18-inch off-road tyres for motocross, enduro and trial bikes, the rear size for enduro and trial bikes.
Choosing the right one
The diameter is on the sidewall: 90/90-21 means 21 inches. Pick the tyre for your terrain (hard, intermediate or soft such as sand or mud) and check the recommended width for your rim. Fit a new inner tube along with the tyre.
Brands available: MITAS, KENDA, DUNLOP, MICHELIN, METZELER and CONTINENTAL.