Tread Depth & Safety
Tread Depth
A new car tyre begins life with approximately 8 mm of tread, the minimum legal tread depth is 1.6 mm, most motoring organisations recommend changing at 2 mm while the majority of manufacturers recommend changing at 3 mm.
As the tread depth reduces, the tyres ability to remove water from the road surface also reduces, increasing the risk of aquaplaning and because the tyre is unable to transmit traction and braking forces to the road as effectively the vehicles stopping distances increase.
Tread depth new 8mm.
- 7mm 16% worn
- 6mm 31% worn
- 5mm 47% worn
- 4mm 63% worn
- 3mm 78% worn
- 2mm 94% worn
- 1.6mm 100% worn
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 metres stopping distance in wet conditions.
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. If the surface of the tread rubber is level with these raised areas the tyre tread depth is most likely very close to the legal limit of 1.6 mm, or could even be below it!
The tyre should be checked and if necessary changed, because you may no longer be driving in sufficient safety and you could be breaking the law.