Tyres and the Law: Tread, Markings, Age and What Testers Check

Written by the MOT Check Now editorial team and checked against GOV.UK and DVSA guidance. Last updated 3 November 2026. Read our editorial policy and how we get our data.

Tyres are the only part of your car that touches the road, and they are checked at every MOT. They are also one of the easiest things to inspect yourself. This guide on MOT Check Now sets out the legal tread depth, what MOT testers look for, how to read the numbers on the sidewall, what we can and cannot say about tyre age, and the penalties for driving on unsafe tyres. We are an independent site, not affiliated with DVLA or DVSA, and where a rule matters we name the official source so you can check it yourself.

Key facts at a glance

The legal minimum tread depth

For cars, light vans and light trailers the legal minimum is 1.6mm. The tread must meet that depth across the central three-quarters of the tyre and around its whole circumference. Motorcycles, large vehicles and passenger-carrying vehicles need at least 1mm, and mopeds need visible tread.

The outer edges of the tread, beyond that central three-quarters, are not covered by the 1.6mm rule for a car, but that does not make a tyre safe. Uneven wear usually signals a cause worth fixing, such as incorrect pressure, tracking problems or worn suspension. DVSA guidance says the measurement is taken in the primary grooves, the ones that contain the tread wear indicators, and that shallower secondary grooves do not decide the result.

A tread depth gauge is the accurate way to check. The 20p coin test is a rough warning at best: official advice says that if you can see the outer rim of the coin when it sits in the main grooves, have the tyre checked by a professional. Do not treat a coin as proof that you are legal.

How to measure tread properly

1. Park on level ground and make sure the tyres are clean. Stones and mud in the grooves can give a false reading.
2. Use a tread depth gauge. Gauges are inexpensive and give a number in millimetres.
3. Measure in the main grooves. These are the primary grooves that contain the tread wear indicators.
4. Measure at several points across the central three-quarters. Take readings near the inner, middle and outer parts of that band.
5. Repeat at several places around the tyre. The requirement applies around the full circumference, so rotate the wheel and measure again.
6. Record the lowest reading. That is the figure that matters.
7. Repeat for all four tyres, and check the spare if you rely on it. The MOT does not inspect the spare, but a worn spare is no help in a breakdown.

Illustrative example. You measure a front tyre at three points across the central band and get readings that fall as you move round the tyre. The lowest reading is the one that counts. If the lowest is below 1.6mm, the tyre is below the legal minimum for a car and should be replaced before you drive. A tyre that is only just above the limit is legal but has little left, and wet grip will already be reduced.

Tread wear indicators

Most tyres have small raised bars in the base of the main grooves, called tread wear indicators, and a marker on the sidewall shows where they are. When the tread wears down level with these bars, the tyre is at or near the legal minimum. They are a handy visual cue, but they are not a substitute for measuring, because a gauge tells you how much margin remains before you reach them. Do not wait until the bars are flush before you act: a tyre that has just reached the minimum has little spare grip in the wet.

The 20p test, used carefully

The coin test is a quick check you can do in a car park. Place a 20p coin into the main grooves. If you can see the outer rim of the coin, official advice is to have the tyre checked by a professional. If you cannot, the tyre may be fine, but the coin does not prove it is legal, and it cannot show whether the depth is the same all the way round. Treat it as a prompt to measure, not an answer. A tread depth gauge costs little compared with the price of a tyre or a fine.

What the MOT checks on tyres

The tester looks at tyre condition, security, size and type, and tread depth. The spare wheel is not inspected. Under the inspection manual the main tyre defects are:

• Tread below the requirement. This is a dangerous defect, which means an immediate fail and a car that should not be driven.
• Cuts deep enough to reach the ply or cords. A major defect.
• A lump, bulge or tear caused by separation or partial failure of the structure. A dangerous defect.
• Load capacity or speed rating below the minimum requirement. A major defect.
• Different sizes on the same axle, or different structures on the same axle, such as radial and cross-ply together. A major defect.
• A tyre not fitted according to the manufacturer’s sidewall instructions, for example directional or inside and outside markings. A major defect.
• A tyre pressure monitoring system that is faulty, on cars first used on or after 1 January 2012. A major defect.
• A tyre that is obviously under-inflated. A minor defect, which passes but is recorded.

Wear that is close to the limit often appears as an advisory. Our guide to MOT advisories explained shows why that matters, and MOT failure reasons lists the other areas of the car.

