Been having a major problem on my road bike. It seems that no matter how tight or secure I close my rear wheel's quick release, after a while when I start downpedaling, the rear wheel goes out of alignment, angled towards the left, and the tire starts rubbing against the frame. It's driving me crazy. I had the wheel trued a couple months ago. Any suggestions?

This been discussed over and over again, I think once this week even. A search would have yielded plenty.

But anyhow:
1) check that your axle isn't protruding past the outside face of the dropout. If it does, readjust, or add washer inside locknut. If you need to add a washer, do it on the non-drive side, or be prepared to readjust the shifting.
2) check that your q/r springs are correclty orientated, pointy end inwards. Or remove them.
3) check that the outside face of your locknuts are properly serrated. If they're worn smooth, replace. If replacing is somehow difficult, you can use a centering punch to punch dimples into the outside face, or a chisel to create some grooves and ridges.
4) If your q/r has external cam, replace with an internal cam, steel q/r. Stock Shimano ones do fine.

1 to 3 make sense to me. I can't quite see how #4 helps. I'm missing something - are internal cam qrs stronger somehow?

They provide more clamping force. Read https://www.sheldonbrown.com/skewers.html for an explanation.

Was there anything particular that happened to necessitate the wheel truing, such as an accident or derailleur into the spokes? Distortion of the right rear dropout can cause a poor grip of the axle.

I replaced a Mavic external cam skewer with a Shimano. That solved the same problem for me.

Could be the dropouts are worn or misaligned.

External cam QR's work okay actually - but are often of alloy construction for the lever, nut and facings - the serrations wear away quite easily. When used with horizontal dropouts - they suck period. They're really intended for modern day vertical dropouts.

So if you have horizontal dropouts - switch to classic steel quick releases - Shimano, Quando, etc...

Also, one more thing. When you had the wheel trued, did you have the wheel dished properly? Because if the wheel was off-dished to the left side, then you have been forcing the wheel to the right to center it while clamping down the quick release. The wheel under load will naturally want to settle back into the parallel plane of the dropouts resulting in the wheel moving left and closer to the non-drive chain stay.

So check the dish of the wheel while you are at it...


=8-)

That's the real essence of the problem. External cam "boutique" skewers are lighter and are adequate if used with vertical dropouts. The provide insufficient clamping force when used with horizontal dropouts.

Shimano skewers get my vote.