Replaced Chain - Help - skipping/jump on chainset cycle

[shaunpalmer]

Replaced the chain on my 1998 Marin Rift Zone which as a LX derailleur, HG cassette, STX-RC chainset and front derailleur. I replaced with a HG chain using the same number of links as the old chain. The old chain was an IG.

When I apply power in rear gears 6/7/8, the chain seems to skip/jump with a clunk. This seems to happen on a cycle of the chainset.

I have ordered an IG chain thinking maybe that is the issue, but could it be something else?

could it be a bent bottom bracket axle, or the chainset/rings, cassette, derailleur ?

 

[We_are_Stevo]

You don't say which ring you are on at the front when it happens? You didn't ought to be on the big ring at the front if you are using the lower three at the back...

Otherwise it could just be a simple matter of correct adjustment - turn the bike upside down (I don't subcribe to the school of thought that says you shouldn't!) and move the derailleur across the block whilst on the middle ring - does the upper jockey wheel line up with the sprockets correctly? Does the derailleur reach the biggest sprocket alright? Is the shift precise?

The main reason for shifting errors on a new build is cable stretch - take up the adjustment, or retension the cable.

Correct chain length is judged by running the chain round the biggest ring front and rear without the rear derailleur, seeing where it meets and adding two links (1 1/2 if using a 'quick-link' connector) so worth checking...

None of this is rocket-science, it's just down to trial and error (and confidence...), and making small adjustments and testing each time. Once you get the hang of it you'll wonder why you even asked...

 

[Andy B]

You say you replaced the chain...

...did you replace any of the other drivetrain parts? (chainrings/cassette/jockey wheels)

How old are the chainrings, cassette and jockey wheels?

A new chain on worn rings/cassette is known to cause similar skipping symptoms to what you describe in your opening post

Could also be a stiff link in the new chain, usually where it was joined. But check all the links rotate freely.

 

[shaunpalmer]

It happens in the middle and inner ring (higher gearing) on the front.

The linkpin doesn't seem to be stiff.

The rear mech alignment seems to be ok, shifts ok, unless trying to go up through 6,7,8 under acceleration.

I haven't replaced anything else (yet) - just the chain. Its all original, except chainset was replaced a couple of years ago as I cross threaded inserting the pedals

 

[jimo746]

I had similar symptoms when I replaced the chain on my 1997 Proflex a while ago, I found that the problem was cured when I also replaced the cassette.
Although the cassette didn't look particularly worn (it may have been the original cassette) on closer inspection the teeth were worn more on one side than the other and the new chain did not sit quite right on the teeth of the cassette.
Try adjusting first, checking for stiff links etc, if no joy then cassettes can be had fairly cheaply from places like Chainreaction cycles etc.

 

[captaincosmic]

skip

I am afraid its just one of those things the longer you use a worn chain the more damage it does to the cassette etc
Its not uncommon to have to replace cassette and chain at the same time
as they tend to wear each other out :cry:

 

[the_duke]

It may also be worth checking you have used the right speed chain.

If its too narrow (intended for 8-9-10 speed) it may not engage the teeth properly if you are running 7 speed for example.

But I agree, when fitting a new chain a new cassette is often needed.

 

[gump]

Re: skip

I am afraid its just one of those things the longer you use a worn chain the more damage it does to the cassette etc
Its not uncommon to have to replace cassette and chain at the same time
as they tend to wear each other out :cry:

Yep, I always do both at once

 

[shaunpalmer]

Thanks Guys. New HG70 Cassette has been ordered (Merlin via ebay had the best price) ... watch this space

 

[Anthony]

Re: skip

I am afraid its just one of those things the longer you use a worn chain the more damage it does to the cassette etc
Its not uncommon to have to replace cassette and chain at the same time
as they tend to wear each other out :cry:

A cassette should last longer than a chain, but it depends how careful you are with your chains. If you wait until gears skip, then it is quite likely that the cassette will be worn out as well as the chain. If you replace the chain as soon as 24 links measure more than 12 1/16th", a cassette should last for several chains. Usual advice is to replace at 12 1/8th", then maybe the cassette will last about two chains.

Replacing chains is the most important, because a worn chain will wear out a cassette more than a worn cassette will wear out a chain.