New chain and can't index rear gears!

CRAIGO5000

I've tried tuning this out now for probably three weeks and it's really annoying me!

My old chain came with the bike (KMZ 114 links) I replaced it after putting 700 miles on the bike and put on a SRAM PC850 with master link (114 links).

As soon as I swapped it out I noticed there was an issue with slight vibration in certain gears and also clean gear changing. I then attempted to tune it out via the barrel adjuster with no success. Basically I can only ever have crisp gear changes going down the gears which then affects going up the gears. If I tune the adjuster to improve shifting going up the gears, then going down the gears gets messed up and the chain simply rubs the cogs and skips as it attempts to change.

There are no stiff links in the new chain.
The H and L are set correctly.
I've lubed the dérailleur pivot points.
I've undone the rear dérailleur cable and started over from fresh to no avail.
The cable is clean and runs through the track of the bottom bracket and cable guides cleanly.
The rear cassette appears to look okay, the teeth look good.

What else could I try? I'm this close to angrily kicking the dérailleur in and putting my foot through the spokes and then if I don't feel any better, I'll be throwing the bike through the nearest window - maybe. :shock:

Thanks!

nicklouse

have you sized the chain correctly?
it does sound like a cable issue.

CRAIGO5000

What does "sizing the chain" involve? I basically counted the links on the old chain and made sure the new one had the same amount and was also 1/2" × 3/32".

I understand the old chain would have stretched slightly so that's why I made sure to count the links.

It seems too coincidental to be a cable issue. The gear change was 100% silky and immediate until I swapped the chain and now I'm left with a bike that's difficult to ride smoothly.

vinnn

Despite your cassette 'looking' OK, sounds to me like the chain stretch has worn your cassette and you may need to replace that as well. Before you invest in a new cassete though I agree with nicklouse that a new rear gear cable (both inner and outer) works wonders and is relatively cheap to replace, that should be your first port of call.
Your new unstretched chain will be less flexible laterally and therefore will be less tolerant of inaccurate gear selection caused by running an old cable.

On a side note, might sound a silly question but you did buy the right width chain for your cassette didn't you? (aka 10 speed chain for a 10 speed cassette etc.)

HTH

CRAIGO5000

vinnn wrote:

Despite your cassette 'looking' OK, sounds to me like the chain stretch has worn your cassette and you may need to replace that as well. Before you invest in a new cassete though I agree with nicklouse that a new rear gear cable works wonders and is relatively cheap to replace, that should be your first port of call.
Your new unstretched chain will be less flexible laterally and therefore will be less tolerant of inaccurate gear selection caused by running an old cable.

On a side note, might sound a silly question but you did buy the right width chain for your cassette didn't you? (aka 10 speed chain for a 10 speed cassette etc.)

HTH

That makes sense regarding lateral flex and the gear change does "sound" like it wants to change but just doesn't jump the cog until I overshoot the barrel adjuster with detrimental effects to selecting gears in the opposite direction.

The replacement chain was for an 8 speed cassette (114 links) and I have a 7 speed cassette which sounds odd BUT the chain spec is the same at 1/2" × 3/32" and the number of links from the chain I removed (which came with the bike from new) also counts 114 links. I think my bike takes an 8 speed chain simply because it has a Shimano mega-range 7 speed cassette where gear 1 is huge compared to gear 2?

Or have I made a school boy error? :oops:

Blue Meanie

Bent or twisted mech/mech hanger?
Worn busings in mech?
Have you adjusted the B-Tension?

I'd re-visit the mech:
Is it straight, not leaning in or out? Are the jockeys wheels in line, mech cage twisted? Kicking it might help if it's this

A mech that 'prefers' one direction to another sounds like incorrect cable tension, however in a worn mech you sometimes need an extra bit of tension (barrell adj out) to help it climb up the cassette, which in turn makes it slow to get back down - or set up the other way (barrell adj in) it drops easily but doesn't 'catch' on the way up.

B-Tension: In the smallest cog, set B tension so jockey wheel doesn't foul cassette, check your 1st mega-range doesn't either. Keep jockey wheel as close as possible to cassette.

vinnn

A quick Google shows me that chains intended for 7 & 8 speed cassettes are the same width and that width only becomes important on 9 speed cassettes and up so it seems you're OK there.

So personally, I recommend changing the rear gear cable (both inner cable and outers).
If you're doing it yourself do it properly and get yourself a pair of cable cutters, they make the job super easy.
Then if you've still got gear changing issues I'd consider changing the cassette, if the cassette's really worn, chain skipping under hard pedalling will occur on the most worn spockets. If you're getting any chain skipping then your cassette is definately well overdue for replacement and it'd be likely that you have the same amount of wear on the chainrings too.

CRAIGO5000

Cheers for all the help guys, I revisited the mech this morning and spent 90 mins tweeking, releasing the cable, re-torquing, lubing and also double checking for tight links. I've managed to sort it in the end and my 7 mile cycle to work was nice and pleasant again.

The slight vibration has now gone and each gear now changes nice and quickly with minimal stutter. God knows what I did to eventually sort it as I had just about adjusted everything that I could.

RE: the chain,Vinnn you're right, the only difference between 7-8 speed chains is the length. I counted 114 links on both and also checked the new chain against Sheldon Browns guide which states to wrap the chain around both large cogs but not thread it through the dérailleur and to ensure you have 2 links overlap - which I did.

All is good in the hood again