Tires: vibration/shimmy, warped rotors, cv joints

Question
Hello Mr. smith: I have a 1997 Pontiac Grand Am  and lately i have been experiencing a bit of what feels like vibration or shimmying as I accelerate...It levels off after 80 Km per hour (around 50 MPH  i assume). Just wondering if that sort of evidence would indicate wheel balancing as opposed to alignment (or maybe even something as unobtrusive as NOT using high performance gasoline, thus creating the impression of that sort of shimmy).
I would appreciate any information....many thanks.....MIller


Answer
Bob,

Tires out of balance (or out of round) generally cause a vibration in the 50 to 70 mph range (80 - 120 kph) and the vibration is pretty much there whether accelerating or braking or just cruising.

If a vibration only occurs when braking, then it's most likley warped rotors.

If a vibration only occurs when accelerating, then CV joints is most likely.

Hope this helps.