Tyre Tread Depth: UK Legal Limits & When to Replace

Every car tyre in the UK must have a minimum tread depth of 1.6mm across the central three-quarters of the tread, around the full circumference of the tyre. Drive below that limit and you face a fine of up to £2,500 and three penalty points — per tyre. With four tyres, that’s potentially £10,000 and 12 points, enough to lose your licence on the spot.

But the legal minimum isn’t the same as the safe minimum. Here’s the full picture.

The 20p Test: Checking Your Tread at Home

The simplest way to check whether your tyres are close to the legal limit is the 20p test. Take a 20p coin and insert it into the tread grooves across the tyre. If the outer band of the coin is hidden, your tread is above 3mm — you’re fine. If you can see the band, your tread is getting low and you should get a professional check. This works because the outer rim of a 20p coin is approximately 1.6–2mm wide.

Why 3mm Is the Real Safety Threshold

Testing by TyreSafe and independent motoring organisations consistently shows that tyres with 3mm of tread stop significantly shorter in wet conditions than tyres worn to the 1.6mm legal limit. At 50 mph on a wet road, the stopping distance difference between 3mm and 1.6mm can be up to 8 metres — roughly two car lengths.

Tread grooves channel water away from the contact patch between the tyre and the road. As grooves wear, they become less efficient at clearing water, especially at speed. This is why wet-weather braking performance degrades sharply as tread approaches the legal minimum, not at a linear rate.

Tread Wear Indicators: What Are They?

All tyres have built-in tread wear indicators (TWIs) — small rubber bars set at 1.6mm depth in the base of the main tread grooves. When the tyre surface wears level with these bars, the tyre has reached the legal minimum and must be replaced. You can usually find TWIs by looking for small arrows or ‘TWI’ markings on the tyre sidewall, which point to where the indicator bars are located.

How Quickly Do Tyres Wear?

Tyre wear rate depends on several factors: driving style, vehicle weight, road surface, and whether your wheel alignment is correct. As a rough guide, most car tyres start with 7–8mm of tread when new. Under normal mixed driving conditions in Bradford, you might expect to lose around 1.5–2mm per 10,000 miles on the front axle of a front-wheel-drive car.

• Front tyres on a FWD car typically wear 30–50% faster than rears, as they handle both steering and drive forces
• Uneven tyre wear (worn on one edge, worn in the centre, or scalloped) indicates alignment, pressure, or suspension issues and warrants investigation
• Regular rotation (swapping front and rear tyres every 5,000–8,000 miles) evens out wear and extends tyre life

Uneven Tyre Wear: What the Patterns Mean

Different wear patterns tell you different things about your vehicle’s condition:

• Worn across the full width: Normal wear if even — suggests the tyre is approaching end of life uniformly
• Worn on outer edges only: Consistent underinflation — the tyre is running too soft and the shoulders take the load
• Worn in the centre only: Consistent overinflation — the tyre is too hard and only the centre contacts the road
• Worn on one edge only: Wheel alignment or camber issue — get a 4-wheel alignment check
• Scalloped or cupped wear: Worn shock absorbers or suspension components — get the suspension checked

What Does a Tyre Replacement Cost in Bradford?

Budget tyres in common sizes (e.g. 205/55 R16) start from around £45–60 fitted at Pro Flo. Mid-range tyres typically fall in the £70–100 range fitted, and premium tyres from Michelin or Continental are typically £100–160+ fitted, depending on size. We’ll always give you honest options across price tiers without pressure — come and see us at 365 Canal Road.