Most drivers check their tyre pressure occasionally and assume the rest takes care of itself. In practice, a single tyre running below the legal tread depth can attract a fine of up to £2,500 and three penalty points per tyre. On a car with four illegal tyres, that adds up to £10,000 and twelve points: an automatic driving ban for most full licence holders. More damaging still, illegal tyres give your insurance company a contractual basis to reduce or refuse a claim, leaving you personally responsible for damage and injuries that can run into tens of thousands of pounds. This guide covers exactly what UK tyre law requires, how to check your tyres properly at home, what happens when police or an insurer find a problem, and what the evidence actually says about when a tyre should be replaced, not merely when the law forces you to replace it.
What the Law Actually Requires
The legal framework for tyre standards in the UK is the Road Vehicles (Construction and Use) Regulations 1986, specifically Regulations 26 and 27. These set out three distinct requirements that every tyre on a car must meet simultaneously. Failing on any one of them is an offence, regardless of whether the others are satisfied.
The 1.6mm tread depth rule
A car tyre must have a tread depth of at least 1.6mm across the central three-quarters of its breadth, measured around the entire circumference of the tyre. The phrase "central three-quarters" is precise: the outer edge of the tread, roughly one-eighth of the tread width on each side, is excluded from the measurement. However, the required depth must be present continuously all the way around the circumference. A single worn patch anywhere on the tyre makes it illegal, even if the rest of the tread is well above the limit.
This standard applies to cars and light goods vehicles up to 3,500kg. Motorcycles over 50cc have a separate requirement of at least 1mm in a continuous band around the central three-quarters of the tread, with the remainder of the tread visible. If you ride as well as drive, our motorcycle guide covers the rules specific to two-wheelers.
Tyre pressure
There is no single legal pressure figure. The regulations require that tyres are inflated to the pressure specified by the vehicle manufacturer for the load being carried. You will find this on a sticker inside the driver's door jamb or on the fuel filler flap, and in the owner's handbook. Running significantly under-inflated tyres causes uneven wear, overheating and increased stopping distances. Over-inflated tyres reduce the contact patch with the road and increase the risk of a blowout. Either condition can make a tyre unfit for use under the regulations and can become a point of dispute in an insurance claim following an accident.
Tyre condition
Beyond depth and pressure, the regulations require that a tyre must not have any lump, bulge or tear that exposes the cord or ply structure beneath the rubber. A bulge in the sidewall indicates internal structural damage, typically caused by impact with a pothole or kerb. Such a tyre can fail suddenly at speed. Driving on one is an offence in its own right, independent of tread depth. Any cut or tear that exposes the cord, or that is longer than 25mm or deeper than 10% of the tyre's cross-section width, is also a clear failure.
Mixing tyre construction types
Regulation 26 of the same legislation makes it illegal to mix radial-ply and cross-ply tyres on the same axle. Almost every modern passenger car tyre is radial-ply, so this rarely arises in practice. The situation where it can occur is when a full-size spare from a different vehicle is pressed into service. It is worth checking the sidewall markings if you ever swap in an unfamiliar spare. Mixing different brands or tread patterns on the same axle is not illegal, but is genuinely inadvisable because it creates inconsistent braking and handling balance, particularly in an emergency.
How to Check Your Tyres at Home
A thorough tyre check takes about five minutes and requires only a 20p coin, a tyre pressure gauge available from any petrol station or supermarket, and your attention. The RAC and AA both recommend checking tyres at least monthly and before any long journey. The process is straightforward once you know what to look for.
The 20p coin test
Insert a 20p coin into one of the main tread grooves. The outer band of a 20p coin is approximately 2 to 3mm wide. If that outer band is clearly visible above the tread surface when the coin is seated in the groove, your tread is getting low and you should measure it precisely with a gauge. If the band disappears into the groove, your tread is likely above 2mm. This is a prompt, not a precise measurement. Test several grooves across the tyre width and at multiple points around the circumference: wear is rarely perfectly uniform. Tyres often wear faster on the edges if they are under-inflated, or in the centre if over-inflated, which reflects the pressure history of that tyre.
