Well, maybe more like: "how to jerry-rig something so that your bent fender doesn't rub on your tire (without spending any money)." This is a problem I'm having with the new old Schwinn Suburban. The old Schwinns were designed so that the fenders fit very closely around the tires. This is a nice aesthetic touch, but it also means that any little bend or tweak in the fender or its supports can put the inside of the fender in contact with your tire, causing undue wear and tear on the tire, and undue frustration when peddling (plus a really annoying rubbing noise).
I've been trying all sorts of ways to bend the fender out where it is rubbing (at the very back of the fender), but all to no avail. The fender itself is not noticeably bent, but I think the support is tweaked a little. The problem is where the fender support is attached on the inside of the fender (see arrow on picture above). The tire is actually rubbing on the support piece, not the fender itself. I considered taking the support off, but then the fender would flop about and rub on the tire anyway. Soooo, long story short, I think I solved the problem with a couple short pieces of plumber's tape (the metal kind) and some bolts salvaged from old brake shoes. Basically, I just used the bolts to fasten the pieces of plumber's tape on as extensions for the support arms where they bolt on to the frame (circled on the photo above), making the support arms longer and forcing the fender out away from the tire a little more. The photo below shows my Frankensteinesque innovation.
Obviously, you don't have to use salvaged bolts from brake shoes if you have suitable bolts laying about, but I didn't. Plus, it's a good reminder to save everything, because you can probably find a use for it later. I don't know how well this fix is going to work in the long run, but it all seems pretty stable for now. Of course, the front fender is rubbing too, but I think I can just bend that one out.
PS--If you use metal plumber's tape for anything, you'll need a pair of aviation snips to cut it, available at any hardware store.