When to Replace
When to Replace Your Tyres: UK Tread Depth Law, Safety, and Costs (2026)
The legal requirements, the safety data, and the real costs of getting it wrong. Everything you need to know about when your tyres need replacing.
The Legal Minimum: 1.6mm
UK law requires a minimum tread depth of 1.6mm across the central three-quarters of the tyre width, around the full circumference. This applies to all cars, vans, and trailers.
Fine per tyre
Up to £2,500
Points per tyre
3 points
All 4 illegal
£10,000 + ban
Four illegal tyres means 12 penalty points, which is an automatic driving ban. Plus fines of up to £10,000 in total. The cost of replacing four tyres is a fraction of this.
The 20p Test
The simplest way to check your tread depth at home:
- Take a 20p coin and insert it into the main tread grooves of your tyre.
- If you can see the outer band of the coin, your tread is below the legal minimum of 1.6mm.
- Check in several places across the tyre width and around the circumference.
- If the outer band is visible at any point, the tyre needs replacing immediately.
For a more accurate reading, buy a tread depth gauge (£3-5 from Halfords or Amazon). Digital gauges give readings to 0.1mm accuracy.
3mm vs 1.6mm: The Safety Case
While 1.6mm is the legal minimum, most tyre experts, the RAC, and the AA recommend replacing at 3mm. The performance difference is not gradual; it drops off sharply below 3mm.
| Tread Depth | Wet Braking (50mph) | Extra Distance vs 8mm | Risk Level |
|---|---|---|---|
| 8mm (new) | 25.5m | Baseline | Optimal |
| 5mm | 28.2m | +2.7m | Good |
| 3mm | 32.0m | +6.5m | Replace soon |
| 1.6mm (legal min) | 40.2m | +14.7m | Dangerous |
At 1.6mm, a car travelling at 50mph in the wet takes nearly 15 metres longer to stop than with new tyres. That is roughly four car lengths. From 3mm to 1.6mm alone, the difference is over 8 metres. In real driving, this is the difference between stopping safely and hitting the vehicle in front.
How Long Do Tyres Last?
| Tier | Typical Mileage | Years (10k mi/yr) | Factors |
|---|---|---|---|
| Budget | 15,000-20,000 mi | 1.5-2 years | Faster wear in wet. Front tyres wear faster on FWD cars. |
| Mid-Range | 25,000-35,000 mi | 2.5-3.5 years | Best value for most drivers. Consistent wear. |
| Premium | 35,000-50,000 mi | 3.5-5 years | Longest-lasting. Michelin typically leads. |
What Affects Tyre Lifespan?
- Driving style: Aggressive acceleration, hard braking, and fast cornering wear tyres significantly faster.
- Tyre pressure: Under-inflated tyres wear the edges faster. Over-inflated tyres wear the centre. Check monthly.
- Wheel alignment: Misalignment causes uneven wear, potentially halving tyre life.
- Road conditions: Potholes, rough surfaces, and speed bumps accelerate wear.
- Front vs rear: Front tyres on front-wheel-drive cars wear 2x faster. Rotate every 6,000 miles.
- Age: Even if tread is fine, replace tyres older than 6 years. Rubber degrades with age.
Signs You Need New Tyres
Tread wear indicators visible
Moulded rubber bars at 1.6mm between the main grooves. When the tread is level with these bars, the tyre is at or below legal minimum.
Replace immediately
Uneven wear patterns
Wear on one edge suggests alignment issues. Wear in the centre means over-inflation. Wear on both edges means under-inflation.
Get alignment checked, then replace
Cracks in the sidewall
Fine cracks in the sidewall rubber indicate age degradation. The tyre structure may be weakened even if tread looks fine.
Replace soon
Bulges or blisters
A bulge in the sidewall indicates internal structural damage. The tyre could blow out without warning.
Replace immediately
Vibration at speed
Steering wheel vibration at motorway speed can indicate a tyre defect, balance issue, or separation. Get checked.
Get checked immediately
Slow punctures
If you need to top up pressure more than once a month, you may have a slow puncture from a nail or valve issue.
Repair or replace
Puncture Repair vs Replacement
Repair Is Possible If...
- Puncture is in the central tread area (not the sidewall)
- Hole is less than 6mm in diameter
- Tread depth is still above 1.6mm (ideally 3mm+)
- There is no sidewall damage
- The tyre has not been driven flat (destroys the internal structure)
Cost: £20-45 | Time: 30 minutes
Replacement Is Needed If...
- Puncture is in the sidewall or shoulder area
- Hole is larger than 6mm
- Tyre has been driven flat (even a short distance)
- There is any sidewall damage or bulging
- It is a run-flat tyre (most cannot be repaired)
- Tread depth is near the legal minimum
Cost: £70-200+ | Time: 30-60 minutes
MOT and Tyres
Tyres are checked as part of every MOT test. Common tyre-related failure reasons include:
- Tread below 1.6mm: The most common tyre-related MOT failure.
- Cuts, bulges, or cords showing: Any structural damage is an immediate failure.
- Wrong size or type: Different sizes on the same axle, or a type not suitable for the vehicle.
- Incorrectly seated on the rim: Tyre not properly fitted.
A tyre-related MOT failure means you cannot legally drive the car until the issue is fixed. You will need to pay for new tyres plus the re-test. It is much cheaper to check your tyres before the MOT and replace any that are borderline.