Forum home Mountain biking forum MTB workshop & tech

Problem indexing rear gears

jndb72jndb72 Posts: 629
edited August 2012 in MTB workshop & tech
Afternoon,

I've tried indexing my rear gears for the first time this afternoon following the instructions here http://www.parktool.com/blog/repair-help/rear-derailler-adjustments-derailleur

I can go from the smallest cog to the largest without too much trouble with the gear changes being quite smooth. However, when I try changing from the largest cog down one gear nothing happens. When I change again the chain moves to the next cog but them I'm a gear out.

Could this be down to a dodgy inner gear cable which needs replacing?

The rear mech is a 10 speed Shimanno SLX.

I've done the re-indexing with the chain on the biggest chainring at the front. Is this correct?

Thanks
2011 Canyon Nerve AM 5.0
2009 Specialized Rockhopper Disc

I might have alzheimer's but atleast I don't have alzheimer's

Posts

  • nicklousenicklouse Posts: 50,675 Lives Here
    mucky cables or poor routing adding friction to the system.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • jndb72jndb72 Posts: 629
    So strip and clean the cables (inner and outer) and try again?

    If this fails replace the cable?

    Thanks
    2011 Canyon Nerve AM 5.0
    2009 Specialized Rockhopper Disc

    I might have alzheimer's but atleast I don't have alzheimer's
  • mister pmister p Posts: 405
    I wouldn't waste my time cleaning them personally. Get a length of decent outer (Shimano SP41) and a decent inner wire and replace yours.
  • nicklousenicklouse Posts: 50,675 Lives Here
    mister p wrote:
    I wouldn't waste my time cleaning them personally. Get a length of decent outer (Shimano SP41) and a decent inner wire and replace yours.
    +1
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • jndb72jndb72 Posts: 629
    Was thinking of replacing the inner and outer cables but they both only got replaced by the LBS about 8 weeks ago.

    Gonna have a bash at doing it myself this time.
    2011 Canyon Nerve AM 5.0
    2009 Specialized Rockhopper Disc

    I might have alzheimer's but atleast I don't have alzheimer's
  • Chunkers1980Chunkers1980 Posts: 8,035
    If they did it properly then it won't be that then.

    Make sure the shifter is fully clicked out (where you can only draw cable in) when you start the setup.
  • mister pmister p Posts: 405
    If they did it properly then it won't be that then.

    If they used cheap nasty cables then 8 weeks is plenty of time for them to have gone bad.
  • Chunkers1980Chunkers1980 Posts: 8,035
    Would a shop really buy in nasty cables as you say?

    What is a nasty cable? Even 99p Wilko ones are ok.

    I'd say it is more user error. The problem occurs in big front and big rear, a combo you shouldn't use (if OP has a 3x chainset)
  • jndb72jndb72 Posts: 629
    Yep it is a 3x chain set.

    Only using big front and big rear because that's what was suggested in the documentation I read. It's not a gear combo I would use while out riding. Plan on going for a quick ride later so I'll see how they feel then.

    Not sure what inners\outers the shop used when they changed them. In all fairness they did work perfectly for a good few weeks, then gradually they started slipping etc.

    Cheers
    2011 Canyon Nerve AM 5.0
    2009 Specialized Rockhopper Disc

    I might have alzheimer's but atleast I don't have alzheimer's
  • DmakDmak Posts: 445
    Surprised no one has mentioned... After you clean, lube and insert.....into outer.
  • jndb72 wrote:
    Was thinking of replacing the inner and outer cables but they both only got replaced by the LBS about 8 weeks ago.

    Gonna have a bash at doing it myself this time.


    Check how freely the cables run, could well be one of the outers is pinched where it was cut, could be worth trying to open it up a bit with a metal pointy thing (like a scribe if you have one) if you find any to be tighter than the rest.

    Anyone who has ever cut cables knows that cutting the outers can be a real pain if your tools are a little blunt
    Bikes:
    Cannondale Killer V 1995 (Promo model) - My first Race bike now converted to a commuter
    Lapierre X-Flow 712 - XC fs rocket
    Pivot Mach 6 - Enduro Machine
    Pinarello FP2 - Roadie
  • Hi

    You should never run big to big or for that matter small to small. Does the problem occur when you run middle and small chainrings to biggest cassette ring? If not I wouldn't worry too much but if the problem still exists then I'd check out the Shimano Tech docs for your setup and follow the setup instructions from scratch for the rear mech and indexing. Make sure your rear mech 'stops' are set correctly, the mech is correctly positioned and outer cable not too tight a loop where it runs the the mech itself. Also check that the mech and hanger is not bent.

    It should be possible to get the shifting spot on by following each step carefully.
  • jndb72 wrote:
    Yep it is a 3x chain set.

    Only using big front and big rear because that's what was suggested in the documentation I read. It's not a gear combo I would use while out riding. Plan on going for a quick ride later so I'll see how they feel then.

    Not sure what inners\outers the shop used when they changed them. In all fairness they did work perfectly for a good few weeks, then gradually they started slipping etc.

    Cheers

    Big ring and big sprocket is worth testing as if selected inadvertently it could cause jamming. I can't think of any other reason for working with that combination.
    If it is not down-changing and the cables are in good nick then the cable may be over-tensioned. Start off my making sure the Rear Der is lubricated at all pivot points. Screw cable tensioner to mid position with cable uncoupled and then pull cable to reasonable tension before clamping. If the chain moves up the block one position when the pedals are turned without you moving the gear selector then this is a good starting point. Screw the tension screw clockwise a half turn at a time until chain remains on small sprocket but will move up one when this is selected. The final adjustment is not far away at this stage.
  • jndb72jndb72 Posts: 629
    Good news, well for me at least.

    Stripped, cleaned and lubed the inner and outer cables, re-indexd and the gears are now working better then when the LBS done the last re-index. Will defo be doing this myself in the future.

    Thanks for the helpful tips and advice.

    Cheers
    2011 Canyon Nerve AM 5.0
    2009 Specialized Rockhopper Disc

    I might have alzheimer's but atleast I don't have alzheimer's
Sign In or Register to comment.