The freehub isn’t part of the drivetrain, but replacing a worn cassette will involve correctly mounting new sprockets upon it.
Andy warns of the need to install a spacer ‘behind’ the cassette on wheelsets where such is required (the recently tested Swiss Side Franc, and the newly-arrived Mavic Aksium, to name but two). Failure to do so could lead to the cassette damaging the hub, in extreme cases.
At the other end of the cassette, Andy advises to check the tightness of the lockring after a first ride. “They can ‘settle’,” he says. An excessively loosened lockring would allow the smallest sprocket to fall off the freehub and damage the frame.
Freehub bodies are highly unlikely to suffer excessive wear. Aluminium bodies are likely to be marked by the pressure of a steel cassette, but such ‘damage’ typically is cosmetic only. Some, higher quality wheelsets have a lightweight steel freehub body. Additionally, higher quality cassettes will contain a ‘carrier’ for some if not all of the sprockets. The Shimano 105 cassette pictured on the previous page has an alloy ‘carrier’ for the three largest sprockets. The remaining seven are individual units, separated by plastic spacers.