i work for discount tire and it sounds like it could be a balance issue. what kind of media did you put in the tires . but a balance issue will stay constant unless the speed changes. does the vibration stop after a different speed is met or is it a constant speed that the intervals are occuring. pm me for more details and advice
__________________
2001 2500 QC SB AT 4X4, 2'' level, Silencer Ring MIA, Dual 7" Miters, Aridog 100, new vp, Adrenaline w/ Pulse, smoke switch.