Light spoke rubbing of rear mech

EH_Rob
EH_Rob Posts: 1,134
edited January 2013 in MTB workshop & tech
I changed the jockey wheels on an sram x0 mech last week without issue (the stock sram ones were toast, replaced with KCNC). Its a 1x9 setup. The old wheels sat in little sleeve type things which I transferred to the new ones. With the bike upside down I checked to see if all was working as it should, which it appeared to be.

When riding the bike, I've noticed that when in the lowest gear, the back of the mech is pinging against one of the spokes as the wheel turns. Just one, and only a tiny bit. This definitely did not happen before. The actual shifting and indexing is fine on all gears. I've tried adjusting the limit screw to shift it away but it still seems to be happening. I'm going to check a few things tonight to see if I can get to the bottom of it, and just wanted to see what you think could be the problem. Here's a few I thought of. What do you think?

1. Bent mech hanger
2. Bent mech
3. Jockey wheels for some reason not compatible or installed correctly (no arrows or markings on them)
4. Wheel not seated correctly

1 is possible
2 is probably unlikely as the shifting wouldn't still be working would it?
3 is possible
4 is possible, unlikely and easily checked

Comments

  • njee20
    njee20 Posts: 9,613
    Unrelated to jockeys, they'd not affect position of the mech relative to the spokes.

    I'd be looking at why it's only 1 spoke, but assuming your mech is set up correctly, that's not right.
  • cooldad
    cooldad Posts: 32,599
    Either one weirdly bent spoke - unlikely. Or maybe the cable end touching a spoke.
    It would seem impossible for the mech to touch a spoke and the indexing to be right. Not to mention imminent disaster.
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  • bennett_346
    bennett_346 Posts: 5,029
    Wheel not seated properly/out of true i'd say. If the indexing is correct then neither the limit screw or mech hanger are wrog/bent, and if its only touching one spoke that would lead me to believe the wheel is moving laterally towards the mech at one specific point, hence it being possible out of true.
  • Ouija
    Ouija Posts: 1,386
    Could also be dished incorrectly or a bent mech hanger.
  • bennett_346
    bennett_346 Posts: 5,029
    Ouija wrote:
    bent mech hanger.
    Wouldn't explain why it only hits one spoke though could be a combination for sure.
  • mcnultycop
    mcnultycop Posts: 2,143
    Is it the same spoke every time? Could it be a sticky chain link knocking the mech out?
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  • EH_Rob
    EH_Rob Posts: 1,134
    Solved. I shouldn't have put the little sleeve things that the old jockey wheels were sat in back in with the new ones. They were making the cage too wide, which was causing a lack of clearance between the cage and spokes. It was actually the cage that was rubbing the spokes rather than the mech body itself. The reason I decided to put them back in was because the jockey wheels didn't seem to sit straight without them, but tightening the cage bolts lines them up perfectly.

    Still not sure why it was one spoke though. Checked the wheel and it seems fine, spoke tension ok and although not perfectly true well within limits. Was seated correctly too. Seems ok now, will take it for a quick ride down the road tomorrow to make sure.

    Ta for your help all.
  • Manc33
    Manc33 Posts: 2,157
    Same happened to me after *something* hit my back wheel.

    Same as this, one spoke, only rubbing very lightly, in the lowest gear.

    Painted a bit of Tipp-Ex on the offending spoke, got a spokey and straight away I found the nut of that spoke to be "finger loose", plus turning it to "tighten" the nut (thus loosening the spoke on "this" side, lol) was the right way to bring the wheel away from the rear mech, at that point on the rim. I also did the opposite on the other two spokes on each side of it on the other side to try to even it out a bit.

    Eventually I got the spoke to be something like the same distance from the rear mech as the other spokes and keeping the wheel true at the same time... although the spoke is bent and is still closer than the other spokes, it needs replacing really.

    I will also try to adjust the screw to bring the rear mech away, even just 1mm will make it stop brushing on the mech, but keeping it able to change up to the biggest sprocket. Since it was one spoke, I never even thought to do that. :oops:

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