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Adjusting rear derailleurs - aka "More stuff I should know how to do"

ProfessorTomahawk's picture

By ProfessorTomahawk - Posted on 27 January 2009

So, every time I get my bike serviced it shifts gears really smoothly - until I actually take it for a ride...

A few trips to the Dam later, the rear derailleurs don't seem to like changing gear as much - if I try to go up 1 gear, it just sits & thinks about it. Sometimes it'll sit there, waiting for me to forget about it, then suprise!! It changes up that gear...
If I ask it to go up 2 gears at once it's fine, but sometimes I *don't* want to go up 2 gears!!

I imagine that this is down to some part of the rear being a touch out of aligment - or something like that.

So, how do I adjust it? Ya?

My rear derailleur is Deore LX (No "just upgrade to XT" comments thanks Sticking out tongue)
And yes, I keep my chain lubed...


Stuart M's picture

You need a special tool to fix that, then again it might just be the cables need a little fine tuning after the service, particularly if they are new cables.

That said I have this trouble more with Shimano shifters than SRAM ones and I have been told by my LBS that you actually need to push past the click to get it to change properly. FWIW I think that is absolute S@#t, but it is what I have been told and it does seem to work. Makes no sense though, why have an indexed system if you have to push past the index to get it working.

Anyway, my thought son it. Good luck

Let there be light

Funkychicken's picture

but a quick fix would be to tighten your barrel adjuster a couple of notches

/edit: derailleurs (shimano or otherwise) should NOT "need" to be pushed past the click in order to work properly, if tuned correctly. If the "need" is there - cable tension is insufficient or the derailleur is not tuned properly.

hawkeye's picture

... too. Usually from bumping a rock or log with the RD on one of the tech bits of the Golf Course Singletrack.

I just stick the appropriate allen key from my multi-tool in the pivot bolt bend it back *carefully* and *slowly*, until the DR cage is again parallel to the rim when looking from the rear with the bike inverted. Usually this trailside running repair does the job and there's no need for later intervention.

It sounds agricultural - and probably is - but it's no different from what the LBS guys do with their "special" tool. The alu. alloy the DR hanger is made from is usually much softer than the rest of the frame, as it is designed to be a sacrificial part to save the frame from damage. Just make sure the DR pivot bolt is tightened up properly beforehand so that the force is shared by the base of the DR pivot assembly, otherwise you risk bending the hanger through the middle of the bolt hole and/or elongating the thread (not good).

Once you're done straightening, make shure you check the end points are still OK - you don't want the chain to come off the granny cog and into your spokes, or off the little cog to chew up your frame. Shift to the little rear cog, fully loosen off the tension at the shifter, take the slack out of the cable at the RD end, and adjust cable tension at the shifter to ensure accurate shifting and you *should* be done. Of course, all this assumes clean cables, clean chain, and straight chainrings and serviceable cassette.

Here endeth the lesson. Smiling We can talk further next time we hook up for a ride.

Rob's picture

If they replaced the cable inner this is not uncommon. Cables stretch after a short period of riding and thus need another small tweak. As others have said, a couple of twists of the barrel adjuster (not the limit screws) should fix that.

ProfessorTomahawk's picture

Thanks for the replies everyone! I'm thinking it could be cable stretch as the bike is still relatively new, so I'll give that a go - if that doesn't fix it, I'll take a closer look at some of these other options & see how we go.

Cheers Laughing out loud

...i've changed my mind...what have you done today?

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