Tyre Glossary

Buying, maintaining and changing tyres can involve a lot of complex jargon which makes these simple processes more difficult than they need to be. At Setyres, we realise that not everyone is a tyre expert but there are some phrases which will prove useful whilst you are on the road.

This is why we have compiled a list of the most frequently used tyre terms. Knowing what certain words mean in relation to tyres will ease the pressure of choosing new tyres and explaining any tyre problems you may experience.

For further information or help defining a tyre term that we have not listed, simply call or visit your local Setyres centre where one of our friendly tyre experts will be on hand to help.



Alignment

Wheel alignment, also called tracking, is a process which ensures that the wheels point in the right way and ensures your vehicle drives in a true straight line. Wheel alignment can be affected by small driving annoyances such as hitting a kerb or pothole and it is important to have your wheel alignment checked if you notice any of the warning signs which are listed here.



All Season Tyres

These are tyres which have been built to offer an acceptable performance during both winter and summer months, due to a specialist compound and tyre pattern.

Read about all season tyres in more detail here.



Alloy Wheels

Alloy wheels are wheels which are made from an alloy of aluminium or magnesium, rather than steel. They generally provide greater strength than steel wheels and due to their lighter weight, alloy wheels offer improved steering.



Aquaplaning

This is when your vehicle slides uncontrollably whilst driving in wet conditions. It occurs when a layer of water sits between the tyre and the road surface. Some tyres are constructed with specialist tread patterns to help counteract and prevent aquaplaning from happening.



Aspect Ratio

This is a way of expressing the tyre’s height as a percentage of its section width. This can be found on the sidewall of the tyre.



Bead

A ring of steel wire which helps hold the tyre to the rim.



Block

A tread block is an element of a tread pattern. Blocks can be different shapes and are designed by tyre manufacturers for certain driving specifications.



Carcass

Also known as casing, the tyre carcass is the skeleton of the tyre which is made up of a network of cords and gives the tyre its structure.



Compound

This is the mixture of materials used to construct tyres. Compounds are usually created using raw materials such as rubber and carbon. Manufacturers may use differing compound for tyres which have different purposes, for example a winter tyre designed for tough conditions will be made using a different compound to a summer tyre which does not need to offer snow and ice traction or resistance to cold temperatures.



Footprint

The footprint of the tyre refers to the area of the tyre which remains in contact with the road.



Load Index

This figure indicates the maximum weight that a tyre can carry at a certain speed and is specified by the manufacturer. This figure can be found on the tyre sidewall. For more information on finding out the load index of your tyres click here.



M&S Tyres

M&S, or mud and snow tyres can be identified by a mountain and snowflake symbol branded on the tyre sidewall. This marking means that these tyres met the required performance in snow testing. These tyres are for specific use in tough winter conditions and will not offer an effective performance during summer.



Maximum Inflation Pressure

his is the maximum pressure that a tyre can be inflated to. For advice on finding this figure and further information regarding visit our tyre pressure page.



PSI

PSI (pounds per square inch) is the imperial unit for air pressure.



Reinforced tyres

This is the name given to tyres with strengthened sidewalls to deal with heavy loads.



Rim

The metal edge of the wheel. The bead then sits on this rim and holds the tyre to the wheel.



Rolling Resistance

The rolling resistance is the energy needed to keep a tyre moving at a constant speed. Less rolling resistance means less energy to keep a constant speed, which in turn means lower fuel consumption.



Run-Flat Tyres

This is a special tyre of tyre which will remain inflated for a short period following a puncture. These tyres can then be driven on, at a reduced speed, until the driver can have them replaced.

Learn more about run flat tyres here.



Shoulder

This is an area of the tyre found where the sidewall and tread meet.



Sidewall

The tyre sidewall sits between the shoulder and the beading and it the rubber that protects the carcass of the tyre. Important information about the tyre is printed on the tyre sidewall. Take a look here for information on how to read your tyre sidewall markings.



Silica

A compound used in the construction of tyres, silica is a reinforcing filler which provides higher mileage and lower rolling resistance.



Sipes

Sipes are slits in the tread blocks designed to enhance grip and provide resistance against aquaplaning.



Speed Rating

This indicates the maximum speed limit for a tyre and can be found on the tyre sidewall. For more information on finding this figure click here.



Summer tyres

Summer tyres are tyres which have been designed for a superior performance in temperatures over 7ºc. Due to specially designed tread patterns and compounds used in these tyres, they are optimal for summer driving.

Read about summer tyres in more detail here.



Tread

The tyre tread is the footprint of the tyre and includes a tread pattern. Tread patterns are designed by the manufacturer and usually vary between different types of tyres. These patterns are made up of an arrangement of blocks, sipes and grooves and enable effective traction and grip.



Tread Depth

This is the measurement between the top of the tread to the tyres deepest grooves and must remain above at least 1.6mm, which is the legal minimum. There will be a tread wear indicator present on your tyre which will provide a visual warning when your tread depth too low. You will only see your tread wear indicator once your tread depth is below the legal minimum. Take a look at our advice for further information on tyre tread depth.



Tyre Pressure

This is the amount of air inside your tyre and is measures in PSI. You need to ensure that you regularly check that your tyres are correctly inflated to the right level. This level can be found in your vehicle handbook. For more information on tyre pressure take a look here.



Tyre Size

This information is a combination of different measurements and can be found printed on the sidewall of your tyre.



Winter tyres

Winter tyres are designed specifically to cope with cold weather and tough winter conditions. They are constructed using compounds that can deal with cold temperatures and are often modified to offer improved grip on ice and snow.

Read about winter tyres in more detail here.