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I have an old Trek T-900 tandem that my wife and I ride quite a bit. It's got an 8-speed rear setup.

It's a standard (tandem) 145mm rear-spacing with matching hub, but tightening down the quick-release moves the derailleur hanger, screwing up the shifting. I can re-adjust, but next time I remove the wheel, it shifts poorly until adjusted again.

This is an aluminum frame, so re-spacing it isn't an option. Ideas of what is going on here?

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  • Is it a removable/replaceable hanger? Or is it integral to the frame/dropout?
    – stranger
    Aug 25, 2014 at 14:24
  • I'm pretty sure it's removable. I'll look when I get home. Aug 25, 2014 at 14:24
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    If it is removable, I would check that it is still bolted securely in place. It's pretty common that removable hangers sort of overlap with the dropout. So it's possible that the hanger is loose, and the QR is then clamping it firmly in to place, but then each time you remove and reattach the wheel it clamps in a slightly different position. That's my first thought.
    – stranger
    Aug 25, 2014 at 14:27
  • Are you tightening down the QR too much?
    – Batman
    Aug 25, 2014 at 16:21

2 Answers 2

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Edited from my comments above:

The first thing I would check is whether the hanger is removable.

If it is removable, I would check that it is still bolted securely in place. It's pretty common that removable hangers sort of overlap with the dropout. So it's possible that the hanger is loose, and the QR is then clamping it firmly in to place, but then each time you remove and reattach the wheel it clamps in a slightly different position. That could explain the tricky shifting.

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  • It is a removable hanger. It's either bent, or the frame is. I guess I'll source another hanger and hope for the best. Aug 25, 2014 at 20:39
  • I think a new hanger should work. The whole point of replaceable hangers is that they fail before the frame fails, and then you can fix it with a $10 part instead of a new frame. If the new hanger fixes it, I would go ahead and order a second one, and just leave it in your tool box. You never know how hard it'll be to find one next time you need one.
    – stranger
    Aug 25, 2014 at 20:42
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I put a new hangar in place, and it did not fix the issue.

Taking a closer look at things, it appears that this "tandem hub" is a standard 135mm hub with spacers to widen it out to 145mm. The hub is old and worn and one of the cones is bent.

I serviced the hub to the best of my ability. I can't identify the hub to replace the cone. After putting everything back together, the hangar/frame/derailleur still bent inward, but only about half as much as before.

I put a washer on the non-drive side of the hub to space it a little more. This appears to have fixed it. It'll take a few more miles to tell. A new wheel is in my future.

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