Tire and wheel assembly vibrations are the next level of testing for low-frequency vibrations that are sensitive to vehicle speed. The tires, the wheels, the brake rotors and the wheel hubs should be systematically tested, according to the symptoms.
The following are symptoms of first-order vibrations caused by tire and wheel assemblies:
Correct the runout problem first, because the runout of a tire/wheel assembly will directly affect the amount of imbalance and radial force variation. As the amount of runout decreases, imbalance and force variation also decrease.
Important: Before measuring or attempting to correct excessive runout, carefully inspect the tire for an uneven bead seat. The distance from the edge of the ring to the concentric rim locating ring should be equal around the entire circumference. If the beads are not seated properly, remount the tire. Otherwise excessive runout and imbalance may result.
You can correct radial and lateral runout at the same time. Two methods are available for measuring runout of the tire/wheel assemblies:
Make an initial on-car visual inspection prior to performing the off-car runout tests.
Measuring the tire/wheel runout off of the vehicle is the easier method for the following reasons:
Once you have measured and corrected the runout off the vehicle, a quick examination of runout on the vehicle will indicate if any further problems exist.
If the off-vehicle measurement differs significantly from the on-vehicle measurement, the runout problem is due to one of the following:
If the vehicle has been sitting in one place for a long time, flat spots may exist at the point where the tires were resting on the ground. These flat spots will affect the runout readings. Before you take any runout measurements, eliminate these flat spots by driving the vehicle long enough to warm up the tires.
Measure the tire/wheel assembly runout as shown in the figure.
For radial runout, wrap the outer circumference with tape when you measure the radial runout. This allows for a smooth reading from the dial indicator.
Ignore any jumps or dips due to sidewall splices.
Use either of the following dial indicator sets with roller contact point J 23672 when applying this procedure:
If the runout is excessive, mark the location of the high spot and the low spot on the tire. Next, determine if the runout problem exists in the tire, the wheel, or a combination of both. Then, correct the problem. This procedure, called match-mounting or vectoring, uses the following steps:
Important: After replacing a tire or a wheel, remeasure the tire/wheel assembly runout in order to verify that the runout is within tolerance.
If you cannot bring runout within tolerance by match-mounting, dismount the tire from the wheel and measure the wheel runout of the tire. You can measure rim runout more accurately on the inside bead area of the wheel. Measure wheel runout using the same procedure as tire runout. Ignore any jumps or dips due to paint drips, chips, or welds.
Measure the radial runout of the wheel.
Measure the lateral runout of the wheel.
Measure both the inboard flange and outboard flange as shown. The tolerances for wheel runout are as follows:
If the runout of the wheel is beyond the tolerance, replace the wheel.
Important: Always measure the runout of new wheels. Do NOT assume that a new wheel is automatically good.
When replacing a wheel, refer to the wheel code that is stamped next to the valve stem. Cross-reference the letter code with the parts book.
If the runout of the wheel is within tolerance, and the tire/wheel assembly runout cannot be reduced to an acceptable level by using the match-mounting technique, replace the tire.
Important: Always remeasure the tire/wheel assembly runout after you replace the tire.
If you notice a large difference in runout measurements between on-vehicle testing and off-vehicle testing, the runout problem is due to one of the following:
The listed tolerances should serve only as a guideline. If runout measurements are within tolerance but are marginal, some sensitive vehicles may still be affected. Always reduce runout to as little as possible in order to attain optimum results under all conditions.
Radial force variation is the difference in the stiffness of a tire (1) as the tire rotates and contacts the road. The tire and wheel assemblies have some variation due to splices in the tire plies. These splices do not cause a problem unless the force variation is excessive. These stiff spots in the tire can deflect the tire and wheel assembly upward as the assembly contacts the road.
If the tire has only one stiff spot, the spot will deflect the spindle once per each revolution of the tire and wheel assembly, thus causing a first-order tire/wheel vibration. If the tire has two stiff spots, the spots cause a second-order vibration. First-order and second-order tire/wheel vibrations are the most common as a result of radial force variation. Third-order, fourth-order, or higher are possible but rarely occur.
Ensure that the tire and wheel assembly runout is at an absolute minimum. This is the most effective way to minimize the possibility of force variation as a factor in tire and wheel assembly vibrations. However, some tire and wheel assemblies exhibit vibration-causing force variation even though they are within runout and balance tolerances. These instances are becoming increasingly rare due to tighter tolerances and higher standards in manufacturing.
If you suspect force variation as a factor in tire and wheel assembly vibration complaints, substitute one or more known good tire and wheel assemblies.
You may buff the tires on a tire matching machine in order to eliminate spindle deflection. This type of equipment, not currently in widespread use, is designed to remove small amounts of rubber from the outer rows of the tread blocks at the location of the stiff spots under load. Do not use any tool that is designed to make the tire perfectly round. These tools will not correct the condition.
You may substitute one or more known good tire and wheel assemblies when a tire manufacturer is not available locally.
Lateral force variation tends to deflect the vehicle to the side, or laterally. Lateral force variation is based on the same concept as radial force variation. A snaky belt inside the tire may be the cause of lateral force. Test the vehicle with substitute tires before installing replacement tires.
A lateral force variation condition is rare. The best way to eliminate lateral force variation is to ensure that the lateral runout of the tire and wheel assemblies is at an absolute minimum.
The vehicle will wobble or waddle at slow speeds of 8-40 km/h (5-25 mph) when lateral force variation is excessive. This condition is usually related to the first-order of tire and wheel rotation.
When lateral runout occurs, inspect the wheel hub/axle flange runout if you are performing an on-vehicle test procedure, but not during off-vehicle testing. The tolerances provided are only guidelines. Perform corrections only if the on-vehicle runout cannot be brought to within tolerance.
Specification (Guideline) Runout tolerance: 0.130 mm (0.0050 in)
Use the wheel stud runout procedure whenever the following conditions occur:
Measure the stud runout as close to the flange as possible.
Specification (Guideline) Runout tolerance: 0.80 mm (0.030 in)
