I agree, new ones are the way to go. Acitone works though, an over nite soak and the will come off. Boiling them smells up the house and burns the hand. Baken works pretty good, 250 for 10 min, just turn the oven off once the tires go in. Preheat oven to 250, once the oven hits 250, turn it off, toss in the tires, 10 min later and they should pop off.
New ones are the best way to go.