90/100 R21 tyres are available at the Rīgas Riepas online store, with prices starting from 45,00 €.
How to read a motorcycle tyre size
The size is on the sidewall. Unlike a car, a motorcycle usually takes different sizes front and rear, so it is worth writing down both before ordering.
Take 90/100 R21 57M as an example:
- 90 - section width in millimetres.
- 100 - aspect ratio as a percentage of the width, about 90 mm here.
- R21 - radial construction and rim diameter in inches. A dash instead (for example 3.00-18) means bias-ply, and a B means bias-belted.
- 57 - load index, equal to 230 kg per tyre.
- M - speed rating.
What else to look for
- M/C confirms the tyre is made for a motorcycle.
- TL is tubeless, TT needs an inner tube. TL/TT means it can be run either way, which is common on spoked rims.
- Front or Rear and an arrow show the fitting position and direction of rotation.
The load and speed ratings must not be lower than the motorcycle manufacturer specifies. Correct pressure comes from the owner's manual, not from the tyre maker.