The defect categories in plain English

Since 20 May 2018, MOT defects fall into four categories. Dangerous means the fault is a direct and immediate risk to road safety. The vehicle fails, must never be driven, and it is illegal to drive on the road whether or not an MOT is current. Major means the vehicle fails and the defect needs fixing. Minor means the fault is present but not serious enough to fail the test, so the vehicle passes. An advisory means a component is not yet defective but may become so soon. Our MOT defect categories guide has the full explanation, and what to do after a failed MOT covers repairs and retests.

Tyre pressure monitoring systems

Many cars first used on or after 1 January 2012 have a tyre pressure monitoring system. At the MOT, a faulty system is a major defect. The warning lamp on the dashboard is one of the warning lamps the test covers, together with airbags, ABS, electronic stability control and electronic power steering. If your tyre pressure lamp is on, check the pressures with a gauge when the tyres are cold. If the lamp stays on after the pressures are correct, there may be a sensor fault or a system that needs resetting, so ask a garage. Do not rely on the lamp alone, because the system warns you about a significant pressure loss and not about slow, small changes. Weekly checks with a gauge are still the best habit.

Mixing tyres

Tyres on the same axle need to be the same size and the same structure. Fitting two different sizes on one axle, or a mix of radial and cross-ply, is a major defect. This is also a practical issue: unmatched tyres can behave differently under braking and cornering. When you replace tyres, do not assume that matching the old ones is enough. Check the sizes and specification against your handbook, and when you replace only one tyre, ask the fitter about the brand and tread of the other tyres on that axle. We do not publish rules on partial replacement beyond what the inspection manual states.

How to read the sidewall markings

The sidewall carries a string of letters and numbers. A typical example reads 205/55 R16 91V, and it breaks down as follows.

1. 205 is the section width in millimetres.
2. 55 is the aspect ratio, the height of the sidewall as a percentage of the width.
3. R shows radial construction, and 16 is the rim diameter in inches.
4. 91 is the load index, a code for the weight the tyre can carry. Look it up in the manufacturer’s table and never go below what your handbook specifies.
5. V is the speed rating, a code for the maximum speed the tyre is designed for.

Other marks include the tread wear indicator symbol, XL or reinforced for extra load, M+S or a snowflake for winter capability, and arrows that show rotation direction. Your car’s recommended sizes and pressures are in the handbook and often on a sticker inside the door or fuel flap. Pressures should be checked weekly, before a journey and while the tyres are cold, using the manufacturer’s figure for your load, because under or over-inflation harms braking and steering.

Why load index and speed rating matter

A tyre with a load capacity or speed rating below the minimum requirement for the vehicle is a major MOT defect. These ratings exist because tyres are designed for a particular range of loads and speeds, and a tyre used outside that range can overheat or fail. When you buy replacements, match or exceed the figures in the handbook, and ask the fitter to confirm. We do not reproduce load or speed tables, because they are long, vary by manufacturer and should come from your handbook or the tyre maker.

Pressure: the weekly habit

Correct pressure is the cheapest way to protect tyres. Check pressures weekly, before a journey, and when the tyres are cold, because pressure rises as the tyres warm up. Use the figures in the handbook or on the sticker inside the door or fuel flap, and use the setting for your load if the handbook gives one. Under-inflation overheats the tyre and wears the outer edges, while over-inflation reduces the contact patch and wears the centre. Both harm braking and steering. An obviously under-inflated tyre is a minor defect at the MOT, which passes but is recorded, so a pass does not mean the pressure is right. Re-check the spare as well if you carry one.

Tyre age and the date code

Rubber hardens and cracks with time even when tread looks fine. Look for the DOT code on the sidewall: the last four digits normally give the week and year of manufacture, so 2423 would mean week 24 of 2023. Some codes are only on the inner sidewall, so you may need to check the other side or the back of the wheel.

We have not found an official fixed age limit for ordinary car tyres, so we do not quote one. The legal rule that does exist applies to heavier vehicles: tyres over 10 years old must not be used on the front axles of goods vehicles over 3.5 tonnes and passenger vehicles with more than 8 seats. For cars the safe approach is to follow the tyre maker’s and your vehicle manufacturer’s advice, inspect tyres for cracking, and replace any that look perished or have been stored or used in poor conditions.

Reading a date code

Illustrative example. A sidewall shows the letters DOT followed by a series of characters, ending in the digits 3119. The last four digits are 3119, so the tyre was made in week 31 of 2019. If the tyre is on a car you are viewing, work out its age from that date and compare it with the car’s age. Tyres that are much older than the rest of the car, or that show cracking in the sidewall or between the tread blocks, deserve a closer look. If you cannot find a code on the outer sidewall, look at the inner side, which sometimes needs the wheel to be turned or the car to be lifted.

