00-03-10-006I Information on Tire Radial Force Variation (RFV) - (Jan 28 2013) Tires
|Subject:||Information on Tire Radial Force Variation (RFV)|
|Models:||2013 and Prior GM Passenger Cars and Light Duty Trucks|
This bulletin is being revised to reinforce the importance of performing a wheel centeringcheck on wheel balancers so equipped. Please discard Corporate Bulletin Number 00-03-10-006H(Section 03 – Suspension).
Important:Before measuring tires on GM approved tire force variation measurement equipment,the vehicle MUST be driven a minimum of 24-km (15-mi) to ensure removal of any flat-spotting.Refer to the latest version of Corporate Bulletin Number-03-03-10-007: Tire/WheelCharacteristics of GM Original Equipment Tires.GM approved tire force variation measurement equipment MUST be calibrated prior tomeasuring tire/wheel assemblies for each vehicle.
Note:If the equipment being used is capable of performing a centering check, the centeringcheck must be completed before taking measurements of balance or RFV.
The purpose of this bulletin is to provide guidance to GM dealers when using GM approvedtire force variation measurement equipment. This type of equipment can be a valuabletool in diagnosing vehicle ride concerns. The most common ride concern involving tireradial force variation is highway speed (105-115-km/h (65-70-mph) shake on smoothroads.
Tire related smooth road highway speed shake can be caused by three conditions: imbalance,out of round and tire force variation. These three conditions are not necessarilyrelated. All three conditions must be addressed.
Imbalance is normally addressed first, because it is the simpler of the three to correct.Off-vehicle, two plane dynamic wheel balancers are readily available and can accuratelycorrect imbalance. Balancer calibration and maintenance, proper attachment of thewheel to the balancer, and proper balance weights, are all factors required for aquality balance. However, a perfectly balanced tire/wheel assembly can still be “ovalshaped” andcause a vibration.
Before balancing, perform the following procedures.Tire and Wheel DiagnosisSet the tire pressure to the placard values.With the vehicle raised, ensure the wheels are centered on the hub by loosening allwheel nuts and hand-tightening all nuts first by hand while shaking the wheel, thentorque to specifications using a torque wrench, NOT a torque stick.Visually inspect the tires and the wheels. Inspect for evidence of the following conditionsand correct as necessary:Missing balance weightsBent rim flangeIrregular tire wearIncomplete bead seatingTire irregularities (including pressure settings)Mud/ice build-up in wheelStones in the tire treadRemove any aftermarket wheels and/or tires and restore vehicle to original conditionprior to diagnosing a smooth road shake condition.Road test the vehicle using the Electronic Vibration Analyzer (EVA) essential tool.Drive within posted speed limits at 105-115-km/h (65-70-mph) for a sufficient distanceon a known, smooth road surface to duplicate the condition. Determine if the vehicleis sensitive to brake apply.