Front Suspension problems of the 1998 Oldsmobile 88

The front end was vibrating . The vehicle was taken to merchants tire for alignment and rotation. I was advised the tire were chopped up and new tires were the only way to fix the problem and the problem was caused by weak shocks or struts. I took the car to the dealer and was advised by the service dept. Personal that the tires needed to rotated every two oil changes and nothing was wrong with the shocks or struts. Also I was advised that if they were rotated they might wear smooth and the problem would go away. ( dot number: tire size: p205/70r15 ).