The tread pattern on an asymmetric car tyre changes across the tread with different parts adapted for particular functions.
- The outside edge consists of large stiffer tread blocks which help with cornering.
- The inner tread blocks are smaller and designed to shift water and improve wet grip.
- The middle of the tread usually has a continuous rib to help straight line stability.
The sidewalls will be clearly marked to make sure that an asymmetric tyre is fitted the right way round on the wheel to benefit from the tread block arrangement.
Directional tyres usually have a chevron or arrow pattern in the tread and are designed to work in only one direction of rotation.
- Directional tyres are better at dispersing water that builds up in front of the tyre.
- They may also reduce road noise and improve directional stability.
Directional tyres must rotate in the right direction, clearly marked on the sidewall of the tyre.
If a directional tyre is fitted the wrong way round, the tyre won't be dangerous, but you won't gain the benefits of its design.
Some high performance cars are fitted with tyres that are both directional and asymmetric. These must be fitted the right way round on the wheel and on the correct side of the vehicle.
If asymmetric or directional tyres are fitted incorrectly – the wrong way round or rotating in the wrong direction – your car will fail its MOT.
3 February 2017