Chain rubbing on rear mech cage (I think)

[Tom_One]

So... I recently replaced my chain, chainset, jockey wheels and cassette. As far as I know everything's compatible for 8 speeds, which was what I had before. The rear mech is a Shimano Deore m510 which has always worked fine.

For some reason with the new setup I get a kind of rubbing, bumping feeling in the chain when I pedal in the smallest 3 or 4 cogs on the back. It doesn't matter if I'm in the middle or biggest on the front. After ages looking at it, cleaning, reassembling and so on, the only thing I can see is that the lower jockey wheel looks like it could be slightly wonky (but it's hard to tell) and that the chain might be slightly rubbing on the rear mech as it goes onto that jockey wheel. I think the indexing is Ok, I've spent ages fiddling with that.

Has anyone else come across this? I can't see anything online. When I was fitting the new bits I forgot to adjust the limit screw and the chain came off and jammed in the back wheel  Maybe this bent the mech?

[phil d]

Your description of the lower jockey wheel as "slightly wonky" makes me wonder if you've got the jockey wheels mixed up?  The implication in your comment that you had to spend ages with the indexing to get it right adds weight to this possibility.  Not sure if that would produce the effect you are getting.  The jockey wheel with float should be at the top, nearest the cassette.

[frankly frankie]

Silly question but are you sure the chain is routed correctly, ie round the top jockey wheel and not round the useless stub of metal adjacent to it?  Hard to believe I know but I've met several cyclists in my time, happily grinding along in this mode - and it is very easily done ...

[Polar Bear]

Although you have an 8 speed setup the rear mech is effectively a 9 speed with a slightly narrower cage.   This combination is well proven and works well.

However, because the cage is narrover, my hunch therefore is that the chain previously fitted was in fact a 9 speed version.   The internal dimensions of 8 and 9 speed chains is identical so it would work just fine.

Only a hunch mind.

[Tom_One]

The jockey wheels are OK, they've got upper and lower written on (TACX ones), so hopefully idiot proof even by my standards  I did thread the chain the wrong way through the mech the first time and spent a while wondering about the noise when I was spinning the pedals in my workstand, but I've got it through the proper way now. The 9 speed chain could be the answer then. I've bought another second hand mech from someone, so going to try that first. Otherwise maybe I'll look at a new chain. Thanks for the ideas anyway 

[mattc]

I have to say that I've been fine with 8sp chains thru 9sp derailleurs. BUT
when I tried a 9sp chain on 8sp cassette, it wasn't at all happy.

Perhaps it's one of these tolerance things? I think I had a shimano cassette (HG50 probably) and a low end SRAM chain.

It's not a stiff link, is it? (In which case you'd expect it every few pedal turns, not constantly).

[Feanor]

Sure it's not still an indexing issue?

Slightly incorrect indexing setup ( cable tension ) can cause the chain to catch on the adjacent sprocket.
Not enough to cause it to shift, but enough to cause it to rattle.

Look carefully at the chain as it sits on the problem sprocket.
Does it go vertically down to the jockey wheel, with equal gaps on either side from the adjacent sprockets?
Watch these gaps as you turn the pedals.
You'll see if the chain is catching the adjacent sprocket.
Adjust cable tension in quarter-turns till it's sitting exactly right.

[bloomers100]

Maybe your gear hanger has become out of line. There is a tool you can screw into the hole that connects the rear mech that gets spun around the curcumference of the wheel, it should be touching evenely all the way around.

Worth a try.

[Oscar's dad]

Maybe your gear hanger has become out of line. There is a tool you can screw into the hole that connects the rear mech that gets spun around the curcumference of the wheel, it should be touching evenely all the way around.

Worth a try.

Do you have a link to said tool?

[bloomers100]

http://www.parktool.com/blog/repair-help/rear-derailleur-hanger-alignment

[Oscar's dad]

http://www.parktool.com/blog/repair-help/rear-derailleur-hanger-alignment

Thanks.  Useful but a bit pricey.  Do you have one?

[bloomers100]

Where's your tool?

No I don't have one.

[Oscar's dad]

Where's your tool?

No I don't have one.

Shame, I was going to ask if I could borrow it.

