Why the chuff is my chain slipping?

[KneesUp]

My chain is skipping, and I can’t work out why. I don't mean it's trying to change gear, it just seems to skip over the teeth on the rear but stay in the same gear. I thought at first it was a stiff link, because I've not been that vigilant with the maintenance over winter, and it was a little old, so I swapped the chain, and it still did the same thing. So then I decided it must definitely be the freehub, so I swapped the wheel, and it is still exactly the same. Whenever you put more than a little pressure through the pedals (i.e. whenever you go uphill or start from the lights) it clicks over a tooth or two on the back - it's not a trimming issue because I have the same friction shifters I've had for years and no matter how I fiddle I can't stop it.

I was so convinced it was the freehub I went to buy a new wheel the other day but I couldn't find one that fit my needs, so I put a spare (was awaiting a new spoke, but it's still straight) and was most annoyed that the problem is exactly the same. Each wheel has a cassette on and I didn't bother changing them, so it's doing the same thing regardless of cassette. I don't think it's chain length because it's the same as the previous one. I don't think it's a stiff link because I've changed the chain. I don't think it's a cable tension issue because I can trim as much as I like and it still does it. I don't think it's a hanger issue as the bike hasn't been hit by anything to my knowledge.

Any suggestions as to how to stop it very much appreciated!

 

[si_c]

Have you checked your chainrings?

 

[KneesUp]

Have you checked your chainrings?

Pretty sure it's the back that's the issue - I have a triple up front and it does it whether I'm on the middle ring (fairly new 38t from Spa) or outer ring (old but fairly unworn 48t Shimano) I've not tested it with the inner ring to be honest, but the symptoms are identical using either of the other two.

 

[Ajax Bay]

it [the chain] was a little old, so I swapped the chain, and it still did the same thing.
. . . .
I put [on] a spare [wheel] . . . and was most annoyed that the problem is exactly the same. Each wheel has a cassette on and I didn't bother changing them, so it's doing the same thing regardless of cassette.

Assuming you replaced the chain with a new one, my suggestion is this:
Chain had elongated too far, the cassette had worn in synch, and when the OP put the new chain on, unsurprisingly it slipped. Then the OP swapped the wheel for another (with its own cassette). New chain slipped on it - because that cassette was worn (eg had done more than 2000 miles).
Solution: buy new cassette, fit (assume to original wheel) and ride without chain slipping. Consider buying another cassette for the spare wheel and replace both spoke and cassette.

 

[alicat]

^^^^

 

[KneesUp]

Assuming you replaced the chain with a new one, my suggestion is this:
Chain had elongated too far, the cassette had worn in synch, and when the OP put the new chain on, unsurprisingly it slipped. Then the OP swapped the wheel for another (with its own cassette). New chain slipped on it - because that cassette was worn (eg had done more than 2000 miles).
Solution: buy new cassette, fit (assume to original wheel) and ride without chain slipping. Consider buying another cassette for the spare wheel and replace both spoke and cassette.

I understand what you are saying, but it doesn't feel like that can explain it - the symptoms are identical with both cassettes (and both had previously been fine very recently - one set of wheels is slick, the other knobbly - I generally have the slick ones on but swapped to the knobblies when it snowed. I snapped a spoke on the 'slick' rear when cleaning it (don't ask, but also, don't lean on a spoke when you are reaching for a cloth) so I put the slick onto the 'knobbly' wheel. Then it started skipping, so thinking that riding in the snow had possibly buggered the freehub on the old and never-very-good hub in the week or so it had sat since I last rode it, I put the slick back on the original wheel (minus 1 spoke) and that too skips - in exactlly the same way. Both wheels do it in various gears too. I should add that they're only 8 speed, not your modern 10 speed plus, so they're fairly sturdy. And I only had the 'knobbly' wheel on for a fortnight of commuting (so a total of no more than 60 mile) which seems a very short time for it to wear to a given chain (the wheels were previously on another bike with another chain).

That said, Mrs Knees very rarely rides her bike, so her cassette is effectively brand new so I'll borrow that and see what changes.

