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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?
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.
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.
