Originally Posted by
PennStan
Update. Checked and re-checked all the great suggestions provided here. Nothing found. Spent a good amount of time on the issue yesterday - ride hill outside house, wheel shifts, walk it back to garage, inspect. Repeat many times with wheel shifting EVERY time. For the life of me I do not see how the wheel can shift with it clamped down so hard! Then tried measuring whether wheel was centered and parallel to frame. My thought was that maybe the wheel is cocked when fully inserted into the dropout and it's just trying to right itself. Determined (don't ask how) that the non-cog side could be out from the bottom of the dropout a couple mm. Clamped it in and tested. No movement. Retested and retested - no movement. Went for a 30-mile ride trying to really work up hills - no movement. I have no reason to believe the frame or wheel is bent. As an engineer, this is bugging the heck out of me.
Just for grins, try removing a mm of axle on either end with a grinder, cut off wheel, etc. It really is beginning to sound like the axle may be a bit long and that although you are closing the QR skewer fully and tightly, it is contacting the end of the axle partially and the frame partially. Fit the wheel without the skewer through the axle and try to use a clamp to make sure drop outs are tight on the lock nuts on the axle and see if any axle is protruding past the face of the drop out. If so, you QR is clamping on the axle and not the frame.