Every tyre has its size moulded into the sidewall, and it tells you more than the size. Once you know how to read it, you can check that a new tyre fits your car, carries the load and is rated for the speeds you drive at. Here’s how it works, using a common size as the example.
The size code: 205/55 R16 91V
| Part | What it means |
|---|---|
| 205 | Tyre width in millimetres, measured across the tyre from sidewall to sidewall. |
| 55 | Aspect ratio. The sidewall height is 55% of the width, so about 113 mm here. A lower number means a shorter, stiffer sidewall. |
| R | Radial construction. Almost every car tyre sold today is radial. You may also see ZR on fast tyres, which marks a tyre rated for over 240 km/h. |
| 16 | Rim diameter in inches. The tyre only fits a 16-inch wheel. |
| 91 | Load index: the maximum weight each tyre can carry at its rated pressure. 91 is 615 kg. |
| V | Speed symbol: the maximum speed the tyre is rated for when correctly inflated and loaded. V is 240 km/h. |
On our product pages, the Available Sizes tab lists each size the same way, split into columns: rim, aspect ratio, tyre size, load index, speed symbol and XL or RF.
Load index table
The load index is per tyre, so a car with four tyres at load index 91 can carry up to 4 x 615 kg in total (the car’s own weight included). Never fit a tyre with a lower load index than your car’s maker specifies.
| Index | kg | Index | kg | Index | kg |
|---|---|---|---|---|---|
| 75 | 387 | 89 | 580 | 103 | 875 |
| 76 | 400 | 90 | 600 | 104 | 900 |
| 77 | 412 | 91 | 615 | 105 | 925 |
| 78 | 425 | 92 | 630 | 106 | 950 |
| 79 | 437 | 93 | 650 | 107 | 975 |
| 80 | 450 | 94 | 670 | 108 | 1000 |
| 81 | 462 | 95 | 690 | 109 | 1030 |
| 82 | 475 | 96 | 710 | 110 | 1060 |
| 83 | 487 | 97 | 730 | 111 | 1090 |
| 84 | 500 | 98 | 750 | 112 | 1120 |
| 85 | 515 | 99 | 775 | 113 | 1150 |
| 86 | 530 | 100 | 800 | 114 | 1180 |
| 87 | 545 | 101 | 825 | 115 | 1215 |
| 88 | 560 | 102 | 850 | 116 | 1250 |
Speed rating table
| Symbol | Max speed | Symbol | Max speed |
|---|---|---|---|
| N | 140 km/h | T | 190 km/h |
| P | 150 km/h | H | 210 km/h |
| Q | 160 km/h | V | 240 km/h |
| R | 170 km/h | W | 270 km/h |
| S | 180 km/h | Y | 300 km/h |
The letters aren’t in alphabetical order once you pass T: H sits between T and V. A speed rating is a tested maximum, not a target. It also tells you how the tyre is built, because higher-rated tyres are usually stiffer and sharper to steer.
What XL and RF mean
XL stands for Extra Load. An XL tyre has a stronger construction, so it can carry more weight than a standard tyre of the same size, as long as it’s pumped to the higher pressure it needs. Heavier cars, SUVs and some EVs often need XL tyres from the factory. RF stands for Reinforced, and in size tables like ours it means the same thing as XL.
Don’t mix up RF with run-flat. Run-flat tyres, which let you drive a short distance after a puncture, use their own brand markings such as RFT, ROF, SSR or ZP. If your car came on run-flats, replace them with run-flats.
How to read the DOT date code
Look for the letters DOT on the sidewall, followed by a string of letters and numbers. The last four digits are the date the tyre was made: the first two are the week and the last two are the year. So 2524 means week 25 of 2024. A tyre with only three digits there was made before 2000 and is long overdue for replacement.
Rubber hardens with age, even when the tread still looks deep. Check the date when you buy new tyres, and when you look at a spare that’s never been used.
How to find your tyre size
- Read the sidewall of the tyres on your car now. The size is the code that looks like 205/55 R16 91V.
- Check the tyre placard, usually a sticker on the driver’s door frame (sometimes inside the fuel flap). It shows the factory size and the recommended pressures.
- Look in the owner’s manual. Some cars allow more than one size, for example a different size for 17-inch wheels.
If the tyres on your car don’t match the placard, someone may have changed them before. Go by the placard, or ask a tyre shop to check.
Tyre size FAQ
Sometimes, but only within limits. The overall diameter has to stay close to the original, or the speedometer, ABS and stability control will read wrong. Changing width or aspect ratio is a job for a tyre shop to check, not a guess.
It’s best not to. Your car maker picked the speed rating for the car’s top speed and handling. Fitting the same rating or higher is the safe choice.
If your placard or current tyres show XL, or a load index that only an XL tyre in that size can meet, then yes. Check the load index in our size tables against the number on your placard.
It marks a tyre rated for speeds over 240 km/h. You’ll still find the actual speed symbol, such as W or Y, after the load index.
Look for the tread wear indicators, small raised bars inside the main grooves set at 1.6 mm. When the tread is level with them, the tyre needs replacing. Also replace a tyre with cracks, bulges or cuts in the sidewall, and check the DOT date on older tyres.
Tyres on the same axle should always be the same size, brand and model. Four matching tyres is best. If you only replace two, fit the new pair on the rear axle, which helps keep the back of the car stable on wet roads.