[Your Uncle Moe]

I had the SAME exact problem at the SAME exact speed. Heres how I solved it.

YES, it is a balancing issure. Dont listen to anyone who tells you that you dont need to balance your rear wheels. Because you DO. You need to go to Costco and get it Balanced there. At Costco they do it for 4.25 a wheel. Thats an awesome price. And they use those little weights which they hide inside where they cant be seen that well. Im 100% sure that will fix your problem.

Thats how I fixed my problem. The problem was actually from the rear wheels not being balanced well. But Balance the front anyway. Its only 4 bux. Just to be sure.

 

[Your Uncle Moe]

^Thats exactly what it is. But from what I know there are two kinds. Theres the kind where they place the weights on the very edge of the rim, and the other hidden kind where its inside the rim about underneath your rotors. You SHOULD have the little ones even on your rims. I bet the glue holding 1 or 2 of them probably gave out and the weight it was holding fell off. Just go get All 4 of your tires balanced at a reputable shop.