I have recently began to feel a vibration in the steering wheel. I begins to appear at about 70mph and get worse as I approach 75mph. After 80mph it settles down but is still there. My first thought was a front tire out of balance. Took them to my local shop and had them rebalanced. They said they were not far off to begin with but did the balancing. I still have the vibration. When the wheels were off I checked the suspension and all looks normal, no loose bolts, worn bushings or cracking parts. Any thought on a cause/solution would be appreciated.