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All Season Tyres: Tyres built with a specialist compound and tread pattern. These tyres offer acceptable performance during both winter and summer months, and generally carry on the sidewall the snowflake emblem which means they are approved by overseas authorities for use in winter conditions. Find out more about all season tyres.

Aspect Ratio/Tyre Profile: The depth of a tyre’s sidewall, as a percentage of its width. This can be found on the sidewall of the tyre.

Aquaplaning: When a thin layer of water prevents tyres from contacting the road. Lack of grip causes vehicles to veer out of control due to lack of braking, turning, cornering or accelerating ability.

Block: A tread block is a single element of a tread pattern. Shapes may vary depending on the tread design.

Carcass: The network of cords that give a tyre its shape and structure.

Compound: Mix of crude materials used to produce tyres. Differing compounds are created by varying the compound components, to create tyres for different purposes.

Load Index: The code included in the tyre size which indicates the maximum weight a tyre can handle.

Low-Profile: A tyre is classified as low-profile if the sidewall depth to width ratio is less than 50%. Tyres with a ratio of 30% are known as ultra low profile tyres.

M&S Tyres: A designation of tyre favoured in the USA. M&S stands for Mud and Snow. These tyres generally have more sipes than a summer tyre. Experience has shown that these tyres, whilst effective in summer conditions and in the wet, are not as effective as All Season Tyres or Winter tyres which may have considerably more winter capability. They might not carry the snowflake emblem on the sidewall and hence may not be suitable for use in countries that require specialist winter tyres during the cold season.

Noise Level: The measurement of noise, in decibels from a tyre in use. External noise is measured against the EU noise pollution limits for EU tyre labelling readings.

OE [Original Equipment] Tyres: Tyres made by one company, which are fitted during manufacture/construction as original equipment to another company’s vehicle.

Rolling Resistance: The rate at which a tyre naturally rolls. Less rolling resistance means less energy to keep a constant speed, which in turn means lower fuel consumption.

Run Flat: Technology which enables a tyre to remain inflated for a period of time, after puncturing.

Shoulder: The section of a tyre where the sidewall and the footprint meet.

Sipes: Indentations, of varying thickness, in the tread pattern of a tyre to maintain and improve grip.

Sidewall: The area on a tyre between the shoulder and the beading. The rubber that protects the tyre carcass from side bumps e.g. kerbs.

Speed Rating: Displays the maximum speed limit for a tyre. Included in the tyre size

Summer Tyres: Known as 'standard tyres' as opposed to Winter or All Season Tyres. The tread patterns and compounds used in these tyres give their best performance in temperatures over 7°c. Find out more about summer tyres.

Tread: The footprint of the tyre, which includes a tread pattern; made up of blocks, sipes and grooves to enable effective traction and grip.

Tyre Size: A combination of measurements and ratings. Tyre size requirements differ between vehicle make and model. Tyre size can be found on the sidewall of each tyre manufactured.

Winter Tyres: Tyres made with a specialist compound which stays flexible below 7°c and will include a specialist tread pattern for top performance in wintery conditions. Find out more about winter tyres.

If you require further tyre information, do not hesitate to contact one of our trained specialists at your local Merityre branch.


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