Any bike mechanic out there to sort this little problem?

steve9uk

I run a 9 x 3 mtb with a not so old rear sram cassette and sram chain. I had a Shimano xtr rear derailleur which needed to be replaced. Due to availability i had to buy a Shimano alivio to tie me over until i found a replacement.
So i started to set the the derailleur up, setting the limit screws,B screw and setting the shifting.
Went through all the shifting which on the bike stand shifted great. Took the bike out the next morning and had this problem!......
Had the chain on the Large chain ring at the front and shifting through the sprockets at the back...no problems.
Shifted to the small chain ring and went shifting through the rear sprockets... no problems
Had the chain on the middle chain ring and shifted through the sprockets and found the jockey wheel jumping/skipping??? Tried adjusting the gears which seemed fine on the stand.??
Anyway the replacement derailleur came and so i fitted it but still had the same problem?
I had an old chain that lying around (which was stretched slightly) and fitted that, now the problem has gone, even shifts perfect??? Obviously i dont want to keep the old chain on in case it snaps, i was just trying it to see what would happen. Any ideas please
This is my current set up...
Xtr mech, xtr rear derailleur, sram chain and cassette.
Is there a problem with the above up??

Thank you

reaperactual

I'm not a bike mechanic although have come across most problems with shifting.

I honestly cannot think why the skipping is only on the middle ring and fine on the outer and inner rings. Taking that out of the equation and seeing as the older slightly stretched chain works fine in all gear combinations and new one doesn't only suggests the rear cassette is worn and not meshing with the new chain which is causing the skipping.

Depending on how 'not so old' the cassette and old chain is, maybe it's long enough to have worn the cassette?

I tried to replace a chain after 8 months and new chain wouldn't mesh with the cassette so rather than buying a new cassette straight away I put the old chain back on and decided to 'run them into the ground' until shifting suffered or chain snapped.

Carried a spare missing link in case and it all ran well for another 8 or so months with no chain break or noticeable shifting problems. Only cost around £50 for new cassette, triple front crankset that I only bought because I was selling the bike to a friend. Maybe this method is worth a try given your situation?

JBA

Middle chain ring worn?

steve9uk

Thanks guys for your reply.
Just checked and the cassette and chain were both changed in Jan 2020.

Darius_Jedburgh

Not infrequently it pays to replace the whole set and cables. And that front mech needs to go.

That cassette looks worn. Stop doing things piecemeal and stop penny pinching.

ed1973

I had the same issue and it was so frustrating, I bought a new chain and it kept skipping so bought a new cassette and boom problem solved, it’s amazing how quickly a warn chain can knacker a new cassette.

steve9uk

I'll change the cassette and chain again. If its not that then i have a spare.

Thanks

steve9uk

Darius_Jedburgh said:

Not infrequently it pays to replace the whole set and cables. And that front mech needs to go.

That cassette looks worn. Stop doing things piecemeal and stop penny pinching.

Darius the front mech is shifting perfect. Not getting any problems. Just the jockey wheel skipping

JBA

The cassette and chain were both new in January so it's unlikely to be them (unless you are doing mega miles).
How worn are the jockey wheels?
Similarly, what condition is the middle chain ring in? It is usually the one that is used the most so wears more quickly than the inner or outer rings.

david37

have you threaded the chain through the derailleur properly?

steve9uk

JBA said:

The cassette and chain were both new in January so it's unlikely to be them (unless you are doing mega miles).
How worn are the jockey wheels?
Similarly, what condition is the middle chain ring in? It is usually the one that is used the most so wears more quickly than the inner or outer rings.

Hi JBA
The jockey wheels are new as it came with the new derailleur.

steve9uk

david37 said:

have you threaded the chain through the derailleur properly?

Hi David
Yes checked everything is threaded through properly.

steve9uk

JBA said:

The cassette and chain were both new in January so it's unlikely to be them (unless you are doing mega miles).
How worn are the jockey wheels?
Similarly, what condition is the middle chain ring in? It is usually the one that is used the most so wears more quickly than the inner or outer rings.

i could try changing the middle chain ring. Just seems strange that the jockey wheels dont skip when i put an old chain back on? im stumped

First.Aspect

Which jockey wheel is skipping?

If its the upper one, its not a chain line issue it is a B-limit or cassette issue. Have you tried extreme B-limit settings to see if you can induce the problem on the big or small rings?

Whatever the problem is, I don't see how it can be the state of the chain ring.

First.Aspect

steve9uk said:

JBA said:

The cassette and chain were both new in January so it's unlikely to be them (unless you are doing mega miles).
How worn are the jockey wheels?
Similarly, what condition is the middle chain ring in? It is usually the one that is used the most so wears more quickly than the inner or outer rings.

i could try changing the middle chain ring. Just seems strange that the jockey wheels dont skip when i put an old chain back on? im stumped

Hadn't spotted this.

