MTB freehub bodies

How to choose your MTB freehub body

The freehub body is the part of the rear hub that holds the cassette and contains the engagement mechanism. It is replaced for two reasons: to switch from one cassette standard to another, or because it is worn.

The three standards

• Shimano HG : 8, 9, 10 and 11-speed cassettes, Shimano as well as SRAM.
• Micro Spline : Shimano 12-speed cassettes, with their small 10-tooth sprocket.
• SRAM XD : SRAM Eagle 12-speed cassettes. XDR is the longer version, intended for road and gravel.
• Changing the freehub body is usually enough to switch from one standard to another: the wheel itself does not change.

It depends on the hub, not the bike

Each manufacturer has its own interface: DT Swiss Ratchet, DT Swiss 3 Pawl, Mavic ID360, Shimano. Check the exact brand and model of your hub, as well as its generation — a DT Swiss Ratchet EXP body cannot be fitted to a standard Ratchet hub.

Engagement systems

• DT Swiss Ratchet : two opposing star ratchets, in 18, 36 or 54 teeth. Switching to 54 teeth divides the engagement angle / dead zone by three when pedalling.
• Pawls (3 or 6 PAWL): the pawls and their springs are the parts that wear out, and they can be replaced separately.
• Mavic ID360 : dedicated ratchet kit, specific to recent Mavic hubs.

When to replace it

• The splines are gouged by the sprockets, especially on aluminium bodies. The cassette develops play and shifting becomes inaccurate.
• The freehub slips under torque, typically when out of the saddle or accelerating.
• The mechanism is silent or seized : here, a simple clean and regrease is often enough.

Maintenance

Use a specific, low-viscosity freehub grease. A thick grease sticks pawls or star ratchets, especially in cold weather: the freehub no longer engages and the pedal spins freely. This is the most common breakdown in winter, and the easiest to avoid.

To find out more: How to choose a mountain bike cassette

See also: Mountain bike cassettes · MTB hubs · MTB bearings