Tread wear indicators
Since the mid-1990s, all passenger car tyres manufactured for the European market have been required to include tread wear indicators (TWIs). These are small rubber bars moulded into the bottom of the main tread grooves at exactly 1.6mm. When the tread surface wears down to the level of these bars, the tyre is at the legal limit and must be replaced. You can locate the TWIs by looking for a small triangle or the letters "TWI" on the tyre sidewall: these marks indicate which section of the circumference the wear bars are positioned in. If the tread surface is level with the bars at any point, the tyre has reached the end of its legal life.
For a definitive measurement rather than an indication, a tread depth gauge gives an exact reading. They are sold in most motor accessory shops and online for £5 to £15. Using one takes seconds and removes any uncertainty about whether a tyre is legal or borderline.
Checking tyre pressure correctly
Always measure tyre pressure when the tyres are cold. Cold means the car has been parked for at least two hours, or driven fewer than two miles at low speed. Driving heats the air inside the tyre, raising pressure and giving a false reading. Use the manufacturer's recommended pressures, not the maximum pressure figure printed on the tyre sidewall: that figure is the maximum the tyre can safely contain, not the target operating pressure. Check all four tyres and the spare if you carry one. Pressures for a loaded car (passengers and luggage) are usually higher than for solo driving: the door sticker typically shows both figures.
Sidewalls and tyre age
Examine each sidewall visually for bulges, cuts, craze cracking or embedded objects. Craze cracking, a network of fine surface cracks, can indicate that the rubber compound is degrading with age rather than wear. Any bulge, however small, should be inspected by a tyre technician before further driving.
The manufacturing date of a tyre is encoded in the DOT code on the sidewall. After the letters "DOT" you will find a series of alphanumeric characters. The last four digits are the ones that matter: the first two represent the week of manufacture and the second two the year. A code ending in "3519" means the tyre was made in the 35th week of 2019. There is no UK law setting a maximum tyre age, but TyreSafe and the British Tyre Manufacturers' Association both recommend professional inspection once a tyre is five years old, and replacement at ten years regardless of visual condition. Rubber compounds degrade over time even on a tyre that has been stored or used lightly. When buying a used car, reading the DOT codes on all four tyres takes thirty seconds and can reveal tyres that look fine but are past a safe working life.
The Fines and Penalty Points for Illegal Tyres
Tyre offences sit in the same legal category as dangerous mechanical defects, and the penalties reflect that. They are not fixed at the maximum level in every case, but understanding the full scale of the possible consequences is important.
The scale of the penalty
Under Regulation 27 of the Construction and Use Regulations, each tyre that fails to meet the legal standard can attract a maximum penalty of a £2,500 fine and three penalty points. That is per tyre. A car with four illegal tyres could in theory face £10,000 in fines and twelve penalty points. Twelve points triggers the totting-up procedure and automatic disqualification for most full licence holders. The threshold is lower for drivers who qualified less than two years ago: six penalty points causes the licence to be revoked automatically, requiring the driver to retake the theory and practical tests before they can drive again.
How tyre offences are enforced
Police can check tyre condition during any roadside stop, including routine checks and stops following minor moving offences. Tyre inspection is also routine following any road traffic collision, including low-speed incidents. The outcome of a police check can take several forms. An officer may issue a Vehicle Defect Rectification Scheme notice, giving the driver 14 days to repair the defect and produce proof of the repair to a police station. They may issue a Fixed Penalty Notice carrying a lower fine and the penalty points. In more serious cases, where the defect is extreme or where it is connected to a collision, a prosecution summons leads to a court appearance where the maximum penalties apply. The worst outcomes consistently arise when illegal tyre condition is linked to an accident, at which point tyre inspection is part of the full collision investigation.
How Illegal Tyres Affect Your Car Insurance
The financial consequences of an insurance dispute following an accident on illegal tyres can dwarf the direct penalty. Understanding the mechanism by which this happens is essential for any driver who has ever been tempted to delay tyre replacement until the MOT forces the issue.
