Tyre and safety experts believe the 1.6mm legal minimum is insufficient to guarantee safety – most recommend a minimum tread depth of 3mm for tyre replacement. Tests by UK technical organisation MIRA found that, once tyres are below 3mm, stopping distances increase dramatically.
The difference in wet braking distance between a tyre worn to 3mm and one worn to 1.6mm can be as much as 44%.
Worn tyres are particularly dangerous in the wet because a tyre’s tread helps disperse water away from the contact patch between tyre and road. If there’s less tread depth, less water can be shifted, increasing the risk of aquaplaning and losing grip.
In heavy rain, each tyre can shift one gallon of water every second, illustrating just how hard tyres work. Simply put, deeper tread means they can work better, improving grip.