Road freehub bodies

How to choose your freehub body

The freehub body is the part of the rear hub that the cassette slides onto. You need to meet two criteria at the same time : the cassette standard, and the hub's brand and generation.

The cassette standard

• Shimano HG : the most common, compatible with 8- to 11-speed road cassettes and Shimano 12-speed road cassettes.
• SRAM XDR : specific to SRAM 12-speed road cassettes. It is 1.85 mm longer than the MTB XD version, and the two are not interchangeable.
• Campagnolo : brand-specific splines, for 9- to 12-speed cassettes.
• Micro Spline : originally a Shimano 12-speed MTB standard, found on some road and gravel wheels.

The hub matters as much as the cassette

An HG body for a DT Swiss hub will not fit a Mavic hub, even if the cassette standard is identical. Each manufacturer has its own interface: Mavic FTS-L, ITS-4 and ID360; DT Swiss Ratchet, Ratchet EXP and 3-Pawl; then Fulcrum, Campagnolo, Zipp Cognition, Enve InnerDrive. Note the hub model number before anything else.

The mechanism's wear parts

• Pawls and springs : they wear, seize up and eventually slip under load. They can be replaced separately for a fraction of the price of a complete body.
• DT Swiss ratchets : Ratchet kits come in 18 and 36 teeth, and moving from 18 to 36 doubles the number of engagement points.
• Mavic ID360 kits : the same principle applies, and they can be fitted without a special tool.
• A freehub body that slips is more often caused by dirty pawls or grease that's too thick than by a body that needs replacing.

Spacers

Fitting a 10- or 11-speed cassette to a body designed for 11 or 12 speeds requires a spacer. It sometimes comes with the cassette, but often doesn't. It's the part you find yourself missing on fitting day.

To find out more: How to choose your road bike cassette

See also: Road cassettes · Road hubs · Road disc wheels