The roadworthiness condition in your policy
Every UK car insurance policy is a contract. Almost all of them contain a condition requiring the insured vehicle to be maintained in a roadworthy and legal condition. This condition is sometimes expressed explicitly as a roadworthiness clause, sometimes as an exclusion for use of the vehicle in an unlawful state, and sometimes as a general condition of cover. Tyres are fundamental to roadworthiness. When an accident occurs and the vehicle is found to have an illegal tyre, the insurer does not necessarily need to demonstrate that the tyre caused the accident. The breach of the policy condition can be sufficient grounds to reduce or refuse the policyholder's own-damage claim, regardless of how the collision occurred.
What happens after a collision
Following any significant accident, an insurer will typically arrange for a vehicle examiner to inspect the car before authorising repair. Tyre tread depth and condition are measured as a standard part of that inspection. If a tyre is found below 1.6mm or structurally compromised, the finding is recorded in the examiner's report and flagged to the claims handler. The claims handler then assesses whether the policy condition has been breached and what the implications are for the claim. Outcomes depend on the specific policy wording and the circumstances of the accident, but refusal or reduction of the own-damage payout is a realistic possibility, not a theoretical one.
Third-party liability and subrogation
The situation for third-party claims works differently. Under the Road Traffic Act 1988, insurers are legally required to satisfy valid third-party claims even when the policyholder was in breach of their policy. An innocent third party will not be left uncompensated because the at-fault driver had illegal tyres. However, once the insurer has paid the third-party claim, they have the legal right to pursue the policyholder to recover that payment. This is called subrogation. In a serious accident involving injuries or a written-off vehicle, third-party costs can be very large. A driver who delayed replacing a £60 tyre may find themselves personally liable for a sum many times that figure.
Practical steps to protect your position
- Keep a simple record of tyre checks. A dated photograph of a tread depth gauge reading stored on your phone costs nothing and constitutes evidence that you were monitoring your tyres.
- If a garage includes a tyre advisory in a service report, act on it promptly. An unaddressed advisory creates a paper trail that an insurer can use to argue you had notice of the problem.
- If you buy secondhand tyres, ask for documentation that confirms they meet legal standards and are of a known age.
- Notify your insurer before fitting tyres that differ significantly from the manufacturer's specification, such as a different profile, a wider size, or a run-flat variant on a vehicle not originally equipped for them.
Tyres and the MOT Test
Tyres are consistently one of the most common reasons for an MOT failure. Knowing what the tester checks helps you identify problems in advance, potentially saving the cost and inconvenience of a re-test.
What the MOT tester examines
The DVSA's MOT inspection manual covers tyres in section 5. For each tyre, the examiner checks:
- Tread depth across the central three-quarters of the breadth and around the full circumference, using a gauge
- Tyre condition: cuts, bulges, exposed cord or ply, excessive sidewall cracking
- Correct seating on the rim, with no damage to the bead area
- Compatibility of tyre types: radial and cross-ply must not be mixed on the same axle
- Size: the tyre must conform to the manufacturer's specification or an approved alternative
- Visible inflation: obviously flat or severely deflated tyres will fail
Failure versus advisory
A tyre at or below 1.6mm tread depth is an automatic MOT failure. So is any bulge, any cut that exposes the structural cord, and any other serious defect. An advisory is issued where the tyre is legal but the tester considers the remaining life limited. A tread depth between 1.6mm and about 2mm, or minor surface cracking that is present but not yet dangerous, typically generates an advisory rather than a failure. Advisories do not prevent the car from passing its MOT, but they should be acted on. An advisory that is ignored and later contributes to an accident can feature in an insurance investigation.
Cost implications
If your car fails on a tyre, you will need to have the tyre replaced before the test can be passed. If you return to the same test station on the same or the next working day, the recheck of the failed item is usually included at no extra charge or for a reduced re-test fee. Budget tyres for a standard fitment such as 205/55 R16 start from around £50 to £60 fitted. Premium brands in the same size typically cost £100 to £160 or more. Prices change, so always verify current figures with a tyre supplier before your test date.
