Wheels - Balancing Tips and Procedures
GROUP 36Wheels and Tires
Bulletin Number
36 02 88 (1627)
Montvale, NJ
June 1988
Technical Dept.
SUBJECT:
Balancing of Wheel and Tire Assemblies
MODELS:
All
Situation:
With state-of-the-art tire and wheel technology, the need to follow proper procedures when balancing wheels and tires as well as using the appropriate equipment has become critical. If proper balancing procedures are not followed, a less then first class quality balancing job will be done, which can lead to comebacks and cause a detrimental effect on customer satisfaction as well as reducing the workshop's productivity.
Attempts to take shortcuts to save time in dealing with a wheel/tire imbalance will often cause the job to take longer because everything has to be done over.
Procedure:
1. Check tire pressure of all four wheels and correct if necessary.
2. Warm the tire by driving the car for a sufficient distance at speeds that will thoroughly warm the tread.
Note:
State-of-the-art tires are more prone to "flat spotting" than previous, technology tires.
As a precaution against "flat spotting", immediately raise the car up so that all four tires are off the ground. If the vehicle is allowed to rest on the tires even for a short period, "flat spots" can develop in the tires, which will give false readings when attempting to balance.
3. Check general condition of wheels and tires. Look for physical damage to tread or sidewalls, general condition of tread, or unusual wear patterns. Visually check for physical damage to wheels. Replace as necessary.
4. Check to see if the tire is completely seated on the rim by visually inspecting the ribs on the sidewall in relation to the rim. If the tire is not fully seated, it should be dismounted, and the bead should be visually checked for damage. If not damaged, coat the bead liberally with a tire mounting lubricant, and remount.
CAUTION:
NEVER USE SILICONE SPRAY TO LUBRICATE THE BEAD.
5. Mount the tire and wheel assembly on the wheel balancer using the proper centering bushing. DO NOT USE A CENTERING CONE! (See S.I. 04 03 87 (1335) for further information). Spin the assembly and visually check for radial and lateral runout. If there is any suspicion of excessive runout, the lateral and radial runout of the wheel and the wheel/tire assembly must be checked.
Use a runout gauge (P/N 88 88 6 361 000) to check the lateral and radial runout of the tire and wheel assembly. Radial runout should be checked at both shoulders of the tread as well as the center of the tread. Lateral runout should be checked in an area where sidewall lettering will not affect the readings.
If the runout of the assembly is beyond specifications (refer to current Technical Data fiche), mark the position of the valve and dismount the tire. Check the radial and lateral runout of the wheel in the bead seating area. If the wheel is within specifications, lubricate the tire bead with a tire mounting lubricant and remount the tire, turning it 900 from its original mounted position. Re-check the assembly for runout and, if necessary, rotate the tire another 900 on the rim. If the runout of the assembly cannot be brought into specifications by rotating the tire, the tire must be replaced.
6. Mount the tire/wheel assembly on the balancer using the proper centering bushing. If the balancer has a horizontal shaft, mount the wheel with the valve stem at the bottom.
Balance the assembly according to the balancer manufacturer's instructions, using the chart for correcting any remaining imbalance after the initial weights are installed.
7. After the assembly has been balanced, remove from the balancer and remount on the car. If the balancer used is of the horizontal shaft type the wheel should be mounted on the car with the valve stem pointed down. This compensates for any play between the wheel and the hub by ensuring that any slack is always in the same position and eliminating the possibility of movement of the slack to a different relative position.
If a wheel lock is used, it should be located opposite the valve stem. Torque the wheel studs as specified.
8. In order to compensate for any imbalance in the hubs or brake rotors, on the car finish balancing is required. Finish balancing is the only way to ensure that all residual imbalance is removed from the tire and wheel assembly as it runs on the vehicle.
When setting up the finish balancer, the surface used must be hard, firm and level. All doors and deck lids must be completely closed and no one should be in or leaning on the vehicle (exception being the E-30).
Once again, use the attached chart as a guide for weight changes or movement when removing any remaining imbalance with an off-the-car finish balancer.
Special Hint:
If a customer should wish to have the BMW alloy wheels chromeplated, the plating shop should not polish the bead seating surface of the rim. Polishing the bead seating surface will reduce the friction coefficient between rim and tire, thereby allowing micro-motion of the tire on the rim and eventually creating an imbalance situation.
For more information, review the VIS program "Tire and Wheel Balancing" and S.I. 36 02 79 (395) "Diagnosis and Handling of Tire/Wheel and Related Vibration Complaints".