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Rear Mech Wear

simonp123simonp123 Posts: 490
edited March 2012 in MTB workshop & tech
I have just swapped the rear mech from my old bike onto my new build. During this process i was giving it a good old clean and noticed how much wear has taken place on it already. The mech is less than 18 months old and has not done that many miles really as I've not been able to ride that much due to some issues.
The wear is in the piece that is between the front and back pieces of the hanger that the chain runs against, this has nearly worn right through :shock: The mech is Shimano XT Shadow. I reckon if I'd done as many miles as a lot of people do this would be gone inside 6 months.
Either I'm not keeping my chain as cleaned and lubed as I should be (and think I am) or this is a major weak point in this mech...

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  • supersonicsupersonic Posts: 82,708 Lives Here
  • The RookieThe Rookie Posts: 27,803
    Sounds like the chain has been routed the wrong side of the tab!
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • simonp123simonp123 Posts: 490
    supersonic wrote:
    Pics? ;-)
    Not yet. I'm not sure the camera on my phone will focus close enough. Might have to wait until the missus gets back from her trip with the SLR.
  • 386ka386ka Posts: 479
    Sounds like the chain has been routed the wrong side of the tab!
    This, really.

    The chain should not touch the tab, still, you would not be first one here to wear it through. :)
    A much loved, Giant Trance X3 2010
  • simonp123simonp123 Posts: 490
    386ka wrote:
    Sounds like the chain has been routed the wrong side of the tab!
    This, really.

    The chain should not touch the tab, still, you would not be first one here to wear it through. :)

    I don't think so, the wear is on the inside of the tab not the outside.
  • simonp123simonp123 Posts: 490
    edited March 2012
    I must admit I'm at a loss to understand what the tab is for unless it is there to knock back any stiff/locked links. It doesn't look like it has any structural use, so I guess it doesn't really matter if it does wear through.

    I guess if the chain is hitting it, the mech is either not made properly or I'm having some issues with the chain and my lubing/cleaning isn't good enough.
  • benpinnickbenpinnick Posts: 4,148
    Shimano changed the way the tab works about 5 years back. Chains now route (when routed properly) round what you would consider to be the outside of the tab, not the inside. Its only there to control the chain when it goes slack, so it doesnt double back on itself. Not really a big issue if its worn, but worth getting right any way.
    A Flock of Birds
    + some other bikes.
  • simonp123simonp123 Posts: 490
    benpinnick wrote:
    Shimano changed the way the tab works about 5 years back. Chains now route (when routed properly) round what you would consider to be the outside of the tab, not the inside. Its only there to control the chain when it goes slack, so it doesnt double back on itself. Not really a big issue if its worn, but worth getting right any way.

    Outside the tab?! Just to clarify, the tab I'm talking about is on the right of the pic here http://www.chainreactioncycles.com/Models.aspx?ModelID=20700

    My chain routes the same way as all the images I found on google. If the chain went the other side of the tab it would wear through in no time..
  • benpinnickbenpinnick Posts: 4,148
    Ahh, ok - Ive not seen that design before. All the XT mechs I have the arm as seen here: http://cycle.shimano-eu.com/media/techd ... 753789.pdf where the number 10 is pointing at. Yours looks like a not that important tab. On the XT mechs I have its about half way down, and switched sides a while back. If you've worn the one on yours, then maybe your chain is too slack.
    A Flock of Birds
    + some other bikes.
  • simonp123simonp123 Posts: 490
    benpinnick wrote:
    Ahh, ok - Ive not seen that design before. All the XT mechs I have the arm as seen here: http://cycle.shimano-eu.com/media/techd ... 753789.pdf where the number 10 is pointing at. Yours looks like a not that important tab. On the XT mechs I have its about half way down, and switched sides a while back. If you've worn the one on yours, then maybe your chain is too slack.
    The shadow ones are different.
    I'll check the chain slack, but I did the biggest chainring to biggest sprocket (no round the rear mech) then add 2 links method.
  • simonp123simonp123 Posts: 490
    Well... this is embarrasing. When I got home and had a look again I discovered that my rear mech did not have the tab like this one http://www.chainreactioncycles.com/Models.aspx?ModelID=20700, it was in fact like the previously posted link http://cycle.shimano-eu.com/media/techd%20...%20753789.pdf
    I guess they must have changed the XT Shadow since I bought mine.
    Even more embarasing was that when I looked at the wear, it was clear that I DID have the chain going the wrong side of the tab :oops: I must have routed it wrong the last time I put the chain on as I'm sure I had it the right way when I first fitted the mech.
    So mystery solved and I'm a twit :evil:
  • benpinnickbenpinnick Posts: 4,148
    Dont worry. I did it on my new XTR mech the other day. Seems shimano think its good to move the tabs and confuse us all!
    A Flock of Birds
    + some other bikes.
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