a problem such as a slow leak.