00-03-10-006I Information on Tire Radial Force Variation (RFV) - (Jan 28 2013) Tires - part 4
Measuring Wheel Runout and Assembly Radial Force Variation
Important:The completed worksheet at the end of this bulletin must be attached to the hard copyof the repair order.
-Measure radial force variation and radial runout.If a road force/balancing machine is used, record the radial force variation (RFV)on the worksheet at the end of this bulletin. It may be of benefit to have the lowestRFV assembly to the front left corner . If the machine is not available and the EVAdata suggests there is an issue, swap the tire and wheel assemblies from the frontto the back. Re-check on the EVA and if the problem still exists, test another vehicleto find assembliesthat do not exhibit the same frequency. If the subject vehicle exhibits vibrationin the seat, then swap only the rear assemblies and see if the problem continues.If the subject vehicle exhibits vibration in the steering wheel, swap only the frontassemblies and see if the problem continues. If the subject vehicle continues to vibrateafter swapping two assemblies then swap all four. If the vibration still exists, continuebelow.If a runout/balancing machine is used, record the radial runout of the tire/wheelassemblies on the worksheet at the end of this bulletin. If one or more of the tire/wheelassemblies are more than 0.040-in (1.02-mm), match mount the tire to the wheel toget below 0.040-in (1.02-mm). For sensitive customers, readings of 0.030-inch (0.76-mm)or less are preferable, it may also be of benefitto have the lowest runout assembly to the front left corner. If the machine is notavailable and the EVA data suggests there is an issue, swap the tire and wheel assembliesfrom the front to the back. Re-check on the EVA and if the problem still exists, testanother vehicle to find tires that do not exhibit the same frequency and swap thosetires onto the subject vehicle.After match mounting, the tire/wheel assembly must be rebalanced.
If match mounting tires to in-spec wheels produces assembly values higher than these,tire replacement may be necessary. Replacing tires at lower values will probably meangood tires are being condemned. Because tires can sometimes become temporarily flat-spotted,which will affect force variation, it is important that the vehicle be driven at least24-km (15-mi) prior to measuring. Tire pressure must also be adjusted tothe usage pressure on the vehicle's tire placard prior to measuring.
Most GM vehicles will tolerate radial force variation up to these levels. However,some vehicles are more sensitive, and may require lower levels. Also, there are othertire parameters that GM approved tire force variation measurement equipment cannotmeasure that may be a factor. In such cases, TAC should be contacted for further instructions.
Important:When mounting a GM wheel to a wheel balancer/force variation machine, always use thewheel's center pilot hole. This is the primary centering mechanism on all GM wheels;the bolt holes are secondary.