Ultimate Tyre Glossary
Monday 3rd April 2023
Here at Formula One Autocentres, we understand that not everyone is an expert on tyres, and when you’re shopping for a new pair or checking the condition of your current set, there can be a lot of difficult terminology to get to grips with. This guide will break down some of the common words and phrases used when discussing tyres.
If you’re ready to buy your next set of tyres, you can easily buy tyres online, simply enter your reg and choose your tyres.
Air Pressure
The air pressure in a tyre is a measurement of how much air is in your car tyre. The correct air pressure is essential in maintaining the correct level of grip on the road’s surface and ensures your tyres wear evenly. To find out more about the correct air pressure for your tyres, read our helpful guide.
Alignment
Wheel alignment is the angle and direction your wheels are set at. Your wheel alignment can result in your tyres wearing out more quickly, or unevenly. Your wheels can easily become misaligned from hitting potholes or kerbs. For peace of mind, bring your car in for a free wheel alignment check.
All Weather Tyres
All-Season or All-Weather tyres are tyres that blend the technology of both summer and winter tyres to adapt to both summer and winter weather conditions.
Aquaplaning
Aquaplaning is caused when there is a layer of water between the road and the tyre. This causes the tyres to lose grip on the road and can cause the driver to lose control of the car.
BAR
BAR is a unit of measuring pressure - 1 BAR equals 14.50 pounds per square inch of pressure - and can be used to measure the level of air pressure in tyres.
Balancing
Unbalanced wheels are caused by uneven weight distribution on your wheels, this could be due to the circumference of your wheels not being perfectly round and can result in uneven tyre wear or even suspension damage. If you’re concerned about your wheel balance or haven’t had it checked in the last two years, take a look at our wheel balancing service.
Bead
The bead of the tyre is part of the tyre that sits on the wheel. Wheels have a small groove for the bead of the tyre slots into when the tyre is properly inflated.
Block
The tyre block is the raised rubber segments of the tyre that make contact with the road’s surface.
Braking distance
The braking distance is the distance travelled before coming to a complete stop when applying the brakes while driving.
Casing
The tyre casing is the layer of material underneath the tyre tread.
Contact area
The contact area is the area of the tyre that comes into contact with the road. Surprisingly, the contact area is smaller than the size of your hand.
Cord
Cords are used in tyres to help reinforce the shape of a tyre and provide rigidity to the tyre.
EU Tyre Label
The EU Tyre label system rates the wet braking performance of the tyre, fuel efficiency and noise level. Even though we have left the EU, this labelling system is still used in the UK. Read our guide explaining how to read a tyre label.
Load index
The tyre load index is the maximum weight a tyre can support when properly inflated.
Low Rolling Resistance
Low-rolling resisting tyres are designed to reduce energy loss as the tyre is rotated. This improves fuel efficiency. This is because they are made from lighter rubber compounds and use shallower tread patterns.
Maximum Inflation Pressure
The maximum inflation pressure is the highest amount of cold inflation pressure that a tyre can handle. In warm conditions, your tyre pressure will expand further, so it’s important not to over-inflate your tyres.
Minimum Tread Depth
The minimum legal tread depth in the UK is 1.6mm. However, we recommend replacing your tyre at 3mm for maximum safety. Learn more about how to check your tyre tread depth in our guide.
PSI
The PSI is the usual unit of measurement of air pressure for your tyres. It stands for Pounds per Square Inch.
Rim width
The rim width of a tyre is the measurement between the two inner edges of the tyre.
Run Flat Tyres
Run flat tyres are tyres designed to allow you to continue to drive with a puncture for a limited amount of time at a reduced speed. To find out more about run flat tyres read our helpful guide.
Sidewall
The tyre sidewall runs from the bead to the tread. It is the vertical part of the tyre where you’ll find a lot of important information about your tyres such as the size, type, load capacity and tyre speed rating.
Sipes
The sipes on a tyre are small narrow grooves that are designed to improve the handling of your vehicle in wet or icy conditions. Sipes can also help reduce the amount of noise created by the tyre and generally help the performance of the tyre.
Size
Your tyre size is displayed on the sidewall of your tyre and defines your tyre’s width in millimetres, the height of the tyre’s sidewall and the diameter of the wheel rim in inches.
Speed Rating
Your tyre speed rating is also marked on the sidewall of your tyre. This indicates the top speed that your tyres will perform safely at.
Tread
The tyres’ tread is the pattern of grooves designed to come into contact with the road’s surface. Your tyre tread is the part of your tyre that grips the road, reduces aquaplaning and protects your tyre from wear and tear.
Tread Wear Indicator
Tyre tread wear indicators are narrow notches in the grooves of your tyre tread pattern marked with the letters TWI. They are 1.6mm in height, which means once they are level with your tyre tread, your tyres will be at the legal tyre tread depth limit.
Winter Tyres
Cold weather tyres or winter tyres are tyres designed to perform in cold and icy weather conditions. This is because they do not harden in the cold and stay flexible in temperatures under 7°C.
No matter your tyre needs, our helpful team here at Formula One Autocentres will be happy to help. We offer wheel balancing, alignment and puncture repair as well as fully fitted tyres from just £29.
