My front wheel is not straight in the fork dropouts. It's been like this since I've bought the bike second hand a few years ago. See pictures below.
I've tried installing an identically sized wheel from a different bike with the same result, I've also removed the brake rotor from this wheel and installed it the other way round. Once again the left side had less clearance, and so I conclude it's a fork/dropout issue and not wheel dishing. If it matters, it's an MTB fork with shocks and a QR skewer.
Another problem I've always had with this bike is that I could never align the front brake caliper in such a way that the (disc) brake wouldn't rub. I did the usual "loosen caliper, hold brake, tighten caliper" procedure, and while it worked with other bikes, here it never quite helped. I could actually see that the caliper was centering itself around the rotor correctly when the brake was pulled, but then as I tightened the bolts, they were moving the caliper to a slightly different position, thus causing the rubbing.
I wonder: since the dropouts are not straight and the wheel is not mounted fully straight (the plane of the wheel is not fully perpendicular to the ground), does this also mean that the hub and so the brake rotor are not straight either? Could this be causing the rub?
I talked to my local BSO and they were adamant that the issues are not related, and that the rotor is straight because it's attached to the hub. But to me if the dropouts are misaligned, then the whole thing, including the hub, will be tilted. Am I correct?
Below is a drawing of my understanding of how this would work. I've marked the rotor as green.