On the sidewall of a motorcycle tyre there is a row of digits and letters: something like 120/70 ZR17 M/C (58W) TL. This code tells you the tyre's width, sidewall height, construction, rim diameter, the load it can carry and the highest speed it can withstand. Fitting the wrong size or a low-rated tyre when changing tyres causes problems for handling, safety and insurance. In this guide we explain, with examples, what every mark on the sidewall means. To type in your own tyre code and decode it instantly, use the tyre size reading tool.
Example: 120/70 ZR17 M/C 58W TL
| Mark | Meaning |
|---|---|
| 120 | Tyre width, in millimetres |
| /70 | Aspect ratio: sidewall height is 70% of the width, i.e. about 84 mm |
| Z | Old-style speed mark for speeds above 240 km/h |
| R | Radial construction |
| 17 | Rim diameter, in inches |
| M/C | Motorcycle tyre (motorcycle) |
| 58 | Load index: 236 kg |
| W | Speed rating: 270 km/h |
| TL | Tubeless, for use without an inner tube |
The rear tyre of the same motorcycle might be, for example, 180/55 ZR17 73W: 180 mm width, sidewall 55% of the width, 17-inch rim, load index 73 (365 kg) and speed rating W.
Width and aspect ratio
Width is the tyre's measurement in millimetres from sidewall to sidewall. The aspect ratio is the ratio of sidewall height to width. The difference between 180/55 and 180/60 may look small, but the sidewall height changes by about 9 mm; this affects the rear height of the motorcycle and therefore the steering geometry. Switching to a size not specified in the manual can change the motorcycle's turning character. On some motorcycles the manufacturer approves alternative sizes; check this in the owner's manual or the registration information.
On older types and some small motorcycles, the width is written in inches: for example 3.00-18 or 2.75-17. Here the first number gives the approximate width in inches and the second the rim diameter.
Construction: radial or cross-ply?
- R (radial): the plies are laid perpendicular to the tyre's centre. More flexible sidewall, a wider contact patch, less heating at high speed. Standard on mid- and large-capacity motorcycles.
- - or no letter (cross-ply, bias): the plies are laid diagonally. Stiffer sidewall, high load-carrying capacity, cheap. Common on small motorcycles, scooters and some custom motorcycles.
- B (bias belted): between the two; on some cruisers and touring motorcycles.
Mixing radial and cross-ply tyres on the same motorcycle is generally not recommended. Use the same construction front and rear unless the manufacturer allows otherwise.
Load index table
The load index shows the greatest load the tyre can carry at the stated pressure. On a motorcycle the front and rear tyres have different indexes; the rear tyre carries most of the rider, passenger and luggage.
| Index | Kg | Index | Kg |
|---|---|---|---|
| 48 | 180 | 62 | 265 |
| 51 | 195 | 65 | 290 |
| 54 | 212 | 69 | 325 |
| 55 | 218 | 71 | 345 |
| 57 | 230 | 73 | 365 |
| 58 | 236 | 75 | 387 |
| 59 | 243 | 78 | 425 |
The load index of the new tyre must not be lower than that of the original tyre. A higher index is not a problem.
Speed rating table
| Letter | Maximum speed | Letter | Maximum speed |
|---|---|---|---|
| J | 100 km/h | S | 180 km/h |
| K | 110 km/h | T | 190 km/h |
| L | 120 km/h | H | 210 km/h |
| M | 130 km/h | V | 240 km/h |
| N | 140 km/h | W | 270 km/h |
| P | 150 km/h | (W) | Above 270 km/h |
| Q | 160 km/h | Y | 300 km/h |
If the speed rating is in brackets, for example (W), the tyre can exceed 270 km/h; the upper limit is written in the tyre manufacturer's documentation. The ZR mark on its own indicates suitability for above 240 km/h. The speed rating of the new tyre must not be lower than the original; even if the motorcycle's top speed is lower, keep the rating the manufacturer approved.
