The first step in changing a tyre is knowing the right size. The size is embossed on the tyre sidewall as a string of digits and letters.
The parts of the string
- 120 — width in millimetres. The widest point of the tyre.
- 70 — aspect ratio as a percentage. Sidewall height relative to width; 70 means "the sidewall is 70% of the width".
- ZR — construction. R is radial, ZR is radial rated for high speed; no marking means a bias (diagonal) carcass.
- 17 — rim diameter in inches.
- 58 — load index. The code for the maximum weight the tyre can carry.
- W — speed index. The letter for the maximum speed rating.
Front and rear are not the same
On most motorcycles the front and rear tyres are different sizes. Read them separately; ordering a front tyre based on the rear marking is the most common mistake.
Inch sizes
Some tyres have no aspect ratio: you will see a string such as 3.50-10. These are inch sizes and simply do not have that part; width and rim diameter are enough.
If you cannot read the size
Our tyre finder lets you narrow the catalogue by width, aspect ratio and rim. If you cannot read the marking, typing the sidewall text of your current tyre works just as well.