Good afternoon! I am hoping for some advice regarding the dismounting of a fossilized old tire from the rim. My 1970 BSA Lightning rear wheel has a 40+ year old tire in place, size 4.00 x 18. No problem in separating the bead from the wheel rim, but there is no way my tire levers are going to stretch the bead over the rim. I have changed several tires in the past with no problem, but these aren't going anywhere. Any suggestions?