Component Tests and General Diagnostics
Wheels And Tires
Component Tests
Radial Runout
Radial runout is the egg-shaped deviation from a perfect circle and is measured perpendicular to the circumference. On a wheel and tire assembly, this means measuring the center tire tread rib. The center rib is indicative of the condition of the tire as a whole. Total runout is the difference between the maximum-to-minimum gauge reading. The high spot is the location of maximum runout.
Loaded Runout Measurement (Hunter Road Force(R) 9700 Series Wheel Balancer)
NOTE: Diagnosis of tire/wheel vibration should not be performed on tires with less than 320 km (200 mi). Some initial tire/wheel vibration issues (such as flat spotting) correct themselves after the tires have been in service for 320 km (200 mi).
This procedure is intended to assist with the diagnosis of wheel and tire assembly runout and/or force variation issues.
The Hunter Road Force(R) 9700 Series Wheel Balancer measures the wheel and tire assembly's loaded runout and the tire's radial spring rate. The balancer then converts the runout into pounds of force (termed as Road Force(R)). Measuring loaded runout (Road Force(R)) is more effective than measuring unloaded runout using a dial indicator.
1. Using a tire crayon, record the vehicle position on the inner sidewall of all 4 tires.
2. Remove the wheel and tire assemblies. For additional information, refer to Wheel and Tire .
3. NOTE: Use only the Digital Tire Pressure Gauge any time tire pressures are measured to be sure that accurate values are obtained.
Make sure the tire pressures are set to the correct pressure as indicated on the Vehicle Certification (VC) label.
4. NOTICE: Make sure the correct wheel balancer adapters are used when mounting the assembly to the wheel balancer or damage to the wheel may occur.
NOTE: Make sure the wheel and tire assembly is clean and free of foreign material prior to installation on the balancer.
NOTE: The wheel balancer inflation station must be turned OFF for tires with inflation pressures of 414 kPa (60 psi) or above.
Mount the wheel and tire assembly on a suitable wheel balancer using the correct wheel balancer adapters as shown. Refer to the list of recommended wheel balancer adapters on the PTS website.
5. Measure the Road Force(R).
- Temporarily mark the high spot and the Road Force(R) value on the sidewall of the tire. If the wheel and tire assembly Road Force(R) value is not within specification, carry out the Match Mounting procedure to optimize the wheel and tire assembly.
- If the wheel and tire assembly Road Force(R) value is within specification, permanently mark the high spot and the Road Force(R) value on the inward sidewall of the tire for reference during future wheel and tire service. Balance the assembly and install the wheel and tire on the vehicle using the Wheel-to-Hub Optimization procedure.
Runout Measurement (Dial Indicator)
NOTE: Diagnosis of tire/wheel vibration should not be performed on tires with less than 320 km (200 mi). Some initial tire/wheel vibration issues (such as flat spotting) correct themselves after the tires have been in service for 320 km (200 mi).
NOTE: Loaded runout measurements are the preferred method for verifying tire serviceability. While a dial indicator can be used to optimize the position of the tire on the wheel, the unloaded runout measurement cannot accurately determine if the tire should be removed from service.
Use the following procedures if normal diagnostics leads to a potential runout issue.
Some vehicles may exhibit a wheel and tire vibration caused by excessive runout. Radial runout measurements can be taken using a dial indicator and should be measured with the wheel and tire assembly mounted on a suitable wheel balancer. Make sure the dial indicator is mounted securely to eliminate gauge movement when measuring runout.
1. NOTE: Use only the Digital Tire Pressure Gauge any time tire pressures are measured to be sure that accurate values are obtained.
Make sure the tire pressures are set to the correct pressure as indicated on the VC label.
2. Using a tire crayon, record the vehicle position on the inner sidewall of all 4 tires.
3. Remove the wheel and tire assemblies. Refer to Wheel and Tire .
4. NOTICE: Make sure the correct wheel balancer adapters are used when mounting the assembly to the wheel balancer or damage to the wheel may occur.
NOTE: Make sure the wheel and tire assembly is clean and free of foreign material prior to installation on the balancer.
Mount the wheel and tire assembly on a suitable wheel balancer using the correct wheel balancer adapters as shown. Refer to the list of recommended wheel balancer adapters on the PTS website.
5. NOTE: Apply masking tape on the center tread rib to allow for a smoother measuring surface. Some fluctuation of the gauge reading is expected. Observe the overall sweep of the gauge from the highest to the lowest spot on the tire.
Position the dial indicator and stand with the dial indicator on the center tread rib.
- Rotate the wheel and tire assembly (or wheel) to locate the low spot.
