Chain jumping

Mikehatton

Hi All, 1st post... be gentle!

I'm having trouble with the chain jumping in the highest gear. I 1st came across the problem after I bound a load of grass around the cassette but the problem persisted after I cleaned it off. I've changed the rear cassette and chain and it worked okay for a few hours riding but it's a problem again now even though I've been very careful to keep things clean(ish). I've taken a link out the chain and adjusted the rear mech so it wraps tighter and it is a little better but still very annoying when it jumps.

Is it possible I could've damaged the chain so soon? My route has a lot of short and very steep sections as well as some steps to climb, the bike is quite heavy and I'm not a featherweight.

Thanks,

Mike.

cooldad

Could be many things.
How did you size the new chain?
How did you join the chain?
Does the chain have a stiff link after joining?
Is the mech indexed correctly after changing the cassette?
Are the chainrings worn?
Is the mech bent?

And probably a few more I haven't thought of.

Mikehatton

I've checked the links and they all feel free, there's nothing missing and no additional play in any of the links.
The local bike shop specified and sold the chain and cassette to match, they're a bunch on enthusiasts and have a busy workshop full of high end bikes so I had no reason to doubt them. They've taken a look and advised removing the link from the chain.
The chain rings were new and haven't seen much use, there's no obvious damage there either.
By 'indexing' you mean adjusting the cable and stops to suit? Done that and done it again to be sure, everything is working fine other than that one cog. The mech moves and sits happy, by eye it looks spot on.

cooldad

The chain needs to be sized on the bike, no other way.

Or mech hanger could be bent.

But if none of the above, I'm out of ideas. But if it's the smallest cog I would still susepct a vstiff link, or bad join.

dirkpitt74

What bike is it?
Is it a Hard Tail or Full Suspension?
As CD said - how did you size the chain?

Mikehatton

It's an '08 Mongoose Otero Elite, soft tail.
When we're talking about sizing the chain, is that the length in terms of number of links or the actual link size? We've reduced the number of links to tighten it up on the cogs.

dirkpitt74

Overall chain length.

Is your rear wheel on square? Just thinking if its not quite lined up it could may be throw the chain.

cooldad

Mikehatton wrote:

It's an '08 Mongoose Otero Elite, soft tail.
When we're talking about sizing the chain, is that the length in terms of number of links or the actual link size? We've reduced the number of links to tighten it up on the cogs.

That's not the same as measuring the chain. Try around big/big, excluding the mech, plus one or two full links depending on chain growth at whatever point the maximum extension is along the travel.
Workshop full of high end bikes or not, advice to remove a link without actually measuring the chain is not good advice. Sounds like they were maybe just getting rid of you as you didn't have them fit the parts.
And if everything else is set up correctly, one extra link wouldn't be causing the problem. Obviously as the problem is still there.

Mikehatton

Overall chain length has been shortened to tighten it up a bit and certainly won't go any shorter. Checked the rear wheel but I'll double and triple check on all the suggestions made. You guys don't think it's possible the chain has pulled or stretched then? If I can't find anything wrong I may just have to adjust the rear mech so it won't change into top gear.

dirkpitt74

Have look at this Park Tool Guide for chain length sizing.

Mikehatton

Thanks for that. There's only a little bit of chain spare big-big, small to small the mech still keeps it from sagging. There's something still not quite right so I'll look over again tonight and let you know if I find anything.

cooldad

By top gear assume you mean the small cog. Sometimes people are a bit vague.

Mikehatton

yeah, the little one. Sorry, I've always worked on my own bikes but don't have a clue on the names of the parts... learning as I go.