UK tyre safety 20p test: how to avoid a £2,500 fine

The short answer: UK tyre safety and the 20p test

The UK tyre safety 20p test is a quick way to check whether your tread is close to the legal minimum of 1.6mm. You place a 20p coin into the main grooves of the tyre. If the outer band of the coin is still visible, the tread may be below the legal limit and the tyre should be inspected by a professional.

The stakes are high. Wales Online reported that drivers caught with tyres below 1.6mm face a fine of up to £2,500 and penalty points that can cost them their licence. The RAC says the £2,500 fine and three penalty points apply to each tyre, so a car with several bad tyres can be hit far harder.

The check is easy to skip. A poll of 2,000 motorists by OnePoll.com for Halfords, released during Tyre Safety Month, found that 64% did not know about the 1.6mm legal tread limit. Nearly four in 10 (38%) did not know about the 20p trick, and almost a third (30%) were unaware of the size of the fine they could face.

How the 20p test works and the tyre tread depth legal limit in the UK

The legal minimum depends on the vehicle, but for cars, caravans and vans the tread must be “at least 1.6 mm”, according to the Express. That depth has to be met across a continuous band around the full circumference of the tyre. Because the limit applies all the way round, it makes sense to test more than one spot on each tyre rather than relying on a single reading.

Wales Online says the border of a 20p coin is slightly larger than the legal limit, which is why it works as a rough guide. The RAC describes the method this way: “Just take a 20p coin and insert it into the tread grooves on the tyre. If you can’t see the outer band on the coin, your tyres are above the legal limit.” If the band is visible, the RAC says, “your tyres could be unsafe and require professional inspection by a mechanic”.

The coin is a guide rather than a precise measurement. The Express reports that a tread depth gauge can be bought cheaply, often for under £10, and gives a more exact reading. Comedian Judi Love, who fronted a Halfords video on the check, said it “takes less than 30 seconds to check all four tyres”.

Many safety bodies recommend replacing tyres before they reach the legal limit, with 3mm often cited as a safer point to act, according to the Express report. The RAC points to tests by the technical organisation MIRA, which found that stopping distances increase dramatically once tyres are below 3mm. It said the difference in wet braking distance between a tyre worn to 3mm and one worn to 1.6mm “can be as much as 44%”.

As an illustration only, and not a measured figure: if a car on 3mm tread needed 50 metres to stop in the wet, a 44% longer distance would be 72 metres. That is a gap of 22 metres, roughly the length of several parked cars, and it is the margin between stopping and not stopping.

What illegal tyres can cost: the £2,500 fine in detail

The sources describe the penalty slightly differently, so it helps to read them carefully. Wales Online reported a fine of up to £2,500 and up to 12 penalty points. The RAC says driving with bald tyres “can risk a fine of £2,500 and three penalty points – and that’s per tyre”. The Bradford Telegraph and Argus, citing GM Rides, likewise reported court fines of up to £2,500 per illegal tyre alongside penalty points.

On the RAC’s per-tyre basis, the maximum exposure builds quickly. The table below applies that basis. The one-tyre and four-tyre rows match the figures given by the RAC and Wales Online; the two and three-tyre rows are our own arithmetic, and the amounts are maximums rather than what a court will necessarily impose.

The RAC said that if all four tyres are worn below the legal limit, a driver “could potentially be summoned to court, lose your licence and face a £10,000 fine”. Wales Online added that the penalty could be more severe for new drivers, because two worn tyres is the equivalent of six points, “enough to lose their permit”.

The poll suggests younger drivers are the least prepared. While 38% of all motorists did not know the 20p trick, the figure rose to 59% among younger drivers, according to Wales Online.

MOT tyre requirements and the 2mm question

Tyres are part of the annual test. A report in the Daily Express listing what an MOT covers includes “tyres – including tread depth and condition of the tyres”. The test usually lasts 45 minutes to an hour, according to an RAC motoring expert quoted in that report, and longer if repairs are needed afterwards.

A vehicle with a “major” or “dangerous” result fails. GOV.UK, quoted by the Express, says drivers “can be fined up to £2,500, be banned from driving and get 3 penalty points for driving a vehicle that has failed its MOT because of a ‘dangerous’ problem”. You can only take the vehicle away if your current MOT is still valid and no dangerous problems were listed. Otherwise it must be repaired first.

