Shimano LX rapidfire pod problem

[Jonathan M]

My MTB has recently come out of retirement and is seeing some good use again. The components in question are Shimano LX pods, which date from around 2004. It is the rear shifter that seems to be problematic, and it is running with an XT rear mech of a similar age. The mech is a standard pull one, not one of the reverse pull versions, and I'm running with goretex cables, there does not seem to be any gear cable stiction as when it does shift it shifts well. The bike has been pretty much unused since about late 2005, and when I did stop using it regularly I can't recall a shifting problem.

The symptom is this: When on the larger cogs of the casette the thumb lever (to shift from small to big cogs) can take up to three sweeps before I get one gear shift.
On the smaller cogs shifting is fine, the usual of one thumb sweep giving up to 3 cogs on the back.
It means it is sometimes easier to make a chainring change rather than try and shift on the rear, meaning at times it is like riding a 3 speed bike.

My riding mate thought it was a slack gear cable, but this isn't the case - besides, if a gear cable is slack then you have to take up the slack before the mech shifts on the smaller cogs, and the larger cog shifting is usually fine. I've got to admit that it almost does seem like a cable tension problem, but it just happens at the wrong end of the cassette for it to be a cable tension problem.

My thought is something internal, so I've generously sprayed some GT85 through the shifter cable port, got some dirt out in this manner and on the driveway it seemed to be slightly better.

I'm assuming that this means a new shifter pod if a more thorough strip of gear cable & flush with GT85 & lube doesn't solve the problem, but has anyone else out there got any suggestions?

 

[Steve Austin]

It'll be one of two things, stiction in the cable, or a lack of movement/engagement in the shifter.
the cable is easy to fix. replace the cable, or you could try removing the inner and wiping it clean with white spirit. wipe with a oily cloth and then replace. but it will probably need replacing if it is sticking. Are you sure the filaments in the cable outer haven't been drawn into the shifter?
If its the shifter, a good squirt of something, i use wd40, will normally fix it. if its not working after a squirt of something, then it normally needs replacing. You can attempt to service it, BUT it will end in tears ime as the springs and gubbins normally ping to all parts of the known universe never to be united and work together again.

 

[Jonathan M]

It'll be one of two things, stiction in the cable, or a lack of movement/engagement in the shifter.
the cable is easy to fix. replace the cable, or you could try removing the inner and wiping it clean with white spirit. wipe with a oily cloth and then replace. but it will probably need replacing if it is sticking. Are you sure the filaments in the cable outer haven't been drawn into the shifter?

Not sure about this being a cause, the problem occurs when shifting from small to large cogs on a conventional type rear mech, so the gear shifter itself is pushing against the spring - I'd go with cable stiction if I was trying to change from large to small, when cable stiction will slow down how quick the spring can "pull" the mech down the cassette. Also the cable is a gore tex cable, and while these are not 100% and do wear out, the bike wasn't used enough prior to being rested for the relatively new cables to cause a problem, I'd expect more time from the cable yet, but as part of the problem solving will strip the cable out anyway and see whats what.

If its the shifter, a good squirt of something, i use wd40, will normally fix it. if its not working after a squirt of something, then it normally needs replacing. You can attempt to service it, BUT it will end in tears ime as the springs and gubbins normally ping to all parts of the known universe never to be united and work together again.

I think it "feels" like a shifter problem, especially from the erratic nature of the problem only occuring on the larger cogs, almost as though the increased cable tension at this point is contributing. Your advice to replace if lube does not work confirms my previous experiences that rapidfires are not user serviceable, but the pods are also not the most expensive parts to replace fortuntaely.

EDIT: Been out in the cold today, and repeated the GT85 process. I've then used a slightly heavier "dry" spray lube via the cable port, and on the workstand and driveway the problem seems to be solved. Makes me think that lack of use had maybe allowed some part of the ratchet mechanism to become sticky, which the GT85 has freed up. The final test is of course to get it out in the mud and see if what works on the driveway works in the wild!