Gear indexing woes

[JoeyB]

Trying to help a lad at work with gear indexing. We have fitted a new chain and the gears aren't shifting correctly.

I can get them going up reasonably well, but coming down, the chain seems to lift up and ride the edge of the cassette teeth rather than actually drop to the lower cog.

Could this be down to the rear cassette being knackered or is it more likely dirty cables?

 

[DWiggy]

I've got a similar problem and I think its down to a worn rear derailleur that has a bit too much play, I previously fixed the problem by replacing the badly worn jockey wheels but this time the arm has too much side to side play, give it a wobble and see, it play havoc with indexing.

 

[JoeyB]

That would make sense, its as if the RD isn't making a positive enough movement. If you flick the RD whilst spinning the pedals it seems to nudge it onto the correct cog...Should the jockey wheels have any play in them? The one closest to the cassette certainly has some slack in it...

 

[JoeyB]

I think the other thing that doesn't help is the megarange cassette he has. Its a 9 speed 11-34t and there are some big jumps in the middle of the cassette...this is where the issue is most noticeable.

 

[MrWill]

I had the same problem on what sounds like the same set up. The rear hanger was bent.

Have you put the right speed chain on?

Jockey wheels shouldnt have much play in them.

 

[screenman]

I take it you have checked the obvious, which is rear mech hanger alignment. If not it is the very first thing that should be checked, although most people miss it out, then wonder why they struggle to get a smooth change.

 

[User269]

It's often necessary to change the cassette at the same time as the chain; even if the cassette's not too worn, it may not work well with a new chain.

 

[DWiggy]

I replaced my 105 jockey wheels over for some ceramic ones (only £20) and this initially solved my problem, they should only have a little play but mothing massive.

My mech is now showing signs it's just worn out where it's bolted to the hanger there is quite a bit of side to side play it, only takes a few mm out for it to fall out of especially in the larger cogs a this is where the rd is under the most stress from the cable

 

[rusty bearing]

Generally you would need to change the cassette/freewheel with the chain when it's more than 75% worn or it will skip when changing. However if you can get it indexed to go up but not down properly or down but not up etc then you have a sticky shifter cable. The mech pivot wear if excessive as well can add to the problem.

 

[Big_Dave]

my mtb 9 speed 11-34 cassette changes gears lightening quick, a mega range should not cause any problems unless it's worn out, had a similar problem with it once with old cables, but as others have said, a bit of wear here and there mount up and cause problems.

 

[Kbrook]

I had the same problem which was fixed yesterday, it was drivingnme nuts, I had changed my chain, cassette, checked the hanger, even changed the cable to the rear derailleur. Every time it would change up fine but not down. In the end I took it to the LBS who took five minutes to change the cable outers. Sorted straight away. He explained that when you go up the block the pressure of the lever is enough to tighten the cable, but any shoot in the outer will prevent a proper release of the spring in the RD.

I bet you have the same issue.

 

[Nigelnaturist]

^^^^^^^^
My betting is cables and don't forget where the cable goes under the BB

 

[fatboy123cycling]

My bet is worn cassette - new chain will find any wear - remember all the sprockets do not wear consistently. It can be an expensive job when you need to change chain, cassette and chain wheels.

 

[screenman]

You lot do not do mech alignment do you.

 

[Nigelnaturist]

My bet is worn cassette - new chain will find any wear - remember all the sprockets do not wear consistently. It can be an expensive job when you need to change chain, cassette and chain wheels.

I have just replaced my chainset through choice not because its worn out, and its done 10,000+ miles, cassettes well depends on level even 105 cassettes can be had for £22-23 and Ultegra 6700 for £30, I would expect 6000 miles from a cassette minimum of 3,000 from a chain, £60 a year on chains £40-60 on cassettes hardly expensive, but as I say depends on level of kit.
Look at what is happening, its changing up but not down as if something is holding it back or the spring isn't strong enough, to me thats extra friction somewhere that the return spring can not over come.