A new car Tyre begins life with approximately 8 mm of tread. The minimum legal tread depth is 1.6 mm, however most motoring organisations recommend changing at 2 mm and the majority of Tyre manufacturers recommend changing at 3 mm.
As the tread depth reduces, the Tyre’s ability to remove water from the road surface reduces, increasing the risk of aquaplaning because the tyre is unable to transmit traction and braking forces to the road as effectively. Therefore the vehicle’s stopping distance increases.
Although the legal minimum tread depth is only 1.6 mm, independent research at MIRA shows that Tyres with 3 mm of tread have an average 25% better performance than those at 1.6 mm – which represents an extra 8 meters stopping distance in wet conditions.
Tread wear indicators
You can check how close you are to the legal limit on all Tyres by looking for the tread wear indicators:
These indicators are small raised areas at the bottom of the grooves. Once the surface of the tread rubber is level with these raised areas, the Tyre tread depth is approaching the legal limit of 1.6 mm and you should have your tyres checked and replaced.