Advice & Guidance on Tyre Tread and UK Tyre Law
UK Tyre Law : Tyre tread and the Law
The law requires car tyres to have a minimum tread depth of 1.6mm in a continuous band around the central three quarters of the tyre. To help you judge how much tread you have on your car tyres, manufacturers often mould tread bars at roughly 1.6mm.

Tread depth indicator

This tyre is very close to being - or has
just become - illegal
If you can see these bars your tyres are about to become illegal and unsafe. However, for optimum safety, most manufacturers recommend that your tyres are changed at 3mm.