TRANSMISSIONS

Number of speeds

• 1x12: today's standard, with a single chainring and a 10-51 to 10-52 tooth cassette.
• 1x11 and 1x10: still very common, with cheaper parts.
• 2x11 and 2x10: two chainrings for closer gear steps, mainly in cross-country and on older MTBs.

The shifter, rear derailleur, cassette and chain must all have the same number of speeds.

Shimano or SRAM?

• Shimano HG: cassettes up to 11-speed.
• Shimano Microspline: Shimano 12-speed cassettes.
• SRAM XD: SRAM Eagle 12-speed cassettes.

The two brands cannot be mixed in 12-speed: a Shimano shifter will not operate a SRAM derailleur. The cassette also depends on your wheel's freehub body, listed above.

The crankset

• Crank length: usually 170 or 175 mm, 165 mm for smaller riders and MTBs with a low bottom bracket.
• Bottom bracket: threaded BSA, PF92, BB92 or BB386EVO depending on the frame. The standard is listed in the frame specifications.
• Chainring: 30 to 34 teeth on a 1x drivetrain; smaller for climbing, larger for speed.

Our FSA and Shimano cranksets are often sold without a bottom bracket: look for “w/o BB” on the product page.

When to replace the chain and cassette

A worn chain wears out the cassette and chainrings. Check it with a chain wear indicator every 1,000 to 1,500 km: replacing it in time often lets you keep the cassette. If the chain skips on a new cassette, both were worn.

E-MTB

Bosch motors (Active Line, Performance Line, Performance Line CX) and Shimano STEPS are replaced like for like: check the generation, assist speed (25 km/h in Europe) and system. Choose reinforced chains and cassettes for e-bikes.

Frequently asked questions

See also: MTB wheels · MTB brakes · Road drivetrain