It is the cassette. A new chain will sit higher on the teeth of a worn cassette than an old chain.

steve9uk

First.Aspect said:

steve9uk said:

JBA said:

The cassette and chain were both new in January so it's unlikely to be them (unless you are doing mega miles).
How worn are the jockey wheels?
Similarly, what condition is the middle chain ring in? It is usually the one that is used the most so wears more quickly than the inner or outer rings.

i could try changing the middle chain ring. Just seems strange that the jockey wheels dont skip when i put an old chain back on? im stumped

Hadn't spotted this.

It is the cassette. A new chain will sit higher on the teeth of a worn cassette than an old chain.

Hi First. its the lower jockey wheel that skips. but i placed the old chain back on and the skipping stopped? could it be a faulty new chain??

steve9uk

ill try changing the cassette and chain. at worst if it does not work i have a spare set.
Thanks all for your input.
ill keep yous posted

steve9uk

steve9uk said:

JBA said:

The cassette and chain were both new in January so it's unlikely to be them (unless you are doing mega miles).
How worn are the jockey wheels?
Similarly, what condition is the middle chain ring in? It is usually the one that is used the most so wears more quickly than the inner or outer rings.

i could try changing the middle chain ring. Just seems strange that the jockey wheels dont skip when i put an old chain back on? im stumped

done very little miles as i broke my finger and was off the bike for 8 weeks

thecycleclinic

This problem with jumping lower jockey wheels mean the chain is jumping as it leaves the chainring and feeds into the jockey wheel. Regardless of when the ring was changed, change it. It could resolve your problem. I have had exactly this issue before with campagnolo chorus. Ring did not look worn but it was in such a way to cause exactly this sort of problem. Seem the issue since. 90% certain this is the main issue.

First.Aspect

steve9uk said:

First.Aspect said:

steve9uk said:

JBA said:

The cassette and chain were both new in January so it's unlikely to be them (unless you are doing mega miles).
How worn are the jockey wheels?
Similarly, what condition is the middle chain ring in? It is usually the one that is used the most so wears more quickly than the inner or outer rings.

i could try changing the middle chain ring. Just seems strange that the jockey wheels dont skip when i put an old chain back on? im stumped

Hadn't spotted this.

It is the cassette. A new chain will sit higher on the teeth of a worn cassette than an old chain.

Hi First. its the lower jockey wheel that skips. but i placed the old chain back on and the skipping stopped? could it be a faulty new chain??

Sorry, stumped then. Only time I've had that is worn jockey wheel. Seems unlikely to me to be the chainring itself, given the length of untensioned chain between them, and how much vertical motion you get in that part of the chain when riding. If it were that sensitive, this would happen routinely. But happy to be proved wrong.

Possibly still the problem I had posited though - chain run through the cage might be off from the start and only fully coming off the lower jockey wheel.

steve9uk

thecycleclinic said:

This problem with jumping lower jockey wheels mean the chain is jumping as it leaves the chainring and feeds into the jockey wheel. Regardless of when the ring was changed, change it. It could resolve your problem. I have had exactly this issue before with campagnolo chorus. Ring did not look worn but it was in such a way to cause exactly this sort of problem. Seem the issue since. 90% certain this is the main issue.

Thanks for the advice, ill do that

steve9uk

First.Aspect said:

steve9uk said:

First.Aspect said:

steve9uk said:

JBA said:

The cassette and chain were both new in January so it's unlikely to be them (unless you are doing mega miles).
How worn are the jockey wheels?
Similarly, what condition is the middle chain ring in? It is usually the one that is used the most so wears more quickly than the inner or outer rings.

i could try changing the middle chain ring. Just seems strange that the jockey wheels dont skip when i put an old chain back on? im stumped

Hadn't spotted this.

It is the cassette. A new chain will sit higher on the teeth of a worn cassette than an old chain.

Hi First. its the lower jockey wheel that skips. but i placed the old chain back on and the skipping stopped? could it be a faulty new chain??

Sorry, stumped then. Only time I've had that is worn jockey wheel. Seems unlikely to me to be the chainring itself, given the length of untensioned chain between them, and how much vertical motion you get in that part of the chain when riding. If it were that sensitive, this would happen routinely. But happy to be proved wrong.

Possibly still the problem I had posited though - chain run through the cage might be off from the start and only fully coming off the lower jockey wheel.

Thanks First i'll double check everything

steve9uk

Hi all. Just an update. I replaced all the chainrings and the problem with the skipping jockey wheel has gone. I would have never thought it would have been that. Although I’ve had to put the small chainring back on as a temporary measure as the new one was flat. So apparently I need to measure and buy something spacers. Thanks for your help. Appreciated