DIAGNOSE – CAR VIBRATES AT HIGH SPEEDS
by Jim Miller

SYMPTOM SUMMARY
There is a vibration or shimmy at high speeds. The symptom may get worse as the vehicles speed increases and may or may not be present at lower speeds.

USUAL CAUSE
The usual cause of a vibration or shimmy at high speed is improper tire balance or damaged tires.

DIAGNOSIS
Perform a careful visual inspection of each tire. Look for damage to the tires such as bulges or exposed steel belts. Inspect the wheels for dents, warpage or missing lug nuts. Check the tire pressure to ensure all tires are inflated evenly and to the correct pressure (check the owner’s manual for the correct tire pressure – it should also be marked on the side of the tire). If the tires are in good condition, the most cost effective diagnosis is to have the tires computer spin balanced. This can be done at any tire retailer for a nominal charge. If the problem still persists, further diagnosis on the drive train should be performed. On rear wheel drive vehicles the U-Joints should be inspected. On front wheel drive vehicles, the drive axles and CV Joints should be inspected. Inspect the CV boots for tears or other damage indicating excessive joint wear.