Tyres on cars that are used rarely

Cars that stand for long periods can develop flat spots and perished rubber even with plenty of tread. If you own a classic, a second car or a vehicle that has been declared off the road, check the tyres before you use it. The SORN check shows whether a vehicle is recorded as off the road, and the car tax check shows tax status. Exempt historic vehicles still have to be roadworthy, and tyres are part of that. See MOT exempt vehicles for the rules on which vehicles do not need a test.

Damage, repairs and uneven wear

What damage looks like

Look for cuts, bulges, lumps, cracks, objects embedded in the tread and signs of rubbing. A cut deep enough to reach the ply or cords is a major defect. A lump, bulge or tear caused by separation or partial failure of the structure is a dangerous defect, so a car with such a tyre must not be driven. Bulges often come from impact damage, such as hitting a kerb or a pothole, and the damage may be on the inside of the tyre where you cannot see it. If you have had a hard impact, have the tyre inspected even if it looks normal from the outside.

What uneven wear tells you

Uneven wear is a clue to a different problem. As a general guide: wear on both outer edges often means the tyre has been run under-inflated; wear down the middle often means it has been over-inflated; wear on only one edge can point to a tracking or alignment problem; and patchy or scalloped wear can suggest worn suspension components. These are general patterns, not a diagnosis, so use them as prompts to ask a garage. Fixing the cause matters as much as replacing the tyre, otherwise the new tyre wears the same way.

Repairs and replacements

Punctures and damage are best assessed by a tyre professional, who can tell you whether a repair is suitable and safe. We do not publish repair rules, because they depend on where the damage is and on the tyre type. Fit replacements that match your handbook. When buying a replacement, ask about the tyre’s date code, so you know how old it is. If you are considering part-worn tyres, ask for the age, condition and any repair history in writing, and check them yourself. Reliable fitters will explain the options without pressure.

Summer, winter and all-season tyres

Many tyres carry markings such as M+S or a snowflake to show winter capability. We have not found a legal requirement for winter tyres on UK roads, so choosing between summer, winter and all-season tyres is a safety and cost decision. The key legal rule is the same for all of them: the tread must meet the minimum depth, the tyres must match on each axle and the load and speed ratings must meet your vehicle’s requirements. Winter and all-season tyres can offer better grip in cold, wet conditions, but they wear and age like other tyres, so the checks in this guide apply equally.

Electric vehicles and tyres

Electric vehicles are often heavy and deliver torque instantly, so tyres can wear faster and the correct load rating matters. Some are fitted with tyres designed for electric vehicles, and the handbook will specify the required type. The MOT still checks tread, condition, size, type, security and the tyre pressure monitoring system. If you are buying a used electric car, look at the tyre advisories in the MOT history and consider the cost of replacements as part of the purchase decision. Our car battery guide covers the 12V battery on electric cars, which is a separate matter.

Penalties for unsafe tyres

There is no separate headline penalty for bald tyres in the sources we checked. Defective tyres usually fall under the offence of using a vehicle in a dangerous condition, which can bring a fine of up to £2,500, a driving ban and 3 penalty points. Driving after a failed MOT with a dangerous defect carries the same exposure. Driving without a valid MOT can cost up to £1,000. Set against those figures, replacing a worn tyre is the cheaper option.

Beyond the penalties, unsafe tyres affect your safety and other road users. Braking distances increase on worn tyres, especially in the wet, and a damaged tyre can fail without warning. Check your insurance policy terms as well, because insurers can take the condition of a vehicle into account in some circumstances. We do not give insurance advice and cannot say how a particular policy treats tyre condition, so read your policy or ask your insurer. See our driving without an MOT guide for the MOT penalties in full.

Practical monthly tyre check

1. Check pressures when the tyres are cold and set them to the handbook figures.
2. Measure tread at several points across the central three-quarters and around the tyre.
3. Look for cuts, bulges, cracking, embedded objects and uneven wear.
4. Check the valve caps and the condition of the wheels.
5. Make sure all four tyres, and ideally each axle pair, match in size and type.
6. Replace tyres early rather than waiting for the limit, since wet grip falls as tread wears.

When buying a car, past tyre advisories in the MOT history are a useful sign of how the car was looked after, and the used car checklist includes tyres. Check your own test date on the MOT check.

