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my bike is slipping in the 3 hardest gears whenever I apply any moderate power, It's been doing this for quite a while and getting worse. Unrelated I recently snapped my mech hanger so that's been replaced and I've tried it with another derailleur and same issue so can rule out those issues.
I know the usual culprit is the cassette being worn but it looks visually in really good nick, isn't too old and shifts perfectly. also surely it would wear out in the lower gears quicker. just don't want to buy a new cassette for the issue to still occur.
Any thoughts? is this something a broken freehub would do or would it just not engage anymore and therefore it's definitely the cassette? - Sorry for wall of text but its been really annoying me and makes the downs not quite as fun so want to get to the bottom of it.
It doesn't really sound like a free hub issue, but it does sound a lot like you've a worn chain, and possibly cassette.
Just t confirm, when you say hardest gears, you mean the smallest cogs in the cassette, right?
This is where a worn chain is most likely to slip, as there are relatively few teeth engaging the chain.
Suggest to buy a chain checker and look at the wear on the chain,
https://www.chainreactioncycles.com/park-tool-chain-checker-cc-3-2/rp-prod5784
but I would recommend new chain, cassette and front chainring. When you've got to the point of things slipping, it usually indicates wear levels that require replacement of those three things.
Chain checker also a good thing to have to stay on top of chain wear before it causes problems.
Yeah the smallest cogs - I specifically said hardest gear rather than highest or lowest after the other thread about the right and wrong and thought it would be least confusing haha
Thats a good sign to be honest thanks - I'm happy to replace cassette and chain if need be but just didn't want to do that if it was actually another problem
👍
And yes, I share the confusion in my own head about moving up and down, bigger smaller etc etc 🙃
Agree that it's probably the cassette. If you've got a worn chain you previously removed, it might be worth putting it back on as you'll get a load more life out of it. Or persevere for a bit and your current chain may stretch a bit more and stop slipping
B screw adjustment, Bring the mecch up to wrap the chain around a bit more 😕
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Just a thought, nobody hit me 😯
The chain and cassette wear together. Once the chain wears it causes much more cassette wear, so you end up with both worn cassette and chain. This tends not to slip. But for some reason when you put a new chain on an old cassette, if you haven't caught it in time it'll slip.
I've known very worn chainrings to slip though regardless of chain/cassette age.
However I have not known slipping to be anything other than mis-matched chain/cassette wear; knackered chainrings; or mud or bits of grass or twigs stuck in the gaps in the cassette. If your shifting is out you can usually tell, it clicks and grinds rather than just going pong and slipping.
If one of your freehub bearings is gubbed, then it can cause gears to jump, yes. IME it's the middle of the block gears that jump, as the lack of support from the freehub bearing causes the cassette to oscillate from side to side, whereas if in a larger or smaller cog, the pressure from chain to cog stops it wobbling.
I had this very issue for the first time at Puffer 2014 on a hope pro2 hub, and then on same hub again some time later, opened it up and yes, bearing collapsed.
BUT, as I said, it was middle gears, not the 3 smallest cogs as you are experiencing.
Chainline could be a factor too, if there is wear on cassette and chain as Molgrips suggests.
Cheers everyone. Going to go for new cassette and chain and hope this solves the issues,
Thanks for reassurance it's probably not the freehub
Just to counteract what others have said, I had pretty much the same symptoms as you on my gravel bike. I knew the drivetrain was fine so I opened up the freehub and behold it was full of rusty ming. The pawls/springs were basically not engaging properly so the hub would slip uner higher torque (but be mostly fine in low torque). Didn't take long to sort it, although I am a bit worried about the seal in my hubs.
High torque at the freehub is the larger (eg 30-40+ teeth) sprockets isn’t it? (High loading at the chain/teeth interface is small sprockets though I’d agree so maybe I’m splitting hairs.)
I would check the B screw as lack of chain wrap would be exactly what is described.
How old is the chainring? And is it traditional or narrow-wide?
I had a similar problem on my old road bike, changed the freehub before eventually realising it was the Ultegra big ring. Didn't even look that bad to the eye.