Rear cassette ‘slipping’…?

Now and again (im pretty certain…) the cassette almost slips, or moves a little, usually when pedalling quite hard. Obviously i have never seen it happen, but you get the feeling through the pedals and a loud crack when it does.

Is this the freehub body wearing out? Or freewheel mechanism? Im just worried one day it will slip completely with a painful result… 😯

Hub is XT, a few years old now but bearings are ok.

Advice appreciated.

I always thought that sound was the pawls going? So yes, freehub/freewheel could be on it’s way out?

Could either the a knackered freehub or the chain slipping perhaps??

Its definitely not the chain…

I had this problem. XT freehub was full of crap and was making the pawls miss the teeth. The clicking sound had been almost silent for months so that could be a tell tale sign. Clicking is back to near normal but I’ve not had it back as I’ve been using another wheel so I’m unsure if the problem is solved.

It’s not uncommon for shimano freehubs IME, and doesn’t bother me. I think it means a pawl is not 100% engaged and slips.

Forgive my ignorance, but what do the ‘pawls’ do? Are they serviceable, or a part of the freehub unit?

From Sheldon Brown: Pawl
A spring-loaded part that engages a set of teeth when moving in one direction, but slides over them when moving in the other direction. The pawls in a freewheel make a ticking sound when a bicycle coasts. Most freewheels have two or three pawls.

Best explained by looking at a Hope service diagram as they use external (to the freehub) pawls.

The shimano ones can be serviced but are not really designed to be – you get a spare freehub as a closed unit and bolt it back onto the hub. Hope ones can be dissembled and spares got for it.

If you do go the route of a new freehub, check the part number and you may find that it’s cheaper to get the freehub as part of a full cheap hub as opposed to a single part, and you then get a spare set of cones, bearings, axle, etc. as part of it.

FWIW I’ve had this on several hub which have lasted for ages afterwards

Excellent, thanks for the help lads 🙂

I have had it on 3 freehubs all of which failed dramatically shortly afterwards – on the tandem tho which does put more force thru them. I would replace asap. One nasty fall, one long walk home and one ruined ride was the results