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Indexing issue

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  • December 4, 2014 at 6:16 pm #22823
    Mother Theresa

    This is driving me berserk. On my spangly new Park stand the gears are perfect and shift seamlessly (one year old Forme Ax Edge Pro with Ultegra 10 sp cassette). Mount up and pedal away and I miss changes up and down – not always on the same shift – and only 1:20 probably go awry. What might be wrong?

    I’m new to bikes (after 30 years away) but have been known to strip and rebuild an engine with impunity so not a complete novice.

    MT

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  • January 26, 2015 at 6:15 pm #822633
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    allanj

    Even better!
    Even better!

    January 26, 2015 at 1:50 pm #822631
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    Mother Theresa

    Actually it never worked
    Actually it never worked properly so with this and a proper bike fit applied to it it is a new machine to me. Hurrah! <:P

    January 25, 2015 at 5:39 pm #822629
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    allanj

    Glad to hear it, so nice to
    Glad to hear it, so nice to have it all working again, isn’t it.

    January 25, 2015 at 12:55 pm #822627
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    Mother Theresa

    Just to complete this I have
    Just to complete this I have finally got round to changing the cable and it is almost perfect so thanks to all who commented.

    MT

    January 7, 2015 at 3:29 pm #822625
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    SilverMerlin

    To the OP are you easing off
    To the OP are you easing off pedaling when you change gear. This can make a big difference.

    I am new to road biking myself and had a similar problem with my bike on the front mech – the gears would change effortlessly on the bike stand but would be flaky out on the road. If you are happy that your derailleurs are set up correctly and the cable is sufficiently tight then It could be your technique rather than equipment is worth a try.

    January 7, 2015 at 2:04 pm #822623
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    DaveE128

    I suspect the problem is the
    I suspect the problem is the cable, and in my experience it’s most likely to be in the loop that runs round to the rear mech, (as it has the sharpest bends and is subjected to a lot of muck) but I’d change the whole lot if you can be bothered.

    The fact that the problem is with the highest gears is due to the fact that this is when the cable tension is lowest, so that is when friction (from tired cables) becomes most significant relative to cable force.

    I’ve found that tired cables can seem fine on the stand but erratic on these gears on the road/trail. I think that the extra load on the chain when actually pedalling the bike along is enough to make the difference between shifting and not shifting.

    If you have external cable routing you can check the cable by shifting to the highest gear (smallest sprocket) then without moving the pedals, shift the shifter into the lowest gear, so the inner cable goes slack. Now unhitch the outer cable from the frame stops, and you can slide it up and down to assess the friction. You can also use this opportunity to help move a little light lubrication along the inside of the cable outer to give a quick temporary improvement.

    January 7, 2015 at 11:27 am #822621
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    Mother Theresa

    I’m not sure I know what you
    I’m not sure I know what you mean here, the chain stops perfectly at 1 & 10 with no over-runs if you mean the travel limiting screws. Apart from the actual cable clamping screw I don’t remember any more but am at work so not able to look at it just now.

    January 7, 2015 at 10:41 am #822619
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    JonD

    Has anyone mentioned the
    Has anyone mentioned the outer/small cog side screw stop ? – if that’s out then you’ll never get shifting spot on. My recumbent has a longish enclosed cable run, and like a few others – possibly with bar end shifters – seems particularly sensitive. Make sure there’s no cable tension when setting it, tho.

    January 7, 2015 at 9:54 am #822617
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    crikey

    Try not to get mugged into
    Try not to get mugged into paying a million pounds for cables; there are different price points but it’s better to be able to change them when they are worn rather than thinking ‘I paid a million pounds for these cables, they’ll do for another month’…

    January 7, 2015 at 7:50 am #822615
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    Mother Theresa

    Thank-you all.
    Are all
    Thank-you all.

    Are all cables created equal? Not unsurprisingly there isn’t a buyers guide here or elsewhere for gear/brake cables.

    MT

    January 6, 2015 at 10:30 pm #822613
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    allanj

    Just put a new cable on my
    Just put a new cable on my bike, the difference is unbelievable. Shifting seemed erratic before, now I realise that it was also stiff and rough. So much better with a new cable!

    January 6, 2015 at 9:36 pm #822611
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    DanTe

    Have a wiggle of your
    Have a wiggle of your cassette. Might be a bit of play in the freehub. Got exactly this problem at the minute in the middle of a week on the bike in S.Spain.
    Maybe check that the cassette is tightened on properly?

    January 6, 2015 at 9:04 pm #822609
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    crikey

    99% of shifting problems are
    99% of shifting problems are related to cabling, not chains. The current fashion for checking chains has only been around for a couple of years, and everyone managed perfectly well for the last 30 or so years without changing chains every two minutes. (I have cassettes and chains that get run into the ground, and indexing is never a problem , however worn they are.)

    Try new cables, and most importantly, check that the loop of cable next to the rear derailleur is long enough; as the derailleur moves across the block, any lack of length can cause issues.

    Also check that the cables are long enough when they are wrapped on the bars and when the bars are turned.

    Re-cable without wrapping your bar tape; just stick it down with insulating tape and try it out on the road first.

    January 6, 2015 at 6:26 pm #822607
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    Mother Theresa

    Changed the chain (0.75%
    Changed the chain (0.75% stretch), no improvement.

    Cables next; I’ll let you know….

    December 7, 2014 at 11:36 am #822605
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    matthewn5

    Use a steel rule or tape
    Use a steel rule or tape measure. Edge to edge of 12 complete links on a tight chain should be exactly 12″ or 304.8mm if you’re going all metric.

    Chain checkers only measure over 6″ or so, so you don’t get such an accurate result, and can be inaccurate for a variety of complex reasons, see http://sheldonbrown.com/chains.html#stretch

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