Every tyre carries its whole specification moulded into the sidewall — the size, how much weight it can carry, how fast it is rated for, when it was made and which approvals it holds. Once you can read it, buying the right replacement and setting the correct pressures becomes much simpler. This guide decodes every marking in plain language and gives you the full load-index and speed-rating tables to look up your own tyre.
Decoding a tyre size: 205/55 R16 91V
The main size code looks intimidating but each part is simple. Taking 205/55 R16 91V as an example:
- 205 — the tyre width in millimetres, tread to tread.
- 55 — the aspect ratio: the sidewall height as a percentage of the width. Here the sidewall is 55% of 205 mm. A lower number means a shorter, sportier sidewall.
- R — radial construction, which almost every modern car tyre uses.
- 16 — the rim diameter in inches that the tyre is designed to fit.
- 91 — the load index, a coded figure for the maximum weight the tyre can carry (see the table below).
- V — the speed symbol, the maximum speed the tyre is rated for.
You may also see an XL or Reinforced marking. This means the tyre is built to carry a higher load at a higher inflation pressure than a standard tyre of the same size — common on heavier cars and EVs. If your car came with XL tyres, replace them with XL, and use the higher pressures on the door label.
Load index table (index → kilograms)
The load index is per tyre. Always fit a replacement with a load index equal to or higher than the original — never lower.
| Index | kg | Index | kg | Index | kg |
|---|---|---|---|---|---|
| 50 | 190 | 75 | 387 | 100 | 800 |
| 51 | 195 | 76 | 400 | 101 | 825 |
| 52 | 200 | 77 | 412 | 102 | 850 |
| 53 | 206 | 78 | 425 | 103 | 875 |
| 54 | 212 | 79 | 437 | 104 | 900 |
| 55 | 218 | 80 | 450 | 105 | 925 |
| 56 | 224 | 81 | 462 | 106 | 950 |
| 57 | 230 | 82 | 475 | 107 | 975 |
| 58 | 236 | 83 | 487 | 108 | 1000 |
| 59 | 243 | 84 | 500 | 109 | 1030 |
| 60 | 250 | 85 | 515 | 110 | 1060 |
| 61 | 257 | 86 | 530 | 111 | 1090 |
| 62 | 265 | 87 | 545 | 112 | 1120 |
| 63 | 272 | 88 | 560 | 113 | 1150 |
| 64 | 280 | 89 | 580 | 114 | 1180 |
| 65 | 290 | 90 | 600 | 115 | 1215 |
| 66 | 300 | 91 | 615 | 116 | 1250 |
| 67 | 307 | 92 | 630 | 117 | 1285 |
| 68 | 315 | 93 | 650 | 118 | 1320 |
| 69 | 325 | 94 | 670 | 119 | 1360 |
| 70 | 335 | 95 | 690 | 120 | 1400 |
| 71 | 345 | 96 | 710 | 121 | 1450 |
| 72 | 355 | 97 | 730 | 122 | 1500 |
| 73 | 365 | 98 | 750 | 123 | 1550 |
| 74 | 375 | 99 | 775 | 124 | 1600 |
Speed rating table (symbol → max speed)
The speed symbol is the top speed the tyre is certified to sustain. Fit a replacement rated at least as high as the original.
| Symbol | km/h | mph |
|---|---|---|
| L | 120 | 75 |
| M | 130 | 81 |
| N | 140 | 87 |
| P | 150 | 93 |
| Q | 160 | 100 |
| R | 170 | 106 |
| S | 180 | 112 |
| T | 190 | 118 |
| U | 200 | 125 |
| H | 210 | 131 |
| V | 240 | 150 |
| W | 270 | 168 |
| Y | 300 | 187 |
| ZR | over 240 | over 150 |
The rating applies to the tyre in good condition, correctly inflated and within its load limit. A higher-rated tyre is fine to fit; a lower-rated one is not.
The DOT code and how to read the age
Near one edge you will find a DOT code ending in four digits — the production date. The first two digits are the week and the last two are the year. For example, 1510 means week 15 of 2010. Tyres age even unused, so it is worth checking the date on “new” stock and on a car that has stood for years.
The E-mark (European type approval)
A small E or e inside a circle, followed by a number, shows the tyre holds European type approval and which country’s authority granted it — for instance E4 is the Netherlands. The longer number after it is the approval reference. It simply confirms the tyre is road-legal in Europe.
Run-flat and original-equipment markings
Extra letters near the size often flag a run-flat tyre (one that can be driven on for a limited distance after a puncture) or an original-equipment fitment tuned for a specific car maker. Each brand uses its own code:
| Marking | Meaning |
|---|---|
| RFT / ROF | Run-flat tyre / Run On Flat (general run-flat terms) |
| SSR | Self-Supporting Runflat (Continental) |
| DSST | Dunlop Self-Supporting Technology |
| EMT | Goodyear Extended Mobility |
| ZP | Michelin Zero Pressure |
| RSC | Runflat System Component (BMW/Mini fitment) |
| CS / CSR | Continental ContiSeal / Conti Safety Rim |
| HRS | Hankook Runflat System |
| MOE / AOE | Mercedes / Audi original-equipment extended (run-flat) |
| * (star) | BMW original-equipment approval |
| MO | Mercedes-Benz original equipment |
| AO / RO1 | Audi / Audi Quattro original equipment |
| N0–N4 | Porsche original equipment |
If your car left the factory on a run-flat or a maker-approved tyre, it is best to stay with the same type — the car’s suspension and (for run-flats) the absence of a spare are matched to it.
Which number sets your tyre pressure?
One common mistake is inflating to the big pressure figure moulded on the sidewall. That number is the tyre’s maximum, not the recommended running pressure. The correct figure comes from your car, on the label in the driver’s door jamb or the fuel flap — and it changes if you fit a different size or load rating.
- Fitted a non-standard size? Recalculate with our non-stock tyre pressure calculator.
- Comparing two sizes before you buy? Use the tyre size comparison & speedometer-error calculator.
- Label in the wrong units? The tyre pressure converter swaps bar, PSI and kPa instantly.
Frequently asked questions
Can I fit a tyre with a higher load index or speed rating?
Yes. Higher is always safe. Never go lower than the original on either figure, or you exceed the tyre’s rated capability.
What does the 91V at the end of my tyre size mean?
91 is the load index (615 kg per tyre) and V is the speed symbol (rated to 240 km/h). Both are look-up codes — see the tables above.
How old is too old for a tyre?
Many manufacturers suggest replacing tyres around 6–10 years old regardless of tread, because rubber hardens with age. Read the age from the four-digit DOT date code.
Do I have to use XL tyres if my car came with them?
Yes — XL (reinforced) tyres carry more load at higher pressure. Match the original and set the higher pressures listed on the door label.
Want the numbers behind the letters? Our tyre-pressure cluster goes deeper on the load index, the speed rating and XL vs standard tyres, and every guide ties back to the calculators above.
