I have straightened steel rims, as long as they're not badly bent or creased. I don't think it would be a good idea on a sectional rim like a 2 or 3 piece.
Alloy rims- - - -that's another story. There are places like the one mentioned in the link above that specialize in alloy rim repair, but I'm sort of spooky about it. Trying to straighten a cast rim will probably result in hairline cracks and a possible rim explosion somewhere down the road. I think most of the repair/rehab places cut out damaged areas, weld in patches, and re-machine everything. That's probably safe.
Just for grins, figure out how many square inches of sidewall area a tire has, then multiply that number by 35, 45, 50, or whatever pressure the tire is rated for. It comes out in the tens of tons. That's the force pushing out against that rim flange. A cracked alloy rim, or a rusty multi-piece rim is a disaster waiting to happen. If your big rig with 2 or 3 piece rims runs 110 PSI tire pressure like most do, the force is a little over 60 tons, if I remember the math correctly.
Jerry
