Tyre Glossary

When purchasing new tyres you may encounter a surprising amount of complex tyre terms. To help you understand and choose the right tyres for your vehicle, Dexel Tyre & Auto Centre have created a helpful tyre glossary.

Alloy Wheels – Unlike standard wheels which are made from steel, alloy wheels are made using an alloy, which is a mixture of aluminium and magnesium. They are lighter in weight, to improve steering performance, stronger and usually provide a better aesthetic.

All Season Tyres – Tyres that are built with a specialist compound and tyre tread to provide adequate performance in all weather conditions. Unlike dedicated seasonal tyres, they do not excel in summer or winter, however they are ideal for motorists who cannot fit and store two sets of tyres. Find out more about all season tyres.

Aquaplaning – This is the term given to the action where your tyres lose contact with the surface of a wet road. When aquaplaning, tyres lose grip and this can result in skidding and sliding on a layer of water. This can be made worse by driving on tyres that do not have sufficient tyre tread or by driving too quickly in wet conditions.

Aspect Ratio – The aspect ratio is the second set of two digit figures in the tyre size that can be found on your tyre sidewall. This figure indicates the tyre’s height as a percentage of its width. You will need to know this number when purchasing new tyres for your vehicle.

Budget Tyres – Tyres that are manufactured as a cheaper alternative to premium manufacturer tyres. They are usually constructed using cheaper materials and subject to less testing than their more expensive counterparts. Learn more about budget tyres.

Carcass – The carcass of the tyre is the internal cord layer that sustains load, absorbs shock and gives the tyre its structure. It is composed of several parts including the tread, sidewall and shoulder.

Contact Patch – Also known as the footprint, the contact patch is the area of the tyre that retains contact with the surface of the road.

Handling – The handling of the tyre is how it responds to the driver in terms of braking, cornering, acceleration and other demands. Good handling is crucial when it comes to safety on the road and driving performance.

Load Index – indicated on your tyre sidewall, the load index is a numerical code which relates to the maximum weight that your tyre can carry.

Original Equipment [OE] – This is the brand of tyre that was selected by your vehicle manufacturer to be fitted to your car. In some cases, there are more than one OE brand fitment.

Part Worn Tyres – Tyres which are sold after having being used are referred to as part worn tyres. Fitting part worn tyres to your vehicle can be highly dangerous as many are sold illegally and some contain defects.

Reinforced Tyres – Reinforced tyres are constructed with strengthened sidewalls so that they can handle heavy loads.

Run Flat Tyres – This is a tyre designed especially to remain inflated for a short period of time following a puncture. Run flat tyres usually cannot be repaired after suffering damage, however, they enable motorists to drive to safety.

Shoulder – The shoulder of the tyre is the part of the tyre which sits between the sidewall and the tread. It is one of the thickest components of the tyre and provides stability when driving.

Sidewall – Sat between the shoulder and the bead, the sidewall of the tyre is the rubber that protects the tyre from damage. Tyre manufacturers print important information on this area of the tyre and these are known as tyre sidewall markings.

Sipes – Located on all tyres, sipes are grooves or channels that have been cut in to the tyre tread to improve grip and traction in wet conditions.

Speed Rating – The speed rating of a tyre is displayed as the last letter of the tyre size on the tyre sidewall. It translates as the maximum speed the tyre is able to safely maintain when it is correctly inflated and carrying its maximum load.

Summer Tyres – Also known as standard tyres, summer tyres are designed with compounds and tread patterns that are optimal for driving in temperatures over 7oc. These are often fitted to your vehicle as standard. Summer tyres offer a greater performance than winter or all season tyres in warm conditions. Find out more about summer tyres.

Tread Wear Indicator – Some tyre manufacturers use tread wear indicators to notify motorists when it is time to replace their tyres. These are small bands, shapes or symbols which become visible if the tyre tread is close to the legal limit of 1.6mm. You should not fully rely on tread wear indicators, but also endeavour to frequently check your tyre tread.

Tyre Tread – The tyre tread refers to the rubber that covers the tyre and makes contact with the surface of the road. The tread will be designed with a pattern including sipes, grooves and blocks to enable handling, grip and traction. Over time, it will naturally wear so it is important that you know how to check your tyre tread.

Tyre Pressure – Your tyres are filled with pressurised air and this enables them to provide greater handling capabilities on the road. Tyre pressure is measured in PSI or bar, and it is important that you maintain the correct pressure to keep yourself safe on the road. Learn how to check your tyre pressures here.

Wheel Alignment – Also known as tracking, wheel alignment is a process that involves adjusting the wheels to the optimum angles so that your tyres wear evenly and driving is as safe and stable as possible. Learn more about wheel alignment.

Winter Tyres – Constructed with a large number of sipes and a specialist compound which does not stiffen at cold temperatures, winter tyres are designed to provide safe and stable performance in winter conditions. Find out more about winter tyres.

For more information on tyre terminology or if you require further tyre advice, contact a specialist at your local Dexel Tyre & Auto Centre branch.