Shimano 2300 rear derailer problems - New problem!

kingofthetailwind Posts: 575
edited April 2013 in Workshop
Decathlon replaced my rear wheel a couple of weeks ago. Since then the rear derailer has been playing up. It will derail the chain to the right OK, but not to the left properly. I push the lever in, the derailer will move but the chain stays where it is and rattles. A second, half push on the lever will then derail it properly. Also the whole drive train sounded a bit rattley on Satuday, and the chain feels slack.

I've tried reading Sheldon's and Park Tools' pages on rear derailers, but have to admit I'm totally lost. Any pointers?


  • nicklouse
    nicklouse Posts: 50,675
    sounds like cable tension.

    but right? left?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Sorry, saying right/left isn't very useful is it! I'm a bit confused as to how gears on the cassette are described. The smallest gear in terms of size and the number of teeth is actually the biggest gear - as in harder to push and higher speed. :?

    It will shift to a gear with a smaller number of teeth OK, using the thumb button. But it won't shift the other way, using the brake lever.
  • sungod
    sungod Posts: 16,884
    assuming there's not something worn/faulty, probably you just need to turn the barrel adjuster on the rear mech to increase the cable tension slightly

    adjusters are notched, try turning it one notch at a time until you reach the point at which it shifts correctly, if you go too far, just turn it the other way

    an inelegant way of doing the adjustment is flip the bike upside down, then you can use one hand to turn the crank and the other to click the shifter while watching what the effect is
    my bike - faster than god's and twice as shiny
  • So I was thinking it was more complicated than it actually is! It was the limit screws that were putting me off trying this myself. I'll have a go tonight. Thanks guys.
  • So I've had a go at adjusting the tension which seems to have worked.

    But I now realise that only seven of my gears on the cassette are actually being used. The video below might help to explain what I mean.

    I start in the biggest cog, push the thumb shifter, it clicks but the chain doesn't move. On the the second click it starts to move but stops before the smallest cog. Moving the opposite direction the chain will go up to the biggest cog and there will be one more extraneous click.

    The small cog doesn't look like it's ever been used:


    Is this an easy fix?
  • onbike 1939
    onbike 1939 Posts: 708
    The tension on your cable is well out and the answer is to start from the beginning. With the gear selector on its highest gear sprocket (smallest cog), free the cable and rotate the crank allowing the chain to settle on the small cog. If it does not do this then the "H" screw needs unscrewing to allow the chain to move outwards. Now with the chain on this cog and the cable adjuster on the RD roughly half-way on the thread, tighten and clamp the cable (ensuring that it is in the correct place on the clamp). The cable should be reasonably taut in this position but now rotate the crank and adjust the cable tensioner until it moves one position up with one click. Now click the gear selector upwards one click at a time and check that all cogs are being selected. Fine tune the cable adjuster until it moves up the cogs smoothly and check the down-shift. If the chain hangs on the down-shift decrease the tension slightly (clockwise on the tensioner).
    Note: To increase tension turn gear tensioner screw anti-clockwise to de-crease, clockwise. Details can be found here for further info. ... derailleur
  • Thanks for that. I've been watching a few Youtube videos aswell, so I think I know what I'm doing now. Is it necessary to actually free the cable? Could you not just release all the tension using the barrel adjuster? I don't have a proper cable puller and have a habit of fraying cable ends with my pliers.
  • onbike 1939
    onbike 1939 Posts: 708
    It appears that your chain is not being allowed to move outwards enough to drop to the small sprocket so releasing all tension on the cable ensures that it's not the cable tension that's doing this. If you can completely slacken the cable by using the adjuster all well and good but you want the crew roughly midway in order to tighten or loosen the tension.
    Now it could be that it is the "H" screw that is stopping the RD from moving over to the small sprocket but before doing any adjustment best to lube the RD pivots and ensure the cable is free and lubed also. Sometimes winter muck can stop the RD from moving over its whole range.
  • owenlars
    owenlars Posts: 719
    If you release and refit the cable you can also wheel your barrel adjusters all the way in thus resetting the amount of adjustment you can get with them. I know it feels a bit leery taking the gear cable off but if you follow Onbike's instructions you will be ok. He has explained it very well.