I am wondering if anyone has come across an issue with a freehub whereby the pawls don't fully engage until you apply some load to the pedal/s and then they engage with a loud clunk - sometimes...?
To put this into context I am experiencing a big clunk on occasion when I reapply load to the pedals after freewheeling. It could be that I've stopped at a junction and when I set off I get this loud "clunk". Or just freewheeling around a corner and then when I start to pedal - "clunk".
It doesn't happen all the time and it's not in any specific gear and it's become more frequent.
I have had the bike on a stand and I can sort of recreate the issue and when it occurs the drivetrain including the cassette shifts round about 5mm (sometimes it's less and with a less pronounced clunk) but the wheel does not move which is what is leading me to believe it is the freehub. I have checked some obvious things - axel fully tightened to correct torque and the cassette is not loose at all. The wheel spins completely freely and I can hear the pawls (or whatever) clicking as it spins like you would expect. I have not had the wheel in bits as I don't have the tools.
The wheel is one of these Shimano MT501 and the freehub is one of these I think Freehub
The Shimano info seems to suggest that the freehub body itself is a sealed unit and cannot be serviced anyway so needs replacing if it has failed I guess. However, from what I can tell the part number for the free wheel body itself seems to be Y0KD98040 but I cannot find it for sale anywhere. The bike is still under warranty but I am surprised that such an important part should have failed after such a short time (800 ish miles)which is making me wonder if it could be something else. The bike is an e-mtb btw....
I can obviously take it back to where I bought it but they are shut for the moment.
Thanks for any pointers....
I would check the pawls and make sure they are clean and not too much grease sound like they might be sticking
Cold conditions may have increased the lube viscosity to the point that the pawls aren’t moving freely enough.
As above, remove, clean and relube the freehub/pawls.
I've had this when I over greased a Hope Pro 2.
Clean pawls, light grease, refit.
@sillyoldman - I did wonder if it was perhaps temp related.
I don't think I can get at the pawls though. Shimano info suggests that the freehub itself should not be disassembled and I have been unable to find an exploded diagram.
Bottom of page 16 here Freehub
"Do not attempt to disassemble the freewheel body, because it may result in a malfunction"
The grease hasn't been touched since new though. Is it common for freehubs to do this in the cold? Does it need a different grease? Does the grease change its viscosity permanently when exposed to cold? I've been out in about -5 (windchill) but that's all. Shimano have a specific freehub lube also which I can't seem to find for sale anywhere either!
However, from what I can tell the part number for the free wheel body itself seems to be Y0KD98040 but I cannot find it for sale anywhere
They are currently out of stock with supplier until mid March(ish). I'm not sure I'd want to chuck a £60 freehub at a £100 wheel though. As you say it is in warranty then get the shop to look at it when they open.
@simondbarnes - any idea what the correct part number would be? I got that one off the Shimano tech doc for that wheel, https://si.shimano.com/api/publish/storage/pdf/en/ev/WH-MT501-CL-R12-B-29/EV-WH-MT501-CL-R12-B-29-4556.pdf.
That is the correct part number.
Thanks - So I would be better off buying a whole new wheel if this were to occur out of warranty then - good to know. Do you happen to know if the pawls are accessible anyway or is it sealed?
Do you happen to know if the pawls are accessible
Yeah, they are. Lube with Shimano freehub grease.
Thanks. Have you got a link to that video?
I haven't. It's part of the Shimano Tec training.
Ah! Lol!
Is mine like this do you think?
In that video it looks like a spring loaded mechanism with a locking ring rather than pawls but your pic deffo shows pawls.
I suppose the vid is of one 1000x the price of mine!!!!
Actually - one more question. Can I remove the freehub body without taking the axle out. ie just remove the cap and the outer seal then slide the freehub out?
Can I remove the freehub body without taking the axle out. ie just remove the cap and the outer seal then slide the freehub out?
Yeah. Pull the cap off with a 17mm cone spanner then pull the freehub off (seal will come off with it)
@simondbarnes - Thankyou so much. Obv simpler to take it to the dealer (which I will do as it's under warranty once they open again, but they are not a Shimano dealer just an ebike dealer). I'm interested in DIY maint also and I'm intrigued to see what could possibly be wrong with it. Mind you, by the time I have bought all the required tools I may as well have bought the whole wheel!!! lol
Anyway thanks again for the tips, Much appreciated. 🙂
I’d be surprised if the shop did not have a Madison ( shimano uk ) account.
But either way it’s the shops problem to sort out.
There's a Shimano dealer not far from me so at a push I guess I could ask them to sort it under warranty. Fingers crossed the dealer I bought it from will be able to sort anyway.
Thanks for all the replies. 🙂
It'll be one or more pawls/springs that are broken, the noise (normally its a sharp ping or crack) will be that 5mm movement of the freehub as one pawl slips and the next one catches the ratchet.
I dont think this is sticky pawls. It sounds suspiciously like a low POE hub which stock shimano are aren't they?
The clunk is the pawls being accelerated through the dead spot and then hitting the next tooth.
So I got the hub stripped and the pawls were sticking shut. Nothing broken thankfully as replacement parts are seemingly non-existent for a 12 speed microspline hub with open bearings. Not without buying a new freehub at £60 odd quid when the whole wheel is only £100, even then no one has any stock! 😮 Full clean, and regrease and all is good. 🙂 For info @simondbarnes the cap doesn't "pop off" on my version but unscrews like the rest of it. The Shimano manual from si.shimano.com which says it pops off must be for a better spec version than the one I have (even though the model number is correct).
