How to read a motorcycle tyre sidewall
A motorcycle tyre reads like 180/55 ZR 17 M/C (73W) TL. That is 180mm wide, with a sidewall 55 per cent of that width, radial construction rated beyond 168mph, on a 17 inch rim, for motorcycle use only, carrying up to 387 kilos at up to 168mph, tubeless. Every part of it has to match or exceed what your machine was approved on.
The size, part by part
180 is the section width in millimetres across the widest part of the inflated tyre.
55 is the aspect ratio, a percentage of the width rather than a measurement. A 180/55 has a sidewall about 99mm tall.
ZR or R is the construction. R means radial. ZR means radial and rated beyond 168mph, and it is a hangover from an older system that survives on fast machines. A dash instead of a letter means crossply, which is still normal and still correct on small scooter wheels.
17 is the rim diameter in inches.
The bits after the size
M/C means motorcycle use only. It is there to stop a car tyre of the same nominal size being fitted to a bike, which sounds unlikely and has happened.
The number in brackets is the load index and the letter after it is the speed rating. 73 is 387 kilos per tyre; W is 168mph. On an electric machine the load index is the figure to watch, because battery packs have made these vehicles heavier than the petrol bikes they replaced.
TL means tubeless and TT means tube type. Fitting a tube inside a tubeless tyre is done, and it lowers the speed rating. Fitting a tubeless tyre to a spoked rim without a sealed bed does not work at all.
The arrow, and why it matters more here
Almost every motorcycle tyre is directional and the arrow on the sidewall shows which way it must rotate. Front and rear arrows are frequently opposite, because the front is designed for braking loads and the rear for driving ones.
Fitting one backwards is not a subtle mistake on a motorcycle. It changes how the tread clears water and how the carcass behaves under load.
How old is it
The DOT code ends in four digits. Those are the week and the year of manufacture, so 2225 is the twenty-second week of 2025.
Rubber ages whether or not it is ridden, and a machine that sits through winter ages its tyres without wearing them. On a bike this matters more than on a car, because there are only two contact patches and no fourth wheel to keep you upright when one lets go.
Common questions
- What does the M/C marking mean?
- Motorcycle use only. A tyre without it was not built for a motorcycle, whatever size is printed on it.
- Is ZR better than R?
- Not better, faster. ZR is rated beyond 168mph. If your machine does not go that fast, R with the right speed letter is entirely correct.
- Can I fit a tube in a tubeless tyre?
- It is done on spoked wheels, and it reduces the speed rating. Check what your manufacturer allows before you do it.
Last checked 2026-09-22. Where this page and your own vehicle disagree, the vehicle wins.