Gear's jumping on rear wheel: what do I do next ?

Brocade

Folks,

I had posted about this a month back: I have a Shimano Deore LX groupset on a Specialized Tricross 2008 Sport and the gears are somewhat unstable in the rear wheel, occasionally jumping up and down all over the place.

Earlier advice was that I reindex the gearing, which I did. It marginally helped but the problem has not really gone away. I would say it is 30% better, so mostly still there. I hesitate to get up out of the saddle and really step on it.

What should I do ? What would people recommend I focus on next:
1. new chain ?
2. new cassette ?
3. change cables ?
4. change rear derailleur (getting ugly)
5. change the entire groupset (ouch) ?

The bike is not terribly old, it's got about 1000 miles on it.

Thanks in advance,
Tolga

pastasauce

Ok, this is the most unlikely cause for slipping gears, but my commuter had been slipping and getting progressively worse over 2-3 weeks and i couldn't find any fault.

It culminated yesterday with it being virtually unrideable so I checked and double checked everything before I found the cause.

Chainset side chainstay split in two behind the chainset !

Bike is only 13 months old and luckily with a lifetime guarantee !

amaferanga

Probably cables next.

You definitely shouldn't need a new drivetrain after 1000 miles. Chain and cassette should be fine. Rear mech should be fine unless its taken a knock.

I wonder if your rear mech hanger might be bent? It apparently takes quite a knock to the mech to bend the hanger, but even a very slight bend can mess with the indexing of the gears (I know this from experience).

Brocade

OK let me check the rear mech hanger and see what;s happening there. If that is not it, cables next I guess.

Many thanks for the advice,
Tolga

Mister W

It shouldn't be a cable, unless it's sticking somewhere. Adjusting the indexing would sort out any issues with stretched cables.

My vote is a chain problem. Check if you've got any damage to the chain.

John.T

Clean and grease the cables. Then re-index.
Also check the chain for a sticking or damaged link.

muchalls

I had a subtly bent rear hanger: it caused poor indexing in that you could get either the lower range gears ok but reluctant/auto shifting on the higher ones, or vice versa.
the best way to check this however is with a special tool: it bolts onto the hanger and checks alignement against the wheel rim. Luckily a mate of mine has one so I got it sorted.

desweller

+1 for cables. Be careful to check within the shifter itself - as it's the trickiest place to examine, it's often the place people don't bother to look.

Also +1 for chain though - I bought a new bike at the beginning of the year, and the chain was responsible for disengaging from the big chainring under load (despite measuring a precise 1/2" pitch). Never did work out what was wrong with it, but fitting a new chain sorted it out.