So will 2mm on a tyre pass? None of the sources gives a separate MOT measurement or mentions 2mm. The only legal figure they cite is 1.6mm, and 2mm is 0.4mm above it. On those figures a tyre at 2mm is above the legal minimum, but it is much closer to the limit than the 3mm point that safety bodies suggest, and the MOT also looks at the condition of the tyre as well as its depth. For the test’s own rules, check GOV.UK or ask the garage.

Tyres are not the most common reason for failure. The RAC says the three most common causes are suspension, brakes, and lights and signals, which is a reminder that a good tyre check does not mean the whole car will pass.

Pressure, condition and other tyre safety checks: what you need to know

Tread depth is only part of the picture. Steve Brown, divisional manager at Just Tyres, told the Express: “Most drivers know that tyres need at least 1.6mm of tread. But tread depth isn’t the only thing that matters.” He warned that a tyre 6 to 8 PSI below its recommended pressure “can look completely normal”, particularly on modern cars with wide, low-profile tyres.

The Express reported that, under the Construction and Use Regulations, owners must keep tyres inflated enough for the road, and linked this to the same £2,500 fine risk. Just Tyres advises checking all four tyres when cold and using the pressure the manufacturer recommends. You will usually find it on a sticker inside the driver’s door frame, inside the fuel flap or in the handbook.

Pressure also affects running costs. The Express reported that a tyre 20% under-inflated can increase fuel consumption by as much as 2%, while National Tyres and Autocare said over-inflated tyres can reduce grip and cause uneven wear. Previous National Highways research suggests only one in six drivers check their tyres before a long journey.

Wet roads raise the stakes. According to the Highway Code, as cited by GM Rides, stopping distances in wet conditions are at least double those in the dry. Majid Ismailzada of GM Rides said: “Checking your tyres before you set off is far better than discovering a problem when you need to stop.” GM Rides also advised looking for cuts, cracks or bulges.

Key dates and what happens next

The advice arrives as the weather turns. The Express reported that wetter roads and falling temperatures from October onwards make worn tyres more likely to struggle with surface water, raising the risk of aquaplaning. The RAC recommends a quick check at home every couple of weeks and before longer trips.

A sensible routine for the coming weeks follows from the sources. Do a coin check on all four tyres before your next long journey, which takes under a minute. Check pressures when the tyres are cold, using the figure on the door frame sticker. If the coin’s outer band is visible, or you see damage, book an inspection; the Express reported that many garages offer free tyre safety checks.

The MOT has its own calendar. A vehicle needs its first test by the third anniversary of its registration, then each year by the anniversary of its last MOT, according to the Daily Express summary of GOV.UK rules. Driving without a valid MOT can bring a fine of up to £1,000, with exceptions only for driving to a pre-arranged test or to a place of repair.

Halfords has produced a limited number of 20p key chains for drivers who do not carry coins, after its poll found 48% of motorists had none to hand. Karen Bellairs, the retailer’s chief customer officer, said: “You don’t have to be a car expert to check them.”

Your questions answered

What is the fine for illegal tyres in the UK?

The sources say up to £2,500. The RAC says that figure, with three penalty points, applies per tyre, and that four tyres below the limit could mean a £10,000 fine, a court summons and loss of licence. Wales Online reported up to 12 penalty points. These are maximums, and the outcome depends on the court.

What is the 20p rule on tyres?

It is a rough check of tread depth. Insert a 20p coin into the main tread grooves; if the outer band of the coin is hidden, the RAC says your tyres are above the legal limit. If the band is visible, the tread may be too low and a mechanic should inspect the tyre. A tread depth gauge is more precise.

Will 2mm on tyres pass MOT?

The sources do not give an MOT-specific figure or mention 2mm. They cite a legal minimum of 1.6mm, and 2mm is above that. The MOT inspects both tread depth and tyre condition, and safety bodies suggest acting at 3mm, so a tyre at 2mm is legal on these figures but close to the point where wet braking worsens. Check GOV.UK for the test’s own requirements.