had and fixed a similar problem cept mine was at 54mph and stopped around 65. Mine was a tire balance problem and getting it done did wonders. Have to ask-did they use a bubble or spin balancer, 2 front or all tires, and did they know what you were trying to fix? reason i ask-spin in my mind is better as it should involve both sides of the tire where as bubble is basically just 1 side. Was it done by some who seemed to know what he was doing or did he look like a mcDonnalds Tech gradiuate? And if they did not know what the problem you were trying to fix, they may not have been that precise. I only had the front done and it fixed the problem, but if it had not I would have gotten the rear done also. Not sure how much rear out of bal would affect things but kinda think it would being such a short wheel base. Like in the link-start with the basic stuff and 9 out of 10 times it will be something simple and it saves alot of time and $$. Next step would have been in for an alinement and sure any other problems would have been caught and also fixed.