Ford 2003 Mustang Workshop Manual page 115

Wheel and tire NVH concerns are directly related to vehicle speed and are not generally affected by
acceleration, coasting or decelerating. Also, out-of-balance wheel and tires can vibrate at more than
one speed. A vibration that is affected by the engine rpm, or is eliminated by placing the transmission
in NEUTRAL is not related to the tire and wheel. As a general rule, tire and wheel vibrations felt in the
steering wheel are related to the front tire and wheel assemblies. Vibrations felt in the seat or floor are
related to the rear tire and wheel assemblies. This can initially isolate a concern to the front or rear.
Careful attention must be paid to the tire and wheels. There are several symptoms that can be caused
by damaged or worn tire and wheels. Carry out a careful visual inspection of the tires and wheel
assemblies. Spin the tires slowly and watch for signs of lateral or radial runout. Refer to the tire wear
chart to determine the tire wear conditions and actions.