Getting a clunking when I pedal hard, I think after freewheeling, e.g. undulating singletrack. Seems worse in some gears, not sure which. My BB was a bit worn so changed that. Measured chain and it doesn't seem stretched. Could it be: casette, rings, or (I hope not as Bike City serviced it in Oct) freehub?

It's your knees!

It would be guesswork by anybody without seeing the bike

Getting a clunking when I pedal hard, I think after freewheeling, e.g. undulating singletrack.

that suggests freehub – what's the hub?

Rear QR or bolt on dropout/deraileur hanger dirty or not tight enough?
Suspension pivot bearings?

Possibly your freehub is on its way out if it is after freewheeling as the ratchet teeth may be worn and missing their first attempt at meshing.

If it is a repetitive clunk at a specific point in every pedal stroke/revolution then it will be something else, possibly a loose crank that needs nipping up.

If its the crank and you have ridden with it like it for some time then you may have have knacked the crank and no amount to tightening will fix it. (based on square taper cranks in any case, not sure about all these new setups)

I'll check that QR dropout and cranks are tight. I have a horrible feeling it's the DT Swiss freehub that I had serviced just a few months back. It's annoying because I've barely ridded this bike since. I can feel a wheel rebuild coming on 🙁

What hubs are you using? Could be that the bearings holding the freehub are shot and causing the freehub body to shift as you pedal.

Otherwise, it could also be your cranks, what crankset are you using?

DT Swiss hub – the cheaper ones (380's?) and raceface ride crankset. The freehub felt a bit graunchy in the autumn so I got Jim from Bike City to strip and service it – reckoned it was OK.

I hear what you're saying about the bearings. If I grab the cassette it jiggles a bit. How much wobble is acceptable in the freehub body?

I'm not familiar with DT hubs, but it does sound like a loose bearing. There shouldn't be any play at all, otherwise your gear indexing would be thrown out. How's the shifting BTW?

As for the cranks, I had a set of Race Face Evolve XCs which wore at the splines causing a similar problem. I'm extremely wary of RaceFace cranks as a result.

Freehub body is too loose and I suspect the pawls aren't working right. I've left it with Bad Ass Bikes to fix up.

ta

I expect Bike city were trying to save you the expense of a new freehub body .I visited Bad Ass and was not impressed by the blokes attitude towards my request for info on 853 frames ,ie he knew sweet f a

i just swapped my dt wheel for a hope with dt rim cos the the freewheel was on the way out, mine was missing quite alot and couldnt be arsed with fixing it, so went for what i really wanted – a noisey hope! sounds sweet!

As for the cranks, I had a set of Race Face Evolve XCs which wore at the splines causing a similar problem.

Me too. Are the rides ISIS though, or ext.bb? Also, you could feel the feedback through the pedal as the splines slipped.

Was the cassette tightened correctly?

Also serviced in October ? thats a whole shitty wet winter to **** things up and wear parts out it probably needs servicing again

No reply then Buzz ,you finished slagging Jim and the shop off then?

Sounds like freehub, I have had exactly the same symptons on my halo spin dr rear hub which is a non serviceable ball race item. Only 20 quid on crc for a new on tho..