How to Check Tyre Tread Depth

Your tyres are the only contact between your car and the road. Worn tread reduces grip in wet conditions, increases stopping distances, and will fail an MOT at /services/mot-testing. Checking tread depth at home takes minutes and could prevent an accident or an unexpected bill. Here is how to do it properly.

The legal minimum tread depth

UK law requires at least 1.6 mm of tread across the central three-quarters of the tyre, around the entire circumference. Falling below this limit can result in a £2,500 fine and three penalty points per tyre. Most safety organisations recommend replacing tyres at 3 mm, as wet-weather performance drops significantly below this level.

The 20p test

Insert a 20p coin into the main tread grooves at several points across the tyre. If the outer band of the coin — the part with the lettering — is hidden by the tread, you likely have more than 1.6 mm remaining. If the band is visible, your tread may be too low and you should get a professional measurement.

Check the inner, centre, and outer edges of each tyre. Uneven wear across the width suggests incorrect inflation, wheel alignment issues at /services/wheel-alignment, or suspension problems.

Using a tread depth gauge

A tread depth gauge costs a few pounds and gives an accurate reading in millimetres. Place the probe into the groove, press flat, and read the scale. Measure at least three points per tyre. Gauges are more reliable than the 20p test and worth keeping in your glovebox.

Tread wear indicators

Modern tyres have small raised bars in the grooves set at 1.6 mm. When the tread wears flush with these bars, the tyre has reached the legal limit and must be replaced. Look for a triangle or TWI marking on the sidewall showing where to find the indicators.

Other signs of tyre problems

Bulges, cuts, cracks, and exposed cord mean the tyre is unsafe regardless of tread depth. Replace immediately. Frequent pressure loss may indicate a slow puncture — we offer puncture repairs at /services/tyres where the damage allows.

When to visit a professional

If any tyre is near or below 3 mm, book a free tyre safety check at Pickwell Autohub. We supply and fit premium and budget brands, with fitting and balancing included. Prices start from £50 for a 15-inch tyre. Book at /booking or visit /services/tyres for more information.