How Tyre Tread Depth Affects Braking Distance

Tread depth directly affects how quickly water is expelled from under the contact patch. Shallow tread lengthens stopping distance in the wet and raises the speed at which hydroplaning begins.

What happens in the wet

Grooves channel water away; sipes bite the road film. As depth drops, the tyre’s effective “bite” and volume to store water both shrink — grip falls non-linearly below about 3 mm for many patterns.

Dry roads still matter

Thin tread flexes differently and can overheat faster under hard braking. Debris penetration risk rises.

Test data takeaway

Independent tests consistently show worn tyres add metres to emergency stops versus new tyres on identical cars — the exact gap depends on compound, pattern, and road temperature.