Vibration at 35-40 MPH

This PI has been revised to add the Buick Allure. Please discard PIC3882.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Vehicles may exhibit a vibration concern at 35 - 40 MPH. Electronic vibration analyzer (EVA) hertz readings may indicate a first or second order tire vibration and the EVA amplitude (G force) readings may indicate that there is room for improvement.

.10 or higher = there is a definite concern and diagnosis and repair are required. As an example, a .10 G vibration feels similar to how a vehicle might feel if a tire/wheel had an excessive amount of runout or was 1 or 2 ounces out of balance. The amount of improvement available is substantial.

.05 to .07 consistently = a vibration of a marginal nature. The opportunity for improvement exists, but any improvement, which is gained, will be moderate. Road conditions may also cause this type of reading and the dealership may need to drive the vehicle on a different road surface to see if the reading/feel changes.

.03 to .07 fluctuating = a vibration of a marginal nature/possibly acceptable, or one which may be the result of road surface variation on a given stretch of road. More caution should be exercised prior to proceeding with repairs. The customer's vehicle should be compared to stock units, if available. If further action is taken, the emphasis should be on diagnostics and parts replacement should be held to a minimum. The reading needs to be compared to "seat of the pants" feel and in a few instances, a third party such as an AVM may need to drive the vehicle to evaluate if further action is warranted.

.03 or less consistently = not likely to be a customer concern which can be addressed through the repairs made to the vehicle. Caution should be used prior to any consideration given for repairs. The vehicle needs to be compared to stock units. It is possible that repairs will prove ineffective. Any improvement, which is available, would be minimal at best.

Note: In some instances involving vibrations the EVA may not always detect the severity of the complaint. In those instances, "seat of the pants" feel needs to be compared to the readings. If the two tests conflict each other, then the diagnostics in this PI need to be applied and the required readings obtained (runouts, radial force variation readings, results of match mounting etc.) so it can be understood if an incremental improvement can be made.

If the EVA readings indicate that there is room for improvement continue with the following procedure:

1. Visually inspect the tires and the wheels. Inspect for evidence of the following conditions and correct as necessary:

-	Missing balance weights

-	Bent rim flange

-	Irregular tire wear

-	Incomplete bead seating

-	Tire irregularities

-	Mud/ice build-up in wheel

-	Stones in the tire tread

2. Check the radial force variation (RFV) of all the wheel/tire assemblies. The wheel/tire assemblies need to have 12lbs or less of RFV.
3. Match mount wheel/tire assemblies over 12lbs of RFV. If the wheel/tire assembly still has over 12lbs of RFV after match mounting then the tire will have to be replaced.
4. Check the RFV of the new tire and verify that it has 12lbs or less of RFV. If the new tire has more than 12lbs of RFV it must also be replaced. The dealer may have to try multiple replacement tires to achieve the radial force variation specification. It may even be necessary to resort to another tire brand.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.