How to Read the Numbers on Your Tyre Sidewall (and Buy the Right Replacement)

• The main code on a tyre, such as 205/55 R16 91V, gives the width in millimetres, the sidewall height as a percentage of that width, the construction, the wheel size in inches, the load index and the speed rating.
• The last four digits of the DOT code tell you the week and year the tyre was made, so 0524 means week five of 2024.
• Replacements should match the size in your handbook and meet or beat its load and speed ratings; a set of four mid-range 205/55 R16 tyres typically costs £320 to £550 fitted (about $430 to $740).

Your Tyre Sidewall Tells You the Size, Load, Speed Rating and Age You Need

Every number on your tyre sidewall has a job, and once you know the order they come in, reading them takes about ten seconds. Take the common UK size 205/55 R16 91V. The 205 is the tyre width in millimetres. The 55 is the aspect ratio, meaning the sidewall height is 55 percent of the width. R means radial construction, which covers almost every modern car tyre. The 16 is the diameter of the wheel rim in inches. The 91 is the load index, and the V is the speed rating.

That single line is all you need to buy a like for like replacement. Pirelli and TyreSafe both explain the sequence the same way, and it applies to every mainstream tyre brand sold in the UK. The rest of the sidewall holds the tyre’s age, its approval marks and any special features, which are worth checking before you hand over money for new rubber.

Load Index and Speed Rating: The Two Numbers People Get Wrong

The load index is the two or three digit number after the rim size. It is a code, not a figure in kilograms. You look it up on a load index chart to find the maximum load each tyre can carry when correctly inflated. A load index of 91, for example, means 615kg per tyre.

The speed rating is the letter after the load index. It shows the maximum speed the tyre is built to sustain when correctly inflated and carrying its rated load. The ratings you will see most on UK cars are:

• T: up to 118mph (190km/h)
• H: up to 130mph (210km/h)
• V: up to 149mph (240km/h)
• W: up to 168mph (270km/h)
• Y: up to 186mph (300km/h)

Nobody should be driving at those speeds on a public road, so it is tempting to think the letter is irrelevant. It is not. The speed rating also reflects how the tyre copes with heat build up, cornering loads and braking, and your car’s manufacturer has specified a minimum rating for a reason.

The rule is simple: replacement tyres should match or exceed the load index and speed rating listed in your handbook or on the tyre placard in the door shut. Going higher is fine. Going lower is where drivers get into trouble. Fitting an under rated tyre is not illegal in itself, but TyreSafe warns it can compromise safety and void the manufacturer’s guarantee, and tyre retailers including Point S and ASDA Tyres point out that insurers can refuse a claim if the tyres fitted do not meet the manufacturer’s specification. If a fitter offers a cheaper tyre with a lower letter or number than your current set, ask why before you agree.

You will sometimes see XL or Extra Load next to the load index. This means the tyre is reinforced to carry more than a standard tyre of the same size. Many larger cars, SUVs and electric cars, which are heavier than their petrol equivalents, list XL tyres as standard. If your current tyres are XL, replace them with XL.

How to Check How Old Your Tyres Are

Look for the letters DOT on the sidewall, followed by a string of seven to 13 letters and numbers. Pirelli explains that the first block identifies the factory, the next identifies the size, and the final four digits, usually inside a small raised oval, are the date code. The first two digits are the week of manufacture and the last two are the year. A tyre stamped 1223 was made in the 12th week of 2023. A three digit code means the tyre was made before 2000.

If you can see the DOT letters but no date, check the other side. Pirelli notes manufacturers only have to stamp the full code on one sidewall, not both.

There is no legal age limit for tyres on private cars in the UK. The MOT tyre age check, which fails tyres more than ten years old, applies to buses, coaches and minibuses with more than eight passenger seats. For ordinary cars, age is a judgement call. Rubber hardens over time, and Pirelli points out that tyres with plenty of tread left still age regardless of mileage. Tyres on a car that sits unused for long spells, a caravan or a spare wheel that has never touched the road are the ones most likely to be old enough to worry about. Look for fine cracking in the sidewall or between the tread blocks, and ask a tyre fitter to inspect any tyre that looks tired when the tread still passes.