 

[fossyant]

Try a new cassette. I'd say they are all worn and won't mesh with the new chain.

 

[Ajax Bay]

the symptoms are identical with both cassettes (and both had previously been fine very recently . . . Then it started skipping, so . . . I put the slick back on the original wheel (minus 1 spoke) and that too skips - in exactlly the same way. Both wheels do it in various gears too. I should add that they're only 8 speed, . . . I only had the 'knobbly' wheel on for a fortnight of commuting (so a total of no more than 60 mile) which seems a very short time for it to wear to a given chain (the wheels were previously on another bike with another chain). That said, Mrs Knees very rarely rides her bike, so her cassette is effectively brand new so I'll borrow that and see what changes.

Both cassettes were fine with the old chain: because they were worn to it. But eventually the chain elongated beyond the point that the cassette could cope with. And then with a new chain, both slipped. Nothing you've added affects or undermines my suggestion. Borrowing an 'effectively brand new' cassette is an excellent test opportunity. Good luck (but you won't need it).

 

[Racing roadkill]

Worn chainrings or bunching of the chain through the tensioner / Jockey wheels, due to wear, or built up grot, would be my guess.

 

[User6179]

I understand what you are saying, but it doesn't feel like that can explain it - the symptoms are identical with both cassettes (and both had previously been fine very recently - one set of wheels is slick, the other knobbly - I generally have the slick ones on but swapped to the knobblies when it snowed. I snapped a spoke on the 'slick' rear when cleaning it (don't ask, but also, don't lean on a spoke when you are reaching for a cloth) so I put the slick onto the 'knobbly' wheel. Then it started skipping, so thinking that riding in the snow had possibly buggered the freehub on the old and never-very-good hub in the week or so it had sat since I last rode it, I put the slick back on the original wheel (minus 1 spoke) and that too skips - in exactlly the same way. Both wheels do it in various gears too. I should add that they're only 8 speed, not your modern 10 speed plus, so they're fairly sturdy. And I only had the 'knobbly' wheel on for a fortnight of commuting (so a total of no more than 60 mile) which seems a very short time for it to wear to a given chain (the wheels were previously on another bike with another chain).

That said, Mrs Knees very rarely rides her bike, so her cassette is effectively brand new so I'll borrow that and see what changes.

I had a similar symptoms, usually pulling away from junctions, it turned out to be the top jockey wheel which had worn down and the bolt that goes through it had corroded stopping the jockey wheel from moving from side to side
I had changed the wheel, cassette, chain and gear cable before I figured out it was the jockey wheel

 

[KneesUp]

I had a similar symptoms, usually pulling away from junctions, it turned out to be the top jockey wheel which had worn down and the bolt that goes through it had corroded stopping the jockey wheel from moving from side to side
I had changed the wheel, cassette, chain and gear cable before I figured out it was the jockey wheel

Perhaps I should have mentioned that the rear derailleur is almost 30 years old ... (in good condition though - I suspect that it wasn't used for at least 25 of those years)

 

[KneesUp]

Thanks all. On watching it happen from the side of the bike rather than trying to look when riding, it was clear that the rear derailleur has stiffened up (still blaming the snow, and grit) so it doesn't move properly anymore meaning the gap between the top jockey wheel and the cassette was huge. I've fitted a spare out of the parts pile, and now just need to take the tyre and tube off the 'missing spoke' wheel onto the other wheel.

 

[Bianchi boy]

sounds to me that you may have put the chain on back to front -- Make sure the writing on the chain links, is facing out from the bike, Worth checking, as this happened to me

 

[Crankarm]

Perhaps I should have mentioned that the rear derailleur is almost 30 years old ... (in good condition though - I suspect that it wasn't used for at least 25 of those years)

Perhaps it's time you invested in a new derailleur for your antique bike and renew everything else at the same time?

 

[Illaveago]

Does it only happen in one gear or in different positions ? As you have changed the wheels and it still occurs then I would have thought that it points to the a fault with the rear derailleur ? Is the tension on the arm sufficient to take up the slack of the chain or is it loose and allowing the chain to jump ?