What is the Legal Tyre Tread depth? And why it matters

Published Date: 27th Apr 2016

The black rubber circles that surround your alloys matter much more than many people know. If your tyre tread depth is low then even the most sophisticated anti lock braking, stability control or autonomous braking system in the world will not help you. All these systems rely upon the direct grip provided by the tyres to work efficiently.

The tread depth is the measured from the bottom of the grooves to the top of the rubber in contact with the road. This measurement is a very important factor in how well your tyres will perform on the road and in bad weather conditions.

The legal tyre tread depth minimum

Whether your car is in for MOT or traffic police do a roadside inspection on your car, the legal limit for your tyre tread depth is 1.6mm. It has to be this depth across the central three quarters of the tyre.

The Industry safety experts recommend changing the boots on your vehicle when the tread gets down to 3mm. This is down to the performance of the tyre starts to drop off resulting in longer stopping distances in the wet and dry.

The tread grooves act as a channel for the surface rain water and pump the water out the other side, so the surface of the tyre can remain in contact with the road. As the tread depth decreases so does the space for the water to dispel. This can result in aquaplaning, when the resulting water on the road cannot pass through the grooves efficiently and the tyre looses grip.

It’s good practise to inspect your tyres with a tread depth gauge that can be bought online at a small cost. Failing the proper measuring tools you can use a 20 pence coin to give a rough idea of the tread depth. The outer edge to the inner border line of the coin is approximately 3mm and you should be looking at changing them if your tread dips below this.

Most modern tyres have wear indicators built into the tread grooves. They are little raised bumps spread across a horizontal section of the tyre. These are usually set at 3mm and when the rest of the tyre tread is level with these indicators, you know it’s time for some new tyres.