Vibration at Highway Speeds

This problem could be a result of:
1. Foreign material (mud, etc.) packed on the backside of the wheel(s).
2. Out of balance front tires or wheels. See Steering and Suspension, Wheels And Tires for the required balancing procedure.
3. Improper tire and/or wheel runout. See Steering and Suspension, Wheels And Tires for the required runout checking procedure.