The most important line on the sidewall
Every car tire carries dozens of characters. The most important ones are combined in a single line, for example <strong>205/55 R16 91V</strong>. If you can read this line, you know which tire fits your car, how much it may carry and how fast you may drive on it. You will also find the figures in your vehicle papers, inside the fuel filler flap or on the driver's door pillar.
Width, aspect ratio, construction, rim size
- 205 is the tire width in millimetres, measured from sidewall to sidewall. Common car widths range from 155 to 315 mm, always in steps of 10 ending in 5.
- 55 is the aspect ratio. The sidewall height is 55% of the width, here 112.75 mm. The smaller the number, the lower the profile.
- R stands for radial construction. The carcass cords run across the direction of travel. Almost all modern car tires are built this way.
- 16 is the rim diameter in inches. One inch is 25.4 mm.
From these values the tire size calculator works out the overall diameter, circumference and revolutions per kilometre. If there is a Z in front of the R, such as 225/40 ZR18, the tire is built for speeds above 240 km/h.
The load index
The number after the size, here 91, is the load index. It encodes the maximum load per tire at the correct pressure. The values follow an international table:
| Index | kg | Index | kg | Index | kg |
|---|---|---|---|---|---|
| 80 | 450 | 88 | 560 | 96 | 710 |
| 82 | 475 | 89 | 580 | 97 | 730 |
| 84 | 500 | 91 | 615 | 98 | 750 |
| 85 | 515 | 92 | 630 | 100 | 800 |
| 86 | 530 | 94 | 670 | 103 | 875 |
| 87 | 545 | 95 | 690 | 105 | 925 |
Four tires with index 91 carry 2,460 kg together. The index of your new tires must be at least as high as stated in your vehicle papers. A higher index is always allowed. Reinforced tires are marked XL, Extra Load or Reinforced. The complete table from 60 to 125 is in the calculator.
The speed rating
The letter at the end gives the tire's maximum permitted speed:
| Symbol | km/h | Symbol | km/h |
|---|---|---|---|
| Q | 160 | H | 210 |
| R | 170 | V | 240 |
| S | 180 | W | 270 |
| T | 190 | Y | 300 |
Note that H is out of alphabetical order. It sits between U (200 km/h) and V (240 km/h). Again, the tire must have at least the rating stated in the papers. The only exception is winter tires. In Germany they may have a lower rating if a sticker or display in the driver's field of view shows the permitted maximum speed.
Other markings on the sidewall
- DOT code: the last four digits show the production week and year. More in Tire age from the DOT code.
- E mark: an E with a number in a circle confirms approval under UN rules, ECE R30 for car tires.
- Alpine symbol: a mountain with a snowflake. Only such tires meet Germany's winter tire rule.
- M+S: mud and snow. Since October 2024 this marking alone is no longer enough in Germany.
- TWI: marks the tread wear indicators in the grooves, which become visible at 1.6 mm of remaining tread.
- Rotation arrow: on directional tires it shows the direction of rotation when driving forwards.
Where does it say which size is allowed?
The German registration certificate usually lists just one tire size. That does not mean only this size is allowed. The full list of approved sizes is in the EC certificate of conformity, known as the CoC. If you cannot find it, ask the manufacturer or a specialist garage. Sizes not listed there need a type approval or an expert report. How far an alternative deviates from the original is covered in the main guide Tire size explained.
In short
205/55 R16 91V means: 205 mm wide, sidewall 55% of that, radial tire, 16-inch rim, 615 kg load capacity, up to 240 km/h. Load index and speed rating must at least match the values in your papers. Enter the size in the tire size calculator to see its diameter and circumference and compare alternatives.