Rear mech playing up - what to look at?

[minimoog]

Hi - a tentative first post in this borough of PH...

In the last week or two my rear gearshift has started working only when it feels like it. I'm ashamed to say the bike has spent rather too long of its 10 years in the garage and very little time on the road (probably only a few hundred miles on it in total... ), so shouldn't be worn out as such, but it's definitely playing up.

It's a Deore LX mech with rapidfire shifter, of around 10 years vintage as I say. I've cleaned and lubed the derailleur itself and can't see anything amiss with the cable run, but at a guess perhaps it's stretched or sticking due to old lube or crud in the sleeves. Or something.

I'm not really sure how to go about diagnosing this as I've never needed to work on the bike before. Can anyone give me some ideas? Obviously in extremis I can drop if off at my local repairer but I don't mind having a crack myself if I can get some guidance.

Any tips gratefully received

[Mars]

If the cable can run smoothly and there's no other binding, then it's just set-up. The cable may have stretched - could be worth buying a new one.

I sort of know what I'm doing but couldn't get mine right after 2-3 hours of faffing about. Took it to my LBS who got mine changing gear like a rifle bolt after only 4 mins, and he oly charged me a tenner - far less than the hours of my own time spent on it.

[Jimbo.]

Gear cable and outer, definitely. After that, hanger alignment. I assume the drivetrain is clean, lubricated and in good order?

[minimoog]

Jimbo. said:

I assume the drivetrain is clean, lubricated and in good order?

New cable then yes? Difficult to do and set up (as indicated above) or readily DIY-able?

Thanks BTW

[Jimbo.]

minimoog said:

New cable then yes? Difficult to do and set up (as indicated above) or readily DIY-able?

Thanks BTW

Very, VERY easy. And bizarrely satisfying once you get it *just right*. Or maybe that's just me
You need:
Inner: http://www.chainreactioncycles.com/Models.aspx?Mod...
Outer: http://www.chainreactioncycles.com/Models.aspx?Mod...
End cap(s)
Ferrules: http://www.chainreactioncycles.com/Models.aspx?Mod...
Cutters: http://www.chainreactioncycles.com/Models.aspx?Mod...

You'd be best off the with cutters rather than normal side cutters and the like, as the latter crush the cables flat and then cut them, deforming them as they do. You can reshape them, but IME the proper cutters make a cleaner, "rounder" cut.

It's largely a case of:
Remove inner.
Remove outer.
Cut new outer to same length as old.
Fit ferrules to outer.
Fit outer to bike.
Thread inner through shifters, outer and mech.
Cut to length and fit end cap.
Adjust.
Sorted.

Edited by Jimbo. on Thursday 8th September 17:17

[Rocksteadyeddie]

As above likely to be a cable issue. Unless you have banged the derailleur heavily (falling off or being very careless) it is unlikely to be bent.

[walm]

If the cable has stretched then you don't necessarily need to buy a new one.
You just need to shorten its length to adjust for the stretch.

Just search for "derailleur adjustment" on youtube.

e.g. http://www.youtube.com/watch?v=2j1gSwhsVN8


IMHO there isn't something catastrophically broken about a stretched cable.
Mine stretches all the time and I just have to tweak the barrel-adjuster every couple of months.


If you can't get the derailleur working smoothly on your own with youtube's help - then replacing the cable isn't going to help because you STILL have to adjust the derailleur once you have installed the new cable.
Take it to an LBS before replacing the cable.

[budgie smuggler]

Also check that the drop out is still straight.

[minimoog]

Thanks for all the helpful suggestions everyone - lots of good stuff here.

[dome]

Quick way to check/clean the existing cables.

Get the drivetrain into 1st gear at the back-the biggest cog
Move the rapidfire shifter til it is in the biggest gear-7/8/9 but DON'T TURN THE PEDAL
This releases the tension on the cables so you can pull the outers out of their stops and check/clean/lube them.

This isn't as good as new cables obviously but may help you in the short term.

Brian