When Should You Actually Replace a Tyre
The law requires replacement at 1.6mm. The evidence consistently points to a different, earlier threshold. The gap between the two matters for both safety and insurance purposes.
The case for 3mm
TyreSafe, the UK's tyre safety charity, recommends replacing car tyres when the tread depth reaches 3mm rather than waiting for the legal minimum of 1.6mm. The reasoning is grounded in stopping distance data. In wet conditions, tyre tread channels water away from the contact patch to maintain grip. As tread depth falls, this clearing capacity reduces. TyreSafe testing has demonstrated that stopping distances in wet conditions can be around 44% longer on a tyre at 1.6mm compared to one at 3mm. At 70mph on a motorway in rain, that extra distance is the difference between a near-miss and a collision. Replacing at 3mm rather than 1.6mm means buying more tyres over time, but the reduction in wet-weather accident risk is the calculation most tyre safety organisations and major manufacturers ask drivers to make.
Tyre age: the hidden risk
Even a tyre with substantial remaining tread can become unsafe as it ages. Ultraviolet light, ozone, heat cycling and the simple passage of time cause the rubber compound to harden and become more brittle. Internal micro-cracking can develop that is not visible from the outside but that can precede a sudden structural failure. TyreSafe and the British Tyre Manufacturers' Association both recommend having tyres professionally inspected once they reach five years old and replacing them at ten years regardless of tread depth or outward appearance. The DOT date code is the definitive reference. If you are looking at a used car with tyres that have good tread but a manufacturing date eight or nine years ago, the tyres are not a selling point.
Tyre Types and What the Law Says About Them
The UK has no legal requirement to fit seasonal tyres at any time of year, which distinguishes it from several European countries. However, the choice of tyre type has real implications for safety and for how an accident might be assessed by an insurer.
Summer tyres
Standard passenger car tyres sold in the UK are summer tyres. Their rubber compound is designed to perform at temperatures above approximately 7 degrees Celsius. Below that temperature, the compound begins to harden, reducing grip on cold wet roads even in the absence of frost or ice. In northern England, Scotland and Wales, temperatures below 7 degrees are common for several months of the year. This does not make summer tyres illegal in those conditions, but it is relevant to the level of grip available.
Winter tyres
Winter tyres use a softer rubber compound that remains pliable at low temperatures and a tread pattern with additional sipes, which are thin cuts in the tread blocks that create extra biting edges on slippery surfaces. The marking to look for is the Three-Peak Mountain Snowflake symbol (3PMSF), which indicates the tyre has passed a formal wet-snow traction test. The M+S marking (mud and snow) is a less stringent designation and is found on a wide range of tyres. Winter tyres are not only for snow: they outperform summer tyres on cold dry roads and in cold rain. The 1.6mm legal minimum tread depth applies to winter tyres in exactly the same way as to any other tyre.
All-season tyres
All-season or all-weather tyres offer a compromise between summer and winter performance. They use a compound and tread design intended to perform adequately across the full range of temperatures and conditions a UK driver might face, from warm dry motorways to cold wet B-roads in January. They will not match a dedicated summer tyre in peak summer conditions or a dedicated winter tyre in heavy snow, but the performance gap has narrowed in recent years. Many carry both M+S and 3PMSF markings. All-season tyres are an increasingly practical choice for UK drivers who do not want to manage two sets of wheels and seasonal changes.
Tyre choice and your insurance
Fitting standard winter or all-season tyres to your existing wheels is generally not a modification that requires notification to your insurer. If you fit a second set of wheels with winter tyres, check your policy or contact your insurer to confirm cover is unaffected. The more significant insurance point is this: fitting appropriate tyres for the season and conditions is evidence of responsible vehicle maintenance. Being in a winter accident on a car that has been driven through months of sub-7-degree weather on summer tyres is a factual detail that an insurer or a court may take into account when assessing fault and the state of the vehicle.
