i am using a michelin m 12 rear, and i think a motion pro (?) rim lock. the lock is all rubber on the outside and its always tight, but i have torn the valve stem off of 2 ultra heavy duty tubes. and the tire is spinning on the rim again! both the valve stem and the rim lock are angled like they are twisting from acceleration. this is from one day at the track. is it the tire or the rimlock? or do i need to drill another hole and use 2 rimlocks?