- Adjust the runout gauge to read 0.
- Rotate the wheel and tire assembly one complete revolution to make sure the low spot has been found and the dial indicator returns to 0.
6. While slowly and constantly rotating the wheel and tire assembly (or wheel), measure the radial runout.
- Note the variance (runout) from 0 on the dial of the gauge.
- If the runout reading of a wheel and tire assembly is greater than 1.14 mm (0.045 in), locate and temporarily mark the high spot and runout reading on the sidewall of the tire and carry out the Match Mounting procedure to optimize the wheel and tire assembly.
- If the runout reading of a wheel and tire assembly is 1.14 mm (0.045 in) or less, permanently mark the high spot and the runout reading on the inner sidewall of the tire for reference during future wheel and tire service. Balance the assembly and install the wheel and tire on the vehicle using the Wheel-to-Hub Optimization procedure.
Match Mounting
NOTE: Road Force(R) values in illustrations are shown in pounds.
Match mounting is a technique used to reduce radial runout or Road Force(R) on wheel and tire assemblies. Excessive runout is a source of ride quality complaints and match mounting can be used to minimize the runout. Match mounting can be accomplished by changing the position of the tire on the wheel.
1. Position the wheel and tire assembly on a tire machine and put a reference mark on the tire sidewall at the valve stem position.
2. NOTICE: For tires equipped with a Tire Pressure Monitoring System (TPMS), the sensor may be damaged by incorrect tire mounting or dismounting. Dismount the tire from the wheel as instructed in the Disassembly and Assembly procedure. Failure to follow these instructions may result in component damage.
NOTE: Always make sure that the final high spot and measurement values are permanently marked on the inner sidewall of the tire for reference during future wheel and tire service.
Using a suitable tire machine, separate the tire beads from the wheel.
- Lubricate the tire beads using a suitable fast drying, corrosion inhibiting tire bead lubricant.
- Position the tire 180 degrees (halfway around) on the rim so the valve stem reference mark is opposite the valve stem.
3. Reinflate the wheel and tire assembly to the specified air pressure and measure the assembly again using the dial indicator or Hunter Road Force(R) 9700 Series Wheel Balancer. Mark the second high spot on the tire.
- If the runout or Road Force(R) is reduced to within specifications, the concern has been resolved. Balance the assembly and install on the vehicle using the Wheel-to-Hub Optimization procedure.
4. If the second runout or Road Force(R) measurement is still not within specification and both high spots are close to each other (within 101.6 mm [4 in]), the root cause is probably the tire (the high spot followed the tire).
- To be sure the tire is causing the high runout, it is necessary to have 2 runout or Road Force(R) measurements that are not within specification and the high spots must be in approximately the same location on the tire's sidewall. If the tire is the cause, install a new tire, balance the assembly and install on the vehicle using the Wheel-to-Hub Optimization procedure.
- If the second high spot is not within 101.6 mm (4 in) of the first high spot, proceed to the next step.
5. If the second high spot is still above specification and within 101.6 mm (4 in) of being opposite the first high spot on the wheel, the root cause is probably the wheel (the high spot followed the wheel). Dismount the tire from the wheel, mount the wheel on a balancer and check the wheel runout. If the wheel runout exceeds 1.14 mm (0.045 in), install a new wheel, balance the assembly and install on the vehicle using the Wheel-to-Hub Optimization procedure.
6. NOTE: If the second high spot did not follow the wheel or the tire and the runout is still not within specification, improvements may be made by rotating the tire 90 degrees (one-fourth turn).
Draw an arrow on the tire sidewall from the second high spot towards the first high spot (in the shortest direction).
- Separate the tire beads from the wheel and rotate the tire 90 degrees (one-fourth turn) in the direction of the arrow.
Wheel-to-Hub Optimization
Wheel-to-hub optimization is important. Use the clearance between the wheel and hub to offset or neutralize the Road Force(R) or runout of the wheel and tire assembly. For every 0.001 inch of wheel-to-hub clearance, the Road Force(R) can be affected between 1 and 3 pounds depending on the tire stiffness.
NOTE: The example below illustrates how the clearance between the wheel and the hub can be used to offset the high spot of radial runout or Road Force(R). Following the procedure will make sure of the best optimization.
1. Position the wheel and tire assembly on the vehicle so the high spot location is at the 6 o'clock position and install the wheel nuts by hand until snug.
2. NOTE: Do not allow the full weight of the vehicle to rest on the tires while tightening the wheel nuts.
Lower the vehicle until the tires make contact with the ground, slightly loading the suspension. Tighten the wheel nuts as described.