I've stretched alot of tires over the years mostly circle track dirt and asphalt late models. To get the right amount of stagger. The best time to get a tire to stretch is when there new. After they have been heat cycled it's alot harder to get much out of them. As stated before put about 30/40 psi in them and let them bake in the sun for an afternoon and put the right amount in and recheck.