Tyre Tread Depth in Winter: Legal Limit vs Safe Limit
Written by Petro Olekhnovych, mobile mechanic in Aylesham, Kent
The legal limit explained
For cars, the law requires at least 1.6mm of tread across the central three-quarters of the tread width, around the whole circumference. The outer edges are not part of the measurement, but the tyre also has to be free of cuts, bulges and exposed cords.
The penalty for a tyre below the limit can be a fine of up to £2,500 and three penalty points, and that is per tyre. Four worn tyres could put a licence at risk in one stop.
At the MOT, tread depth and tyre condition are checked as part of the test. Low tread is one of the items we see most on our list of common MOT failures, and it is one of the easiest to spot in advance.
Why legal is not the same as safe in winter
Tread grooves exist to clear water from under the tyre so the rubber can touch the road. As the grooves get shallower they move less water, so stopping distances on wet roads get longer and the risk of aquaplaning rises.
Kent winters are more wet than snowy. Standing water on the A256, slush and grit on the A2 and M20, and leaf mulch on the lanes around Barham and Wingham all ask a lot of your tyres. Cold also hardens rubber on standard summer tyres, which reduces grip further.
That is why many tyre makers and safety groups suggest thinking about replacement at around 3mm. It is advice, not law, but the difference in wet braking between a tyre at 3mm and one at the legal minimum is significant.
Want to pass your MOT first time?
We do pre-MOT checks and fix advisories at your home or work across East Kent.
WhatsApp for a free quote Call 07563 350335 Contact form
Labour £30 to £50 per hour depending on the job. Send your reg number and we will reply with a price before any work starts.
How to do the 20p test
- Park on level ground with the handbrake on and the engine off.
- Place a 20p coin into the main tread grooves at several points across the tyre.
- Look at the outer band on the coin. If it is hidden, the tread is likely above 1.6mm.
- If you can see the outer band, the tyre may be close to or below the limit. Get it measured properly.
- Repeat at several places around each tyre, as wear is often uneven.
Most tyres also have tread wear indicators, small raised bars in the bottom of the grooves. When the tread is level with those bars, the tyre is at the legal limit.
Other tyre checks worth doing
- Uneven wear. Wear on one edge can point to tracking or suspension problems, often after hitting potholes. See our guide on pothole damage in Kent.
- Bulges or cuts in the sidewall. A bulge means internal damage and the tyre should not be driven on.
- Pressures. Pressures drop as temperatures fall, so check them cold, using the figures in the handbook or door pillar.
- Age. Rubber hardens and cracks with age even when the tread looks fine.
- The spare, if your car has one.
When to stop driving
Do not drive on a tyre with a visible bulge, exposed cords, a deep cut or one that is losing pressure quickly. If the car feels unstable or pulls sharply, pull over safely and arrange recovery or a wheel change. Our winter car checklist covers what else to check before the cold weather sets in.
How we can help
On any visit, from a service to a pre-MOT check, we measure tread depth with a gauge, inspect sidewalls and check pressures. We also look at the brakes and suspension, because uneven tyre wear is often a clue to another problem. We do not carry out MOT tests, but we can tell you what is likely to fail before you book one.
Labour is £30 to £50 per hour depending on the job, with a quote before work starts. Send your reg and postcode on WhatsApp 07563 350335 or use our contact page.
Want to pass your MOT first time?
Message us on WhatsApp with your reg and postcode, or use our contact form, for a price before any work starts.
WhatsApp for a free quote Call 07563 350335 Contact form
Labour £30 to £50 per hour depending on the job. Send your reg number and we will reply with a price before any work starts.
Frequently asked questions
What is the legal tyre tread depth in the UK?
For cars it is 1.6mm across the central three-quarters of the tread, around the entire circumference of the tyre. Each tyre below the limit can bring a fine of up to £2,500 and three penalty points.
Is the 20p test accurate?
It is a good quick guide. If the outer band of a 20p coin is visible when it is placed in the main grooves, the tread may be close to or below the legal limit and should be measured properly with a gauge.
What tread depth should I change tyres at for winter?
Many tyre makers and road safety groups suggest considering replacement at around 3mm, because wet grip falls away noticeably below that. It is advice rather than law, but it makes a real difference on cold, wet roads.
Do you fit tyres?
We check tread depth, condition and pressures as part of our visits and pre-MOT checks. For tyre fitting, message us your reg and we will tell you whether it is something we can arrange or point you in the right direction.
