If you look on the sidewall of your tyres you’ll see the tyre size. It will look like this example – 185/65R15/79H
The first section, 185 in this example, refers to the width, 185 mm.
The next, 65R15, refers to the Aspect ratio / Construction and Diameter. In our example …
- 65 the tyre would have a height equal to 65% of the tyre’s width. This number is often referred to as the tyre profile.
- R stands for radial and almost all tyres manufactured today will be radial tyres.
- 15, is the inner diameter of the tyre rim in inches. 15 inches.
79H.
- 79 represents the load rating, which is the maximum weight the tyre can carry in kg, assuming the tyre is correctly inflated.
- H represents a speed rating, which is the maximum speed that the tyre can handle while under load. The letter will vary, often between Q and Y. In this example, H means that the maximum speed is 130 mph. Other letters are as follows:
| Code | mph |
|---|---|
| Q | 100 |
| R | 106 |
| S | 112 |
| T | 118 |
| U | 124 |
| H | 130 |
| V | 149 |
| Z | Over 149 |
| W | 168 |
| (W) | Over 168 |
| Y | 186 |
| (Y) | Over 186 |