Run-Flat Tyres: What Drivers Need to Know
Run-flat tyres have reinforced sidewalls designed to support the vehicle's weight after a puncture, allowing limited continued driving, typically up to 80km at a maximum of 80km/h. The specific limits are marked on the tyre and must be observed. They are fitted as standard on many newer vehicles, often with no spare wheel provided.
A run-flat tyre that has been driven on in a deflated or low-pressure state must be replaced, not repaired. The sidewall reinforcement takes on the full load of the vehicle, and this typically causes internal damage that is not detectable from outside. Fitting a repaired run-flat is a safety risk. From a legal and MOT standpoint, run-flat tyres must meet the same 1.6mm tread depth and condition requirements as any other tyre. Because they cost more than standard equivalents, factoring their replacement into your car's running costs is worth doing when you buy a vehicle equipped with them. Our running costs guide covers depreciation and ongoing ownership expenses in more detail.
Frequently Asked Questions
What is the legal minimum tyre tread depth in the UK?
The legal minimum is 1.6mm of tread depth across the central three-quarters of the tyre's width and continuously around the entire circumference. This applies to cars and light vans under the Road Vehicles (Construction and Use) Regulations 1986. Most tyre safety organisations, including TyreSafe and the British Tyre Manufacturers' Association, recommend replacing tyres at 3mm because wet-weather stopping distances increase substantially as tread approaches the legal limit.
Can I drive on a tyre with a bulge in the sidewall?
No. A sidewall bulge indicates damage to the internal structural layer of the tyre and it can fail without any further warning. Driving on a bulging tyre is an offence under the Construction and Use Regulations regardless of tread depth, and it is an automatic MOT failure. Do not drive the car until the tyre is replaced. If you are not confident the vehicle can be moved safely to a tyre centre, contact your breakdown provider.
Will my car insurance pay out if I have an accident with illegal tyres?
Not necessarily. Most UK car insurance policies contain a condition requiring the vehicle to be in a roadworthy, legal state, and tyres below the 1.6mm minimum breach that condition. Your insurer may reduce or refuse your own-damage payout. Insurers are legally required to meet valid third-party claims under the Road Traffic Act 1988, but they can then exercise their right of subrogation to recover those costs from you. In practice, illegal tyres can leave you personally liable for both sides of a significant accident.
How do I find out how old my tyres are?
Look for the DOT code on the tyre sidewall. After the letters "DOT" there is a series of characters. The last four digits give the manufacturing date: the first two digits are the week of manufacture and the second two are the year. A code ending in "2421" means the tyre was made in the 24th week of 2021. There is no UK law setting a maximum tyre age, but professional inspection is recommended after five years and replacement is generally advised at ten years regardless of remaining tread depth or visual condition.
Do I need to tell my insurer if I fit winter tyres?
Fitting standard winter tyres to your existing wheels is generally not a notifiable modification, but the safest approach is to check your specific policy wording. If you fit a separate set of alloys with winter tyres, inform your insurer to confirm cover is not affected. When fitting non-standard tyre sizes or run-flat variants on a vehicle not designed for them, notification is more important. A brief call or email to your insurer creates a record that the change was disclosed.
How many penalty points do I get for illegal tyres?
Each illegal tyre carries a maximum of three penalty points. Four illegal tyres therefore risk twelve points and automatic disqualification for most full licence holders under the totting-up procedure. Drivers who qualified less than two years ago face revocation of their licence at just six points. Each illegal tyre also carries a maximum court fine of £2,500, though police also have the option of issuing a Vehicle Defect Rectification Scheme notice or a Fixed Penalty Notice in less serious cases. Always verify current sentencing guidelines at the government's official sentencing website.
If you want independent guidance on what your car insurance policy actually covers, or you have a specific question about how a vehicle condition might affect a claim, contact us through our contact page. We do not sell insurance products, but we can help you understand your policy and work out the right questions to ask your insurer.