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Rear mech / derailleur indexing & skipping gears

JameyJamey Posts: 2,152
edited December 2008 in The workshop
I've just fixed a problem I was having with the rear mech indexing which was driving me nuts and I'm posting this thread just in case it helps anyone else out in future, although I'm probably kidding myself given the search facility on these forums, but still...

Yesterday I cleaned the bike, which included removing the rear mech for a complete clean and re-lube. When I put it back on I re-indexed it and noticed that some of the gear changes (both up and down) were a little stickier than they were previously but it was getting late on a Sunday evening and I figured it was good enough to ride so I left it and made a mental note that I might need a new cable sometime soon.

Today, on the journey to work, the problem manifested itself a bit more clearly and I found that I couldn't actually use fifth gear (it's a nine-speed btw) at all. If I changed up from fourth into fifth then the chain rattled a little and then changed up again into sixth. And if I changed down from sixth into fifth then again the chain skipped two places instead of one, ending up in fourth. The changing at both of the extreme ends of the cassette (first <--> second and eigth <--> ninth) was fine, by the way.

It wasn't a show stopper but, as I'm sure you can imagine, it was bloody annoying so halfway through the commute I stopped to adjust the tension. I tried it both ways (tighter and looser) and neither made any difference. When I got to work I was a little early so I turned the bike over, detached the cable and tried to index it once more. The same problem happened again. I even tried adjusting the 'B' screw but, perhaps predictably, that didn't help.

It got to the point where I was just standing there in despair, looking at the bike with my brain completely empty. And as is so often the case when you get to that stage, suddenly everything became clear. Maybe you have to go completely to your wit's end in order to actually clear your mind enough for the solution to pop in there but whatever the reason, I took one look at the way the cable was attached to the mech and hallelujah.

I had clamped the cable on the wrong side of the pinch bolt, so instead of running in a perfectly straight line from the housing into the mech's clamp it was coming out at an angle.

Once I rectified that everything started working again.

So hopefully if someone ever searched for "rear mech indexing" or "skipping gears" they'll find this in future... Even if it is fifteen pages deep into the search results due to the stupid chronological (as opposed to being based on relevance) way the forum returns search results.

Posts

  • robbarkerrobbarker Posts: 1,367
    An easy error to make, but a lot of mechs change their cable pull if you clamp the cable wrongly (some deliberately in fact) and you'll never get the indexing right then.

    The solution, as with a lot of things, is to "darllenwch y llawlyfr ffwrcho" as we say in Wales, or RTFM in English.
  • robbarker wrote:
    An easy error to make, but a lot of mechs change their cable pull if you clamp the cable wrongly (some deliberately in fact) and you'll never get the indexing right then.

    The solution, as with a lot of things, is to "darllenwch y llawlyfr ffwrcho" as we say in Wales, or RTFM in English.

    Ffwrcho, eh? That's a new one to me. I prefer 'penci' myself, but that comes from a youth of watching C'mon Midffîld.

    Sadly, so many goods (in general) these days come with no real documentation. The only way you'll get a proper meaty instruction handbook these days is if it's got the same thing written in all the languages of the EU in it! :x
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