Cassette Type Hubs

A freehub body is screwed into the hub, the freehub body has a series of straight splines which the sprockets slide onto and are retained on the freehub by means of a screwdown lockring .The sprockets are commonly sold as a set, called a "cassette". When the sprockets need to be replaced or the user wishes to replace them to change gear ratios, only the sprockets are replaced not the ratchet mechanism. To remove the cassette you will need to undo the lockring whilst holding the cassette in place with a chain whip, Freehub bodies can be removed and replaced with an 10mm allen key (in most cases) that inserts down the centre of the freehub once the axle has been removed. Dura-Ace bodies require a special spline wrench,

It is always advisable to change both your chain and cassette at the same time