DOT code and production date
On the tyre sidewall there is a code starting with "DOT". The four-digit number at the end of this code shows the week and year the tyre was made:
- 2423: the 24th week of 2023, i.e. mid-June.
- 0526: the 5th week of 2026, i.e. early February.
The four-digit date is sometimes written separately from the rest of the code, in a small oval, and appears on only one sidewall of the tyre. If you cannot see it, look at the other sidewall. When buying a new tyre, ask for the DOT date; a tyre that has sat in a warehouse for a long time may be new on paper, but its rubber has begun to age. We explain in detail when a tyre should be changed in the tyre replacement guide.
Other marks
- TL / TT: TL is for use without an inner tube (tubeless), TT is with an inner tube (tube type). Many motorcycles with spoked wheels use TT tyres; if a TL tyre is to be fitted to a motorcycle whose rim is not tubeless, an inner tube is used too.
- Rotation arrow: the tyre must be fitted so that it rotates in this direction. The front and rear tyres' arrows are different; on some tyres "front" and "rear" is written.
- Front / Rear: front and rear tyres have different construction and cannot be swapped.
- TWI or triangle mark: shows the position of the wear indicator. When the tread wears down to the level of the indicator, the tyre must be replaced.
- E mark and number: shows the tyre's European type approval.
- Max. load / Max. press: the greatest load the tyre can carry and the inflation limit. This value is not the recommended riding pressure; the correct pressure is written in the motorcycle's manual or on the label on the swingarm.
Checklist when buying tyres
- Is the size the same as the value in the manual or on the registration document?
- Are the load and speed ratings no lower than the original?
- Is the construction (radial or cross-ply) compatible front and rear?
- TL or TT, is it suitable for your rim?
- Is the DOT date recent?
- Are the front and rear the same model? Using mixed models can upset the balance of grip.
Price ranges and standout models are on the motorcycle tyre page. Carrying a tyre repair kit for a puncture on the road is also a good idea.
Scooter and small motorcycle tyres
On scooters and small motorcycles the tyre codes can look a little different. For example, in a code like 110/70-13 the dash indicates cross-ply construction and 13 is the small rim diameter. Tyres on small rims rotate faster and heat up sooner; so following the speed rating and pressure values is important on these motorcycles too. On some scooters the front and rear tyres are the same size but their construction and rotation directions differ; do not fit the front tyre on the rear. On small motorcycles with spoked wheels, TT use, that is with an inner tube, is common; in a puncture the inner tube has to be replaced, and a plug-type repair does not work on an inner tube.
When choosing tyres, think about the type of use too: for mostly city and rain use, tyres with high wet-surface performance and plenty of tread; for long distance, durable dual-compound touring tyres; for off-road, knobbly enduro tyres. On adventure motorcycles, the ratio of off-road to asphalt use is decisive in tyre choice. If you are undecided, look at the type of your motorcycle's original tyre and the approved list in the manual.
Conclusion
The code on the tyre sidewall tells you the width, sidewall height, construction, rim diameter, and load and speed limits; the DOT code tells you its age. When buying a new tyre, compare the size against the manual, do not lower the ratings and be sure to ask for the production date.
Frequently asked questions
What does 120/70 ZR17 mean?
It means the tyre is 120 mm wide, its sidewall height is 70% of the width, it has radial construction, it is suitable for above 240 km/h and it fits a 17-inch rim.
How can you tell the tyre's age from the DOT code?
The four digits at the end of the code show the week and year. 2423 says it was made in the 24th week of 2023.
Can I fit a wider rear tyre?
Only if the manufacturer has approved that size. A wider tyre may not seat fully on the rim, can change the motorcycle's turning character and can touch the chain or swingarm.
Can a tyre with a lower speed rating be fitted?
It is not recommended. The speed and load ratings of the new tyre must not be lower than those of the original tyre.