368/97 V.A.R. Freewheel Body Vice

It’s a small component we tend to take for granted, but the freehub is an essential part of most bikes and does a vital job. The freehub transmits your pedal power to the road or trail and gives your legs a rest while you’re still moving.

For many riders, it’s a case of fit and forget, but there’s a lot going on with your freehub. It’s got some tricky mechanical parts that are hidden away inside it, which will sometimes need a little tender loving care to keep them working well.

If you always swap like for like when replacing your bike’s cassette, you may not need to worry much about freehub compatibility, but that too is trickier than it seems.

We’ll start off by explaining the different types of freehub and how their internals work, then later look at freehub standards and cassette compatibility.

Most bikes allow you to stop pedalling but keep moving, or “coast”. For bikes equipped with derailleur gears, that’s usually thanks to a freehub.

The freehub is an extension of the right-hand side of the rear wheel’s hub.

It contains a system that engages with the wheel when you’re pedalling, to propel you forward, and which disengages when you stop pedalling so that the wheel continues to turn without the gears and pedals turning. There’s a mechanism within the freehub body that engages and disengages the wheel from the gear sprockets.

On its outer surface, a freehub has a set of splines, onto which the cassette (i.e. the gear sprockets) is slid when a bike is assembled. In general, the cassette comprises a set of individual sprockets or clusters of sprockets.