Vibration Analysis

^ Vibrations that are tire or wheel induced may be caused by two factors: balance or runout.
^ Low-speed vibrations, those which occur at less than 40 mph, are usually related to runout. Highway speed vibrations, those which occur at greater than 40 mph, may be caused by either imbalance or runout.

The procedure outlined here matches with the Vibration Diagnosis flow chart. When you become familiar with this procedure, it will be possible to go directly to the flow chart to systematically diagnose and correct a tire/wheel induced vibration.

(1) VISUAL CHECKS

^ Ensure that tires on the same axle match in size and type.
^ Proper inflation pressure.
^ Proper tire bead seating on rim.
^ Irregular or excessive tire wear.
^ Damaged wheel or tire.
^ After market wheel nuts and anti-theft lock.
^ Loose or missing wheel weights.

(2) Complaint definition:

^ Identify the type of vibration by discussing with the customer in what speed range the vibration occurs; and whether it was apparent when the vehicle was new or whether the condition gradually or suddenly appeared.

(3) Road test the vehicle to verify the customer complaint. Please use procedure I, if necessary.

(4) Tire runout check, on-car:

^ Check wheel/tire assembly radial and lateral runouts on the car per the procedure III.
^ If runout is excessive (not ok) - Perform an off the car runout check, step (5).
^ If the runout check is ok - Go to off the car dynamic balance, step (9).

(5) Tire runout check, off-car:

^ Check wheel/tire assembly radial and lateral runouts off the car per procedure III.
^ If runout is excessive (not ok) - perform the tire to wheel match mounting procedure, step (6).
^ If the runout check is ok - Go to step (7).

(6) Tire to wheel match mounting:

^ Match mount tire to wheel per procedure IV.
^ If the runout is reduced to be within acceptable guidelines, then - Go to step (9).
^ If the runout is not reduced to be within acceptable guidelines, replace tire and/or wheel as necessary. Then - Go to step

(7) Index assembly on wheel studs:

^ Index the tire/wheel assembly on the wheel studs until the runouts are minimized.
^ If the runouts are ok - Go to step (9).
^ If the runouts are not ok - Go to step (8).

(8) Measure axle shaft and hub flange lateral runout

^ If runouts of either parts are not within specification, replace parts as necessary and then Go to step (9).

(9) Off-car dynamic balance:

^ Balance wheel/tire assembly on a two-plane off-car balancer (static one-plane off-car balancer is not recommended). For proper balancing of wheel/tire assembly, follow the equipment manufacturer's instructions.
^ If vibration condition is not corrected - Go to step (10).

(10) On-Car Finish Balance:

^ Follow procedure II for properly balancing the tire/wheel assembly on the vehicle. ^If the vibration complaint is not resolved - Go to step (11).

(11) Engine/Driveline Imbalance:

If all of the above steps are followed correctly, and the problem still persists, it is very likely that the vibration is related to engine/driveline imbalance. Check the engine/transaxle mounts, fan blades, engine accessory bolts, and brackets, and air conditioning compressor operation.