May be you tires are out of balance. In suggest you try some balance beads for those hi speed shakes. Remove your lead weights & put 1 oz in the front & 2 oz in the rear. If you still have the shakes ad 1/2 oz more F&R.... they're a PITA to put in, so just take you time, might try squeezing the tire so it'll suck in the beads, well worth the time & money,,,,,,,,,,,,,,,,,,,