I have reused U-bolts with out any ill effects. They were not 70 year old ones, maybe four or five years old, so no damage from weather. They torqued up just as tight and correctly as when I installed them.
I believe if the nuts come right off with little effort, the threads must be OK there for the u-bolt is OK. I have changed a lot of springs on school buses and trucks and have never seen nuts and threads cross thread or cut each other like some of the quotes above talk about. They have been rusted, but some heat and a impact gun backs them right off. I would change about half due to the length and rust. Big equipment uses extra long cut to fit u-bolts, and the torch was the cutter of choice, so getting the nuts past that was difficult. If they came right apart, they went right back together.
Joe
