Component Tests and General Diagnostics

COMPONENT TESTS - WHEELS AND TIRES

Wheel and Tire Runout

Some vehicles may exhibit a wheel and tire vibration caused by excessive runout. Runout measurements of the wheel and tire assembly can be taken both on and off the vehicle. Runout measurements can be taken both radially and laterally using a runout gauge. The runout gauge is a delicate, precision instrument and should be handled as such. The runout gauge should be mounted on a heavy solid base to eliminate gauge movement when measuring runouts. The measurements are taken using a runout gauge, which defines total runout in 64th or thousandths of an inch (depending on the brand of gauge used) and locates the high and low points of the runout.

Radial Runout









Radial runout is the egg-shaped deviation from a perfect circle and is measured perpendicular on a circumference. On a wheel and tire assembly this usually means measuring the center tire tread rib, although other tread ribs can be measured as well. The center rib is usually a solid rib, easy to measure and normally indicative of the condition of the tire as a whole. It is important to keep in mind that any rib with excessive runout can cause a concern. Total runout is the reading from the gauge. The high spot is the location of maximum runout.
1. Make sure that the tire pressures are set to the correct pressure as indicated on the vehicle certification label.

NOTE:Warm up the tires prior to taking any measurements, this will eliminate slight flat spotting. This is done during a road test.

CAUTION:Use only SST AKS551311, any time tire pressures are measured, to be sure that accurate values are obtained.

CAUTION:Place the air chuck straight on the valve stem to inflate the tire. Do not cock the air chuck during the inflation cycle. Doing so can damage the valve stem and cause air leaks.

CAUTION:Mazda Motor Corporation suggests using a round head air chuck on tire pressure sensors; it is not recommended to use air chucks with long shanks. Doing so can cause tire pressure sensor valve stem damage and loss of tire pressure.
2. Using a tire crayon, record the vehicle position on the inward sidewall of all 4 tires.

3. Remove the wheel and tire assemblies.

4. Mount the wheel and tire assembly on a suitable wheel balancer using a suitable wheel balancer

5. Position the runout gauge to take a radial measurement.

- Rotate the wheel and tire assembly to locate the low spot.
- Adjust the runout gauge to read 0.
- Rotate the wheel and tire assembly (or wheel) one complete revolution to make sure that the low spot has been found and that the runout gauge dial returns to a 0 reading.






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 not within 1.27 mm (0.050 in), locate and mark the high spot and proceed to Match Mounting Step 1 to correct the concern.
- If the runout reading of a wheel is not within 1.27 mm (0.050 in), install a new wheel.
NOTE:If there is a vast difference in measurements taken from a wheel and tire assembly checked (on the vehicle) compared to readings taken (off the vehicle), check for excessive bolt circle runout, excessive hub runout or a fitting concern between the hub and wheel.

Lateral Runout









Lateral runout is a sideways variation causing a twist or wobble and is measured on a side surface. On the wheel and tire assembly, the lateral runout measurement should be taken as close to the tread shoulder as possible. Total runout is the reading from the gauge.
1. Position the runout gauge to take a lateral measurement.

- 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 (or wheel) one complete revolution to make sure that the low spot has been found and that the dial returns to a 0 reading.






2. While slowly and constantly rotating the wheel and tire assembly (or wheel), measure the lateral runout.

- Note the variance (runout) from 0 on the dial of the gauge.
- If the runout reading of a wheel and tire assembly is not within 1.27 mm (0.050 in), locate and mark the high spot and proceed to Match Mounting Step 1 to correct the concern.
- If the runout reading of a wheel is not within 1.27 mm (0.050 in), install a new wheel.
NOTE:If there is a vast difference in measurements taken from a wheel and tire assembly checked (on the vehicle) compared to readings taken (off the vehicle), check for excessive bolt circle runout, excessive hub runout or a fitting concern between the hub and wheel.

Match Mounting









Match mounting is a technique used to reduce radial and lateral runouts 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 or by changing the position of the wheel and tire assembly on the hub.
1. Remove the wheel and tire assembly. See Service and Repair.

2. Position the wheel and tire assembly on a suitable tire machine and put a reference mark on the tire sidewall at the valve stem position.

3. Using a suitable tire machine, break the tire down from the wheel.

- Position the tire 180 degrees (half-way around) on the rim so the tire reference mark made in Step 2 is opposite the valve stem.

CAUTION:For tires equipped with a tire pressure monitoring system (TPMS), the sensor, cradle and strap can 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 can result in TPMS component damage.

4. Re-inflate the wheel and tire assembly to the specified air pressure and measure the assembly runout again. Mark the second high spot on the tire.

- If the runout is reduced to within specifications, the problem has been solved.

5. If the second runout measurement is still not within specification and both measurements are close to each other (within 101.6 mm [4 in]), the root cause is probably the tire.

- If the second high spot is not within 101.6 mm (4 in) of the first high spot, proceed to the next step.
NOTE:To make sure that the tire is causing the high runout, you must have 2 runout measurements that are not within specification and the high spots must be in approximately the same location on the tire's sidewall. In other words, the high spot followed the tire when it was repositioned 180 degrees on the wheel.









6. If the second high spot is still above specification and is 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. Install a new wheel if the wheel runout exceeds 1.27 mm (0.050 in).










7. Draw an arrow on the tire sidewall from the second high spot towards the first high spot (in the shortest direction).

- Rotate the tire 90 degrees (1/4 of a turn) in the direction of the arrow.
NOTE:If the second high spot did not follow the wheel or the tire and the runout is still not within specification, you may make improvements by rotating the tire 90 degrees (1/4 of a turn).









8. Install the wheel and tire assembly. See Service and Repair.

- Align the wheel and tire assembly using the index mark made on the wheel and wheel stud during removal.