For checking the tread itself, our guide on how to check tyre tread properly covers the legal 1.6mm limit and the quick 20p test.

The Other Sidewall Markings and What the MOT Checks

Beyond the size, load and speed codes, you will find a handful of other markings:

• Maximum pressure: a figure in PSI and kPa, usually in small print near the rim. This is the most the tyre can safely hold, not the pressure you should run. Use the figure in your handbook, on the door shut placard or inside the fuel flap.
• E mark: a capital E in a circle followed by a number, showing the tyre is approved to European standards. The MOT inspection manual says tyres marked “Not for Highway Use” are only acceptable if they also carry this E mark and approval number.
• Rotation arrow or “Outside” marking: directional tyres have an arrow showing which way they should turn, and asymmetric tyres are marked to show which face goes on the outside.
• M+S: mud and snow. This is a tread design claim by the manufacturer, not proof of tested winter grip.
• 3PMSF: a three peak mountain with a snowflake inside. This shows the tyre has passed a standardised snow performance test, and is the marking to look for on winter or all season tyres.
• Run flat markings: run flat tyres carry a code such as RFT or the manufacturer’s own abbreviation. Replace run flats with run flats unless your car has been set up with a spare wheel or repair kit.

The DVSA MOT inspection manual for cars treats several sidewall related faults as a major defect, which is an automatic fail. These include different sized tyres on the same axle, tyres of different construction on the same axle (such as radial and cross ply), and a tyre not fitted in line with the manufacturer’s sidewall instructions. An asymmetric tyre fitted the wrong way round is not a reason for failure on its own, but the tester will advise you about it. Tread below 1.6mm across the central three quarters of the tyre is recorded as a dangerous defect.

The formal MOT check of load and speed ratings against axle loads applies to Class 5 and Class 7 vehicles, such as larger minibuses and goods vehicles. For a normal car, the handbook specification is still what your insurer and your safety depend on.

How to Use the Sidewall to Buy the Right Replacement

When one or more tyres need replacing, run through this before you order:

• Read the full size code from the tyre you are replacing and check it against your handbook, not just against the other tyres. A previous owner or garage can have fitted the wrong size.
• Match or exceed the load index and speed rating. Keep XL if the original was XL.
• Keep both tyres on the same axle identical in size and construction. Most fitters recommend replacing in pairs per axle so the grip and wear stay even from side to side.
• If you drive on rural roads in winter, look for the 3PMSF mark rather than M+S alone.
• Ask to see the DOT date on new tyres before they are fitted. Stock that has sat in a warehouse for a long time is less desirable than recent production.

On price, TyreCost’s 2026 guide puts a set of four 205/55 R16 tyres, the most popular UK size, at roughly £230 (about $310) for budget brands, £320 to £550 (about $430 to $740) for mid-range brands, and £500 to £800 (about $670 to $1,070) for premium brands, fitted with balancing and disposal. A two wheel alignment adds around £40 (about $55). Larger rims, lower aspect ratios, XL construction and run flat technology all push the price up, so the sidewall code is also the quickest way to understand why one quote is higher than another.

Once you know how to read it, the sidewall does the work for you. Photograph the code on your phone, keep it with your car documents, and you will never have to guess the size at a tyre fitter’s counter again.

Sources

• GOV.UK: MOT inspection manual, axles, wheels, tyres and suspension
• Pirelli: Tyre DOT code, what it is and how to read it
• Pirelli: Tyre markings explained
• TyreSafe: Tyre speed ratings explained
• Point S: Speed rating on tyres and insurance rules
• Michelin UK: Winter tyre markings
• TyreCost: Tyre cost UK 2026