Tread Wear Indicators

Most tyre manufacturers build a tread wear indicator into the tread pattern.
This a small rubber moulding raised 1.6mm above the base of the tread groove so that when the adjacent tread has worn down to this level it indicates the tyre should be changed. A few tyres have an additional indicator at 3mm to indicate the tread depth is getting near the limit. Most car and light van tyres have 8mm tread when new.

Minimum Tread Depth

The requirements in the UK are that the grooves of the tread pattern of every tyre fitted to a vehicle shall be of a depth of at least 1.6mm throughout a continuous band comprising the central three-quarters of the breadth of tread and round the entire outer circumference of the tyre.

It is not advisable to run the depth of the tyre right down to the legal limit as this will have a negative effect on the car’s handling, ability to grip the road and stopping capability. Ideally a tyre should wherever possible be removed at 3mm.

Tyre Condition

A tyre used on a vehicle or trailer must not have any cut or damage to the exterior of the tyre which is more than 25mm or 10 percent of the section width, which exposes the cords or ply of the tyre or any internal or external lump bulge or tear caused by separation or partial failure of the structure. It is a requirement of using a vehicle on the road that the tyres fitted shall be in good condition and suitable in all respects, including inflation pressure, for the use to which the vehicle is being put.

Penalties

It is an offence to use a tyre which has any defect (not just illegal tread depth). The penalty for an offence is a fine at level 4 of the standard scale (currently up to £2,500), compulsory 3 point endorsement and discretionary disqualification. Each faulty tyre is a separate offence.