A tyre can look perfectly acceptable from the driveway and still have too little grip for a wet A-road, an emergency stop or an MOT. Knowing how to check tyre tread takes only a few minutes, needs very little equipment, and gives you a clearer picture of whether your car is safe and road legal.
For most drivers, a monthly check is a sensible habit, particularly before a long journey, winter driving or your MOT. Look at all four tyres, not just the one that appears most worn. Tyres can wear at different rates depending on your vehicle’s alignment, tyre pressures, suspension condition and driving style.
How to check tyre tread with a 20p coin
The quickest home check uses an ordinary 20p coin. Park on level ground, apply the handbrake and turn the steering wheel so you can clearly see the front tyre tread. If you have just driven, allow the tyres to cool before inspecting them.
Insert the 20p coin into the main tread groove. The outer rim of the coin measures roughly 3mm. If the outer rim is hidden by the tread, you have more than approximately 3mm remaining in that groove. If you can see the outer rim, your tread may be at or below 3mm and should be measured properly soon.
Repeat the test in several places across each tyre: near the inner edge, centre and outer edge, then at different points around the circumference. A tyre may have adequate tread in one area but be worn close to the legal limit elsewhere.
The 20p test is useful as an early warning, not a precise legal measurement. It cannot confirm that a tyre meets every roadworthiness requirement, especially if wear is uneven or damage is present.
What is the legal minimum tyre tread depth?
For cars, vans and most light vehicles in the UK, the legal minimum is 1.6mm of tread across the central three-quarters of the tyre’s width, around its complete circumference. Falling below this limit makes the tyre illegal and unsafe.
Waiting until 1.6mm is not always the best decision. Wet-weather performance reduces as grooves become shallower because there is less space to clear water from beneath the tyre. Many garages recommend considering replacement at around 3mm, particularly if you regularly travel at motorway speeds, carry children, drive a heavier vehicle or cover significant mileage in wet conditions.
The right time to replace a tyre can depend on its type and use. A vehicle used mainly for short local trips may show different wear from a high-mileage commuter car. Electric and hybrid vehicles can also place greater demands on tyres because of vehicle weight and instant torque. The legal limit remains the same, but earlier replacement can provide greater confidence in poor weather.
Check the tread wear indicators too
Most modern tyres have tread wear indicators moulded into the main grooves. These are small raised bars set at the legal minimum tread depth. Their position is often marked by a triangle, the letters TWI, or another symbol on the tyre sidewall.
When the surrounding tread is level with these raised bars, the tyre is at 1.6mm and must be replaced. Check several indicators around the tyre rather than relying on a single one. A tyre can wear more heavily on one section due to braking, cornering or a mechanical issue.
Use a tyre tread depth gauge for an accurate reading
A simple tread depth gauge is the most reliable tool for checking your tyres at home. It gives a reading in millimetres and removes the uncertainty of judging a coin test by eye.
Place the gauge’s probe into a main tread groove, keeping it straight and firmly seated at the bottom of the groove. Take readings from the inner, centre and outer sections of the tyre. Record the lowest result from each tyre, then repeat around the tyre’s circumference.
If the readings differ noticeably across the width, the problem may be more than ordinary tyre wear. It could point to incorrect tyre pressure, wheel alignment issues, worn suspension components or an imbalance. Replacing a tyre without identifying the cause can mean the new tyre wears prematurely too.
Uneven tyre wear: what the pattern can tell you
Tread depth matters, but the wear pattern matters as well. An even tyre should wear gradually across its surface. Uneven wear is often your vehicle asking for attention.
Wear on both outer edges commonly suggests the tyre has been driven underinflated. Low pressure allows the shoulders of the tyre to carry more of the load, increases heat build-up and can affect fuel economy. Wear concentrated in the centre may indicate overinflation, where the middle of the tyre carries too much of the contact load.
If one edge is noticeably more worn than the other, wheel alignment is a likely cause. Potholes, kerb impacts and worn steering or suspension parts can alter alignment. A steering wheel that sits off-centre, a vehicle that pulls to one side or tyres that squeal more than usual when cornering are further signs worth investigating.
Patchy or cupped areas around the tread can be associated with wheel balancing problems, worn shock absorbers or suspension wear. These faults can affect handling and braking as well as tyre life, so it is wise to have the vehicle inspected rather than simply fitting another tyre.
Look beyond tread depth
A tyre can have plenty of tread left and still be unsuitable for the road. During your check, inspect the sidewalls and tread surface for cuts, cracks, bulges, embedded objects and exposed cords. A bulge can indicate internal structural damage, often after striking a pothole or kerb, and requires urgent professional advice.
Also check tyre pressures against the vehicle manufacturer’s recommended figures. You will usually find them in the handbook, fuel filler flap or driver’s door frame. Check pressures when tyres are cold, including the spare wheel if your vehicle has one. Correct pressures help tyres wear evenly and support predictable braking and handling.
Do not forget to look for objects lodged in the tread. A screw may not cause an immediate flat tyre, but it can lead to a slow puncture. Avoid pulling it out at home. Leaving it in place may help the tyre retain air until it can be assessed safely.
Are cracks in tyre tread always an MOT failure?
Not every small surface mark means a tyre will fail an MOT, but cracks, cuts or splits deep enough to expose internal structure are serious. Likewise, a tyre that is distorted, has a bulge, or has tread below the legal limit will not pass.
An MOT is a snapshot of roadworthiness on the day. It is not a substitute for regular checks between tests. A tyre may be legal at its MOT and become unsafe months later, particularly if mileage is high or the vehicle develops an alignment issue.
How often should you inspect your tyres?
A monthly visual and tread check is a practical routine for most vehicles. Check again before a holiday, a long motorway journey, towing, carrying a heavy load or travelling during colder, wetter months. If you notice a warning light, repeated pressure loss, vibration through the steering wheel or a change in how the car handles, inspect the tyres straight away.
Drivers who cover high mileage, use performance vehicles or drive electric vehicles may benefit from more frequent checks. These vehicles can wear tyres faster depending on tyre compound, torque delivery and driving conditions. There is no single interval that fits every car, but regular checks are far less expensive than discovering a problem after a puncture or an MOT failure.
When to arrange a professional tyre inspection
Arrange an inspection if your 20p test shows visible coin rim, a tread gauge reading approaches 3mm, or the wear is uneven. Professional assessment is also the right choice for sidewall damage, persistent pressure loss, vibration, pulling to one side or a suspected puncture.
At AutoNet VIP, a tyre inspection can identify whether you simply need replacement tyres or whether wheel alignment, balancing, brakes or suspension should be checked at the same time. Clear measurements and straightforward advice make it easier to decide what work is genuinely needed.
Tyres are the only part of your vehicle that touches the road. A few minutes spent checking them today can protect your stopping distance, your MOT result and the people travelling with you tomorrow.