[Biggsy]

I got extra noise when I tried Tacx jockey wheels.  The teeth didn't fit my chain as well as Campag ones.

[bloomers100]

Where's your tool?

No I don't have one.

Shame, I was going to ask if I could borrow it.

[Oscar's dad]

 

All this is really helping the poor chap with a rubbing chain 

[bloomers100]

Sorry, but I'll bet its the cure. You started it hijacking his thread 

[Oscar's dad]

 

[Si_Co]

Is the mech moving freely? I get a similar sort of thing when the mech is full of crap, caused by the chain being 'baggy' and the mech not rotating back enough to take up all the slack when on the smallest sprockets, it's intermittent usually and is caused by tiny bits of crap, the old magic spray helps in the short term but eventually I gave take the mech apart.

[rafletcher]

Sure it's not still an indexing issue?

Slightly incorrect indexing setup ( cable tension ) can cause the chain to catch on the adjacent sprocket.
Not enough to cause it to shift, but enough to cause it to rattle.

Look carefully at the chain as it sits on the problem sprocket.
Does it go vertically down to the jockey wheel, with equal gaps on either side from the adjacent sprockets?
Watch these gaps as you turn the pedals.
You'll see if the chain is catching the adjacent sprocket.
Adjust cable tension in quarter-turns till it's sitting exactly right.

Indexing being out was my first thought, with the chain "riding" on the cocg slightly.

[frankly frankie]

Eighth-turns.  A quarter turn is easily enough to overcompensate an indexing problem.

[rafletcher]

Having completely rebuit the mech I'd be inclined to set the indexing up from scratch.

[Paul]

For some reason with the new setup I get a kind of rubbing, bumping feeling in the chain when I pedal in the smallest 3 or 4 cogs on the back. It doesn't matter if I'm in the middle or biggest on the front. After ages looking at it, cleaning, reassembling and so on, the only thing I can see is that the lower jockey wheel looks like it could be slightly wonky (but it's hard to tell) and that the chain might be slightly rubbing on the rear mech as it goes onto that jockey wheel. I think the indexing is Ok, I've spent ages fiddling with that.

Has anyone else come across this? I can't see anything online. When I was fitting the new bits I forgot to adjust the limit screw and the chain came off and jammed in the back wheel  Maybe this bent the mech?

I had exactly this problem on a new-to-me bike. Turned out the rear mech was bent. The plates that hold the jockeys were bent, so that the feed wasn't right. The evidence (apart from the obvious, when I realised what was wrong) was chain rub on the inside of the plates.

These things are generally made of very pliable alloy, so the fix was easy.

Not sure this is your problem, but worth checking before you spend more money.

[Tom_One]

For some reason with the new setup I get a kind of rubbing, bumping feeling in the chain when I pedal in the smallest 3 or 4 cogs on the back. It doesn't matter if I'm in the middle or biggest on the front. After ages looking at it, cleaning, reassembling and so on, the only thing I can see is that the lower jockey wheel looks like it could be slightly wonky (but it's hard to tell) and that the chain might be slightly rubbing on the rear mech as it goes onto that jockey wheel. I think the indexing is Ok, I've spent ages fiddling with that.

Has anyone else come across this? I can't see anything online. When I was fitting the new bits I forgot to adjust the limit screw and the chain came off and jammed in the back wheel  Maybe this bent the mech?

I had exactly this problem on a new-to-me bike. Turned out the rear mech was bent. The plates that hold the jockeys were bent, so that the feed wasn't right. The evidence (apart from the obvious, when I realised what was wrong) was chain rub on the inside of the plates.

These things are generally made of very pliable alloy, so the fix was easy.

Not sure this is your problem, but worth checking before you spend more money.

I think this could well be it. It looks like there's a bit of rub on the plates where the chain goes onto the jockey wheel, which I couldn't see at first as the oil and dirt covered it (The plates are painted black). I thought this might just be from the chain bouncing about on bumps and stuff before. Maybe it's been bent for ages but the new chain is rubbing where the old one wasn't because it's a different size, like Polar Bear said.

When you said the fix was easy, did you bend it back with pliers or a vice or something like that? I was a bit scared to start fiddling round in case I wrecked it.

[Perky]

A Wippermann with an upside down Connex link perhaps?