Here at Cars for beginners, we believe in a safety-first approach, and nothing says safety like the correct tyre tread depth. The tread on your tyres isn’t just there for looks – it’s a crucial safety feature. Those grooves and channels carved into the rubber are designed to maintain grip by channelling water away from the tyre’s surface, helping to prevent aquaplaning. They also provide traction when braking, accelerating, and cornering, especially in wet or slippery conditions.
As you drive, the tread wears down gradually, which means its ability to do all of this reduces over time. That’s why keeping an eye on tread depth is one of the simplest yet most important checks any driver can do.
Tyre tread depth - in short
Legal limit: Tyre tread depth in the UK must be at least 1.6mm across the central three-quarters of the tyre’s width, around the full circumference.
New tyres: Usually start with around 8mm of tread. Many experts recommend replacing tyres once tread reaches 3mm for safety.
Why it matters: Adequate tread improves grip, reduces braking distances, and helps prevent aquaplaning. Low tread increases accident risk, MOT failures, fines, and insurance issues.
Checking tread depth: Use the 20p coin test, a tread depth gauge, or look for tread wear indicators built into the tyre.
How often to check: Inspect tyres at least once a month, and before long journeys. Quick checks every couple of weeks are even better.
What affects tread wear: Driving style, tyre pressure, wheel alignment, road conditions, tyre type, and load/speed all influence how fast tread wears down.
When to replace: Don’t wait until 1.6mm – replacing at 3mm or sooner provides a safer margin, especially in wet conditions.
The legal minimum tread depth in the UK
In the UK, the law is clear: tyres must have at least 1.6mm of tread depth across the central three-quarters of the tyre’s width, and this must be consistent all the way around the tyre’s circumference. If any of your tyres fall below this limit, they’re classed as illegal.
Driving on tyres below the legal limit can result in fines of up to £2,500 per tyre and three penalty points. If more than one tyre is affected, those penalties stack up quickly. It’s not just about avoiding fines, though – tyres with insufficient tread can significantly compromise your safety, particularly in wet conditions where grip is already reduced.
How much tread do new tyres have?
Most brand-new tyres start out with around 8mm of tread, although this can vary depending on the design and purpose of the tyre. Winter tyres, for example, often come with slightly deeper grooves to cope better with snow and slush.
While 1.6mm is the legal minimum, many motoring organisations recommend replacing tyres once they reach around 3mm. This is because braking distances increase sharply once tread drops below this level, especially on wet roads. Think of 3mm as the safety buffer, not the finish line.
How often should you check tread depth?
You don’t need to be a mechanic to keep on top of tyre checks. A good rule of thumb is to inspect your tyres every couple of weeks, or at least once a month if that’s more realistic for you. It’s also worth taking a closer look before any long journeys. We have a handy car maintenance guide set out, for you to follow if you need it – as tyre check should be a part of routine checks.
There are several ways to measure tread depth. The easiest is the 20p coin test: place a 20p coin into one of the main grooves. If the outer band of the coin is visible, your tread could be too low and should be checked more carefully with a proper tread depth gauge. Many tyres also have tread wear indicators – small raised sections inside the grooves – which become flush with the tread when it’s close to the legal limit.
What affects how quickly tread wears down?
Not all tyres wear at the same rate. The lifespan of your tread depends on a mix of driving habits, road conditions, and tyre maintenance. Hard cornering, heavy braking, and rapid acceleration will all eat away at tread more quickly. Road surfaces matter too: rough or potholed roads can accelerate wear compared to smooth tarmac.
Tyre pressure is another big factor. Under-inflated tyres tend to wear more on the edges, while over-inflated ones wear in the centre. Both scenarios reduce the tyre’s lifespan and compromise performance. Issues like poor wheel alignment or suspension problems can also cause uneven wear across the tyre, which is why it’s important to get these checked if you notice your tyres wearing down more on one side.
Even the tyres themselves play a part. Premium brands often use harder-wearing compounds, while softer tyres (like winter or performance models) may sacrifice longevity for grip. Driving in hot weather, carrying heavy loads, or spending long stretches at motorway speeds can also speed up the process.
Why low tread depth is dangerous
Once tread depth drops below safe levels, the tyre’s ability to perform its most vital job – keeping you in control – is severely reduced. With shallower grooves, tyres can’t disperse water as effectively, which raises the risk of aquaplaning. Stopping distances also increase dramatically in the wet, which could mean the difference between a near miss and a collision.
Low tread doesn’t just affect wet grip. Handling and cornering stability also suffer, and the tyre itself becomes more vulnerable to punctures or blowouts. On top of this, tyres below the legal limit will fail an MOT test, and as mentioned earlier, can lead to hefty fines and penalty points if you’re caught driving with them. Insurance companies may even refuse to pay out after an accident if your tyres are found to be illegal.
When should you replace your tyres?
Although the law allows you to drive on tyres down to 1.6mm, it’s wise to act sooner. Replacing tyres at around 3mm gives you a much greater margin of safety, particularly if you regularly drive in wet or wintry conditions. Regular checks, proper inflation, and wheel alignment can all help extend tyre life, but no tyre lasts forever.
If you notice uneven wear, vibration, or cracks in the rubber, don’t ignore them – these are signs your tyres may need replacing regardless of tread depth. Investing in new tyres before you absolutely have to is far cheaper than the potential cost of an accident or fine.
Final word
Tyre tread depth might not be the most exciting aspect of car maintenance, but it’s one of the most important. Keeping tyres above the legal limit – and ideally above 3mm – ensures you get the grip, handling, and stopping power you need, particularly in the wet. Checking them regularly takes only a few minutes, and could save you from far more serious consequences down the line.
