Knowing how to read your tyre size saves time on the phone and helps us advise you properly. It’s printed on the sidewall as a string like 205/55 R16 91V. We cover drivers across Essex and London, and the size is one of the first things we’ll ask for. This guide walks you through finding it, decoding it, and passing it on before you call or fill in the free quote form.
Where to find the size on the tyre
The size is moulded into the outer sidewall, the side of the tyre you see when you stand beside the car. Look for a group of numbers with a slash and the letter R in the middle. Start there.
It’s usually raised rubber in the same colour as the tyre, so it can be hard to spot. A light held at an angle across the sidewall often makes the characters stand out.
If the outer side is scuffed or caked in mud, check the inside face of the same tyre, or read the matching tyre on the other side of the axle. Many cars also show the original size on a sticker inside the driver’s door frame, in the fuel filler flap, or in the handbook.
What the numbers and letters mean
Each part of the size describes one physical measurement or construction detail. This is how 205/55 R16 91V breaks down.
| Marking | What it means |
|---|---|
| 205 | Tyre width in millimetres, measured from sidewall to sidewall |
| 55 | Aspect ratio: the sidewall height as a percentage of the width |
| R | Radial construction, which is standard on modern car tyres |
| 16 | Rim diameter in inches, the wheel size the tyre fits |
| 91 | Load index, a code for the maximum load the tyre can carry |
| V | Speed rating, a code for the maximum speed the tyre is built for |
The aspect ratio trips people up. A 55 doesn’t mean 55 mm. It means the sidewall is 55% as tall as the tyre is wide, so a lower number means a shorter sidewall. Don’t mix them up.
The rim size has to match the wheel. A 16 inch tyre only fits a 16 inch wheel, and the width and profile also need to match what the vehicle was designed for, because they affect handling and clearance. Don’t guess the rim size.
TyreSafe and the British Tyre Manufacturers’ Association glossary both explain these markings in more detail.
Load index and speed rating
The 2 characters after the rim size tell you how much weight and how much speed the tyre is built for. Both are codes, read against a published table.
The load index is a number. On our example, 91 corresponds to 615 kg per tyre, according to the industry figures published by TyreSafe. It isn’t 91 kg, and it isn’t the weight of the whole car.
The speed rating is a letter. Each letter matches a maximum speed the tyre can sustain at its rated load. Industry advice is that replacement tyres should at least match the load and speed ratings the vehicle maker specified. If your van tyre has extra characters, read them out exactly as printed.
Why the size matters when you call
Giving us the full size up front helps us check availability and talk through your options. When you ring 07466 022007, message us on WhatsApp, or use the quote form, read the full string from the sidewall, plus the vehicle make and model. We come to you at the roadside, at a home or driveway, or at work. We’re open 24 hours, 7 days a week.
If the tyre needs replacing, our mobile tyre replacement Essex page covers that work. For planned mobile work at home, on a driveway or at a workplace in the county, see our page on mobile tyre fitting Essex. Drivers around Epping, Loughton and Theydon Bois can also look at emergency tyre replacement Epping.
While you’re looking at the tyre, check the tread. UK law requires a tread depth of at least 1.6 mm across the central 3 quarters of the breadth of the tread and around the entire circumference, as set out in the Highway Code annex on vehicle maintenance.
Key takeaways
The size is moulded on the sidewall in a format like 205/55 R16 91V. Width is in millimetres, the aspect ratio is a percentage, and the rim size is in inches.
Load index and speed rating are codes, and replacements should at least match the maker’s specification. Read the full string to us when you call.
When this is the wrong answer
Don’t stop to read your tyre size if you’re somewhere unsafe. Getting yourself and any passengers to a place of relative safety comes first.
The Highway Code guidance on breakdowns says to use hazard warning lights and to wear fluorescent or light coloured clothing in daylight, and reflective clothing at night or in poor visibility. Never stand between your vehicle and passing traffic. On a motorway, don’t put out a warning triangle. If you can’t get out of the vehicle safely, stay belted in and call 999.
Once you’re safe, you can call us without the size. Give us the make and model and we’ll take it from there. If the situation is pressing, our emergency tyre repair Essex page explains how to reach us. We’ll check availability when you get in touch, and when you call we’ll give you a rough arrival time.
Reading the sidewall is also the wrong source if the tyre isn’t the original fit. If a previous owner fitted a different size, use the door sticker or handbook instead.
Common questions
Where else can I find the size if the marking is worn or the tyre is buried?
Try the inner sidewall first.
If that face is also worn, read the matching tyre on the opposite side of the same axle, or use the sticker inside the driver’s door frame, the fuel filler flap, or the handbook, which usually lists the original size the vehicle was meant to wear.
Should both tyres on an axle be the same size?
Yes. Tyres on the same axle should match in size, and matching the type and tread pattern is sensible as well. Mixed sizes across an axle can upset handling and braking.
What if I can only read part of the size?
Send us what you’ve got, even if it’s only the width and rim diameter alongside the make and model, and we’ll tell you if we need anything else before we can advise you.
Can Emergency Tyres still help if I can’t read the size at all?
We can still try. Call 07466 022007 or fill in the free quote form, describe the vehicle and where you are, and we’ll check availability.
Sources
- TyreSafe guide to load index and speed markings on car tyres: https://www.tyresafe.org/tyre-advice/tyre-markings/car-tyre-load-and-speed-markings/
- BTMA glossary explaining common tyre size markings: https://btmauk.com/advice-about-tyres/glossary-of-tyre-terms/
- GOV.UK Highway Code annex on keeping tyres legal: https://www.gov.uk/guidance/the-highway-code/annex-6-vehicle-maintenance-safety-and-security
- GOV.UK Highway Code advice if you break down: https://www.gov.uk/guidance/the-highway-code/breakdowns-and-incidents-274-to-287