Worked examples

These are illustrative examples, invented to show how the rules apply.

Example 1: a tyre close to the limit

A driver measures the front tyres and finds the lowest reading is only slightly above 1.6mm. The tyres are legal, so the car would pass on tread, but the tester may note wear near the limit as an advisory. The driver replaces the tyres before the test rather than waiting for the next frost and wet roads.

Example 2: a bulge after a pothole

After hitting a pothole, a driver notices a small bulge on a sidewall. A lump or bulge caused by separation of the structure is a dangerous defect, so the car would fail the MOT and should not be driven. The driver has the tyre replaced immediately and does not wait for the test.

Example 3: mixed tyres on an axle

An owner replaces one front tyre with a different size because it was cheaper. At the test, different sizes on the same axle are a major defect, so the car fails. The owner has to fit a matching tyre and arrange a retest. Matching the specification at the time of purchase would have avoided both the cost and the time.

Example 4: an old but unworn tyre

A car shows plenty of tread, but the DOT code reads week 12 of an old year, and the sidewall shows fine cracks. We do not quote a fixed age limit for car tyres, so there is no legal cut-off to apply, but cracking is a sign that the rubber is perished. The sensible move is to ask a tyre professional to inspect it and, if in doubt, replace it.

Common mistakes

• Relying on the 20p test as proof. It is a rough warning only.
• Measuring in only one place. The requirement covers the central three-quarters and the whole circumference.
• Ignoring uneven wear. It usually points to pressure, alignment or suspension problems.
• Checking pressure on warm tyres. Cold readings are the ones to compare with the handbook.
• Forgetting the age of the tyre. Rubber ages even when tread looks fine.
• Mixing sizes or structures on an axle. This is a major MOT defect.
• Ignoring the tyre pressure warning lamp. A faulty system is a major defect on cars first used from 1 January 2012.
• Assuming the spare is checked. It is not inspected at the MOT.
• Leaving it until the test. A dangerous defect means a fail and a car that cannot legally be driven.

What our free tools can and cannot tell you about tyres

Our tools read the DVSA MOT history and DVLA vehicle data. The history can show whether past tests recorded tyre advisories, minor defects or failures, which is a useful guide to how a car has been maintained. You can follow recurring items with the advisory tracker, and our guide to reading MOT history explains the terms. The data does not record current tread depth, tyre brand, tyre age or pressure, so it cannot tell you the state of the tyres today. A full vehicle report puts the MOT timeline and recurring advisories into a PDF, but it does not include finance, stolen or write-off data. For the other basics, the vehicle check, mileage check, MOT reminder and our guides library cover the rest, and how we get our data explains the sources.

Before your MOT

A tyre check takes a few minutes, and fixing problems first avoids a fail. Measure the tread, check the pressures, look for damage and make sure the tyre pressure lamp is not lit. Our preparing for an MOT guide and MOT test checklist go through the rest of the car. If a tyre needs replacing, do it before the test, because a fail on a dangerous tread defect means you cannot drive the car away unless it is repaired. If you need a centre, see finding an MOT test centre, and if you need to move your booking, read cancel or rebook an MOT.

Glossary

Tread depth

The depth of the grooves in the tyre, measured in millimetres.

Central three-quarters

The middle part of the tread width over which the 1.6mm minimum applies for cars.

Tread wear indicator

A small raised bar in the base of the main grooves that shows when the tread is at or near the minimum.

Aspect ratio

The height of the sidewall as a percentage of the tyre width.

Load index

A code for the weight a tyre can carry.

Speed rating

A letter code for the maximum speed a tyre is designed for.

DOT code

The marking on the sidewall whose last four digits normally give the week and year of manufacture.

Ply or cords

The internal structure of the tyre. A cut that reaches them is a major defect.

TPMS

Tyre pressure monitoring system, which warns of low pressure on many cars first used on or after 1 January 2012.

Radial and cross-ply

Two tyre constructions. Mixing them on one axle is a major defect.

Sources and further reading

• GOV.UK, the pages on tyres and vehicle condition, for the legal minimum tread depth and the 20p coin advice.
• DVSA, MOT inspection manual for private passenger and light commercial vehicles, as published on GOV.UK, for the tyre defects and categories.
• GOV.UK, “Getting an MOT” and the MOT test fee page, for MOT timing and penalties.
• Your vehicle handbook and the tyre manufacturer, for sizes, load index, speed rating and pressures.
• Contains public sector information licensed under the Open Government Licence v3.0.