Question

When on the freeways my car is unsteady between speeds 55-68mph, it seems smooth again around 70mph and upwards. I've not had this problem before. About 2 weeks ago I went through a pot-hole. I mentioned it to my new garage mechanic and he recommended balancing the wheels, which he did and mentioned moving a better wheel from the rear to the front. (I own a Saturn 1997 small four door). He also recommended wheel alignment done by a man he uses. My first freeway drive my car felt as though it was on ice, it felt as though it was not connecting with the road and at 60-65 the steering wheel was shacking. I took it back to the wheel alignment guy who said if the steering wheel was shacking it was a balance problem, but mentioned he'd put 45lbs in the tires. I returned to my mechanic who said it was the high air pressure. He lowered the pressure but it still bounced. After much talk I purchesed 2 new front tires. I drove on the freeway and still have some shacking of the car.