Tyres are essential to your driving experience, but let’s face it — they can be baffling. The sizes, the labels, the tech: it’s a lot to take in. Whether you’re picking a set of winter tyres or comparing your options on a budget, understanding the basics is key. Tyre sizing alone feels like cracking a code, with those sidewall numbers often seeming designed to confuse.
But don’t worry — we’ve got you covered. We’ll guide you through everything from width and profile to speed ratings, helping you make confident choices for any season or situation.
Why do I need to know about tyre sizes?
If you bought your car new and plan to get tyres replaced at a dealer or tyre shop, you usually don’t need to worry about the exact tyre specifications — they’ll handle it for you. Plus, your car’s tyre size and recommended pressure are usually listed on a label inside the driver’s door or fuel flap for emergencies like blowouts.
But if you’re buying tyres online, purchasing a used car, or considering winter or performance upgrades, knowing your tyre size is essential. It ensures you get the right fit, stay safe and legal, and find the best deals.
Where can I find my tyre size?
Your tyre size is typically shown on the sidewall and follows a standard format of numbers and letters, used universally by manufacturers to indicate key dimensions.
For a quick check, look inside the driver’s door frame or the fuel filler flap for a sticker with tyre details and pressures. It’s also listed in the car’s handbook. If you’re unsure, many online tyre retailers let you enter your registration number to find the correct size.
How to read tyre sizes
Now that you’ve spotted the series of letters and numbers on your tyre’s sidewall, it’s time to break it down. Don’t worry — it’s simpler than it looks!
While tyre sizes can vary between cars, they usually follow a standard pattern like this: 195/55 R16 87V. This is a typical example we’ll use to explain what each number and letter represents, helping you understand your own tyre size with ease.
The numbers always break down in the following way:
Tyre width (195)
This number indicates the tyre’s width in millimetres. Generally, a wider tyre offers more grip, but it’s not always that simple — other factors such as tread design and road conditions also play a role.
Tyre height (55)
This number represents the tyre’s sidewall height as a percentage of the tyre’s width. In this case, a 55 profile means the sidewall height is 55% of the width (so, 107.25mm for a 195mm wide tyre). A lower number typically gives a shorter, sportier sidewall — which is why you often see high performance cars described as being fitted with ‘low profile tyres’. A higher number usually indicates more comfort.
Tyre radius (R)
The “R” stands for radial, indicating the type of construction used in the tyre. Radial tyres have layers of steel or fabric that run radially from the centre, which provides better durability and performance. Before radial tyres became standard, tyres used a “crossply” design, but today, almost all road cars use radial tyres for improved stability and handling.
Rim diameter (16)
The “16” refers to the size of the wheel rim in inches. This means the tyre is designed to fit a 16-inch rim. When choosing replacement tyres, it’s important to match this number with your car’s wheel size, as fitting the wrong size can affect performance and safety.
Load index (87)
The number ’87’ represents the tyre’s load rating. The higher the number, the more weight each tyre is able to safely carry. In this instance, 87 would equal 615kg. Multiply that figure by four, and you get an idea of the total load your car can carry.
Tyre speed rating (V)
Ending the sequence is the letter ‘V’ which relates to the speed rating. The higher the letter, the faster speed your car is capable of travelling safely. In this case, the tyre is guaranteed up to 149mph. There is a table of speed ratings below.
Tyre speed rating guide
- N 87mph
- P 93mph
- Q 99mph
- R 106mph
- S 112mph
- T 118mph
- U 124mph
- H 130mph
- V 149mph
- Z 150mph+
- W 168mph
- Y 186mph
Why it’s important to get the right tyres
It might be tempting to save money by opting for tyres with a lower speed rating, especially in speed-limited UK where 150mph+ capabilities seem excessive. But these ratings exist for a reason.
Some manufacturers, like Mercedes-Benz, even offer tyres specially matched to their cars, complete with OEM approval. And if your car has run flat tyres, you’ll need the correct ones to match the rims.
The right tyres aren’t just about performance; they ensure proper wear, heat resistance, and most importantly, safety. Plus, fitting the wrong tyres could invalidate your insurance. Unsure? Always double-check with an expert.
FAQs
What’s the difference between summer, winter, and all-season tyres?
Summer, winter, and all-season tyres are each designed for specific conditions. Summer tyres are your go-to for warmer months, delivering better grip and handling on dry roads. Winter tyres are made for colder weather, with a special tread and softer rubber to tackle ice, snow, and slippery surfaces. All-season tyres are a do-it-all option, giving decent performance year-round in milder climates without the hassle of swapping tyres every season.
Why do tyre sizes vary between front and rear wheels?
On some cars — particularly sporty or performance models — the front and rear tyres are different sizes. This staggered setup isn’t just for show; it’s all about improving grip and handling, especially at higher speeds or during hard cornering. It’s a deliberate design choice to optimise performance.
Do I need to tell my insurer if I change tyre sizes?
Yes, absolutely. If the new tyre size doesn’t match your car manufacturer’s recommendations, you’ll need to let your insurer know. Failing to do so could invalidate your policy, so it’s always better to play it safe.
Looking for more jargon-busting motoring meanings? Head over to our Parkers Car Glossary page and take a look at our other definitions.
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