How to Read Tyre Sizes & Labels
Tyre Sizes & Markings Explained
The markings on your tyre sidewall and the sticker on a new tyre provide essential data on your vehicle’s safety, efficiency, and legality. This guide breaks down how to read your tyre size and understand the performance labels found on every tyre sold in the UK.
Understanding Your Tyre Sidewall Code
Decoding the Tyre Size
The most important code is the size, usually the largest set of numbers on the sidewall. Using 205/55 R16 as an example, here is the breakdown:
- Width (205): The first three digits are the tyre’s width in millimetres from sidewall to sidewall.
- Profile (55): The next two digits are the height of the sidewall as a percentage of the width.
- Construction (R): The letter "R" stands for Radial, the standard design for almost all modern cars.
- Diameter (16): The final number is the diameter of the wheel rim in inches.
Load Index & Speed Rating
Directly following the size, you will find a code such as 91V.
- Load Index (91): This numerical code represents the maximum weight capacity the tyre can support (615kg in this case).
- Speed Rating (V): This letter indicates the maximum safe speed for the tyre (149mph).
XL / Reinforced (Extra Load)
If your tyre size is followed by XL, it means "Extra Load." These tyres are designed to handle higher air pressures and more weight than a standard tyre of the same size. You will almost always see these on heavy SUVs, Estate cars, and Electric Vehicles (EVs) due to the weight of the batteries.
An Example
205/55 R16 79T
- 205 = width (mm)
- 55 = profile (%)
- R = radial construction
- 16 = rim diameter (inches)
- 79 = max load index
- T = speed rating
Understanding the Performance Label
New tyres feature a standardised label rating three key areas from A (Best) to E (Worst). This allows you to compare tyres on more than just price.
What Do The Ratings Mean?
Fuel Efficiency
Measures rolling resistance. 'A' rated tyres save significantly more fuel (or battery range) than 'E' rated ones.
Wet Grip
This is a vital safety rating for braking performance on wet roads.
Noise Rating
External road noise measured in decibels (dB). A lower number means a quieter environment outside the car.
QR Code
Modern labels (as of 2026) include a QR code in the top right corner. Scan this with your phone to see the full technical data sheet from the manufacturer.
Winter & All-Season Markings (3PMSF)
If you have all-season or winter tyres, look for these specific safety symbols:
- 3PMSF (Three-Peak Mountain Snowflake): This is the "Alpine" symbol—a snowflake inside a three-peaked mountain. It proves the tyre has passed legal tests for performance on packed snow and ice.
- M+S (Mud + Snow): This indicates the tread is designed for loose conditions. It is a manufacturer claim and does not necessarily mean the tyre is tested for extreme winter temperatures.
Ply Ratings: 6, 8, and 10 Ply (PR)
On vans, trailers, and 4x4 tyres, you may see a marking like 8PR or 10 Ply Rating. This measures the strength of the tyre's internal casing.
- 6-Ply (Load Range C): Common for small trailers and light vans.
- 8-Ply (Load Range D): The standard for most medium-sized vans (e.g., Ford Transit).
- 10-Ply (Load Range E): Heavy-duty tyres for large vans and 4x4s.
Note: If "Ply" isn't written, look for a C after the rim size (e.g., 195/70 R15C). The "C" stands for Commercial and indicates an 8-ply or 10-ply equivalent strength.
Unusual Markings & Special Exceptions
- Caravan & Motorhome (CP): Size codes ending in CP (e.g., 215/70 R15 CP) are reinforced for high, constant weight and to prevent "flat-spotting" during long storage periods.
- The "Old Format" Trailer Sizes: Small trailers often use an imperial (inch-based) format like 4.80-8. The first number is the width in inches, and the second is the rim diameter.
- ZR Markings: On high-performance tyres, you might see ZR (e.g., 225/40 ZR18). This is an older high-speed designation indicating capability over 149mph.
How to Check Tyre Age (DOT Code)
Look for a 4-digit code (e.g., 1026) usually found in a small oval on the sidewall.
- The first two digits (10) are the week of manufacture.
- The last two digits (26) are the year (2026).