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Index problems

hellsteeth54hellsteeth54 Posts: 111
edited May 2009 in MTB workshop & tech
Over the last couple of months the indexing on my rear mech has got steadily worse. I've adjusted them quite a few times, but its never spot on, and doesnt stay right very long.

A few weeks ago I took to LBS, he seemed to sort it (as well as confirming that nothing was damaged or bent), but again the indexing was out after a couple of rides.

So today I changed the cables, inner and outer, the old ones were pretty rusty so thought that was obviously the problem. But I still can't get the gears right!

I'm using the Park Tools book, which is a pretty thorough guide. Starting on the smallest cog, I then change down a gear, rotate barrel adjuster counter clockwise till rattle is heard, back off, then down to next gear, and repeat. This is fine all the way down to largest cog, but when I start to go back up the gears, they either dont change, hesitate, or seem to be a gear behind where it should be. This is pretty much what was happening before!

Confused?? I am! :evil:

The bike is a GT Avalanche2, '08. Gears are Alivio shifters and Deore mech, and new cable is Transfil Black Snakes.

Any ideas what I'm doing wrong?

Posts

  • nicklousenicklouse Posts: 81,520 Lives Here
    which way does the cable move the mech?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • supersonicsupersonic Posts: 82,708 Lives Here
    Assuming nothing is damaged, then it still sounds like cables - dodgy routing, frayed outers? Does the inner run through smooth?

    They also bed in so will need readjusting. An 1/8th of a turn can make a difference.

    Also ensure the limit stops are properly set.
  • nicklouse

    The cables pull the mech to the larger cogs. So the problems arise when tension is released.

    supersonic

    I've changed the outers too, and paid attention to making sure the cut ends were rounded out after cutting. I copied the routing from the old outers, and same lengths, except the piece which goes into the mech, which I made slightly longer (maybe 20mm), to make a straighter entry into barrel adjuster.

    Speaking of barrel adjusters, I have one on mech and shifters, should I leave one alone and just use other?
  • supersonicsupersonic Posts: 82,708 Lives Here
    Set them both in the middle, pull the cable through fairly tight when on the small cog and high gear at the shifter, reattatch, fine tune at the mech, then tweak at the bars when riding if tension shifts.

    Does the mech spring back to the stop fast?
  • supersonic wrote:
    Set them both in the middle, pull the cable through fairly tight when on the small cog and high gear at the shifter, reattatch, fine tune at the mech, then tweak at the bars when riding if tension shifts.

    Does the mech spring back to the stop fast?

    Ok that sounds good I'll have a bash tomorrow. Yeah mech springs back quickly.

    Actually one thing I did notice now you mention it- with small cog engaged, I could only change maybe 3 clicks on shifter (while NOT pedalling) before it became too tight, I'm pretty sure I could move it the whole range before. Have I done something wrong?
  • supersonicsupersonic Posts: 82,708 Lives Here
    That sounds better - sounds like there was hardly any tension before! The chain will stop the mech moving of course and the tension will ramp up.
  • Yep that makes sense!

    Ok thanks for the replies, I'll try setting it up again tomorrow using your method supersonic and see how it goes, cheers!
  • Just an update...

    Reset everything, and started from scratch, with barrel adjusters in central position. Had same problems to start with, but with a bit of perseverance everything is bang on now.

    Eventually I gave up with the Park method tho, and just tried all the gear combos with middle chainring selected, instead of largest as they suggest. This seemed to get the best results all round.

    Went on to change front cable inners and outers, that was a piece of cake! :D

    Thanks for the advice, as always.
  • Chaz.HardingChaz.Harding Posts: 3,144
    If you still get problems, maybe it's your shifters.

    How old are they? And have they been hammered in muddy and wet conditions?
    Boo-yah mofo
    Sick to the power of rad
    Fix it 'till it's broke
  • hellsteeth54hellsteeth54 Posts: 111
    I took the covers off the shifters while doin this job (mainly cos I had no idea how to get the cable out...), and they seem pretty good. About a year old, and yeah have seen a lot of mud and water, but I gave them a wipe and a quick squirt of teflon magic spray. They feel fine anyway.

    To be honest, I'm a bit worried about these cables, wish I'd gone for XTRs now. These outers seem really flexible compared to the old ones, surely that will affect shifting?
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