WHEEL ALIGNMENT 2B-5
VIBRATION DIAGNOSIS
Wheel imbalance causes most highway speed vibration
problems. A vibration can remain after dynamic
balancing because:
lA tire is out of round.
lA rim is out of round.
lA tire stiffness variation exists.
Measuring tire and wheel free runout will uncover only
part of the problem, All three causes, known as loaded
radial runout, must be checked using method of
substituting known good tire and wheel assemblies on
the problem vehicle.
Preliminary Checks
Prior to performing any work, always road test the car
and perform a careful visual inspection for:
lObvious tire and wheel runout.
lObvious drive axle runout.
lImproper tire inflation.
lIncorrect trim height.
lBent or damaged wheels.
lDebris build-up on the tire or the wheel.
lIrregular or excessive tire wear.
lImproper tire bead seating on the rim,
lImperfections in the tires, including: tread
deformations, separations, or bulges from impact
damage. Slight sidewall indentations are normal and
will not affect ride quality.
Tire Balancing
Balance is the easiest procedure to perform and should
be done first if the vibration occurs at high speeds. Do
an off-vehicle, two-plane dynamic balance first to correct
any imbalance in the tire and wheel assembly.
An on-vehicle finish balance will correct any brake drum,
rotor, or wheel cover imbalance, If balancing does not
correct the high-speed vibration, or if the vibration occurs
at low speeds, runout is the probable cause.
