Caution: Failure to adhere to the following precautions before tire balancing
can result in personal injury or damage to components:
| • | Clean away any dirt or deposits from the inside of the wheels. |
| • | Remove any stones from the tread. |
| • | Use coated weights on aluminum wheels. |
Important: The tires can be balanced either on-vehicle or off-vehicle, but the
off-vehicle balancing procedures are recommended. Off-vehicle methods are
better because tire rotation will not affect the balancing. The off-vehicle
balancers are also more accurate than the on-vehicle balancers. Off-vehicle
balancers can perform dynamic balancing as well as static balancing.
Tire and wheel balancers can drift out of calibration without warning,
or can become inaccurate as a result of abuse. The balancer calibration
should be inspected every two weeks, and whenever the readings are questionable.
Tire Balancer Calibration Test
- Spin the balancer without
a wheel or any of the adapters on the shaft.
- Inspect the balancer readings.
Specification
0.00-0.25 oz
- Balance a tire and wheel assembly that is within radial and lateral
tolerances to ZERO.
- Add a 3 ounce test weight to the wheel at any location.
- Spin the tire and wheel assembly again, noting the readings.
| • | In the static and dynamic modes, the balancer should call for
3 ounces of weight, 180 degrees opposite the test weight. |
| • | In the dynamic mode only, the weight should be called for on the
flange of the wheel opposite the last weight. |
- With the assembly unbalanced to 3 ounces, cycle the balancer
5 times.
- Take the balancer readings:
Specification
Variation: 0.25 oz or less
- Index the tire and wheel assembly at four separate locations on
the balancer shaft, 90 degrees apart.
- Cycle the balancer with the assembly at each location.
- Take the balancer readings:
Specification
Variation: 0.25 oz or less
Tire Balancing Guidelines
Static and dynamic balance
are two kinds of tire/wheel balance:
| • | Static balance, also called single plane balance, affects the
distribution of weights around the wheel circumference. |
| • | Dynamic balance, or two-plane balance, affects the distribution
of weight on each side of the tire/wheel centerline. |
| • | Most off-vehicle balancers are capable of checking both types
of balance simultaneously. |
As a general rule, most vehicles are more sensitive to static imbalance
than to dynamic imbalance, with as little as 0.50-0.75 oz capable
of inducing a vibration in some vehicles. Vibration induced by static
imbalance will cause a vertical or BOUNCING motion of the tire.
Dynamic imbalance results in a side-to-side motion of the tire. This
motion is referred to as "Shimmy".
| • | Balance all four tires as close to Zero as possible. |
| • | Carefully follow the wheel balancer manufacturer's instructions
for proper mounting techniques to be used on different types of wheels. |
| • | Regard aftermarket wheels, especially those incorporating universal
lug patterns, as potential sources of runout and mounting problems. |
| • | Use the correct coated weights on aluminum wheels. |
| • | Recheck the tire and wheel assemblies for excessive runout after
they have been corrected and installed. |
| • | Evaluate the vehicle at the complaint speed and note if the vibration
has been corrected. |
| • | If the vibration is still present, or is reduced but still unacceptable,
you may find one of two possibilities: |
| - | Radial or lateral force variation |
Correcting On-Vehicle Imbalance
On-vehicle imbalance may result from components other than the tire
and wheel assemblies having imbalance. An on-vehicle high-speed balance or
replacement of suspected components may be necessary in order to correct
the condition.
Rotors do not have a set tolerance. However, rotors with more than 0.75 ounce
imbalance have the potential to cause vibration. The rotors can be inspected
for imbalance using either the on-vehicle or the off-vehicle method as
described below:
Checking Rotor Imbalance (On-Vehicle)
- Support the vehicle rear axle on a suitable hoist. Refer to
Lifting and Jacking the Vehicle
in
General Information.
- Remove the rear tire/wheel assemblies. Refer to:
| • | Wheel Removal (Cast Type - Single Front/Rear) in Tires and Wheels. |
| • | Wheel Removal (Disc Type - Single Front/Rear) in Tires and Wheels. |
| • | Wheel Removal (Disc Type - Dual/Rear) in Tires and Wheels. |
| • | Wheel Removal (Cast Type - Dual/Rear) in Tires and Wheels. |
| • | Reinstall the tire/wheel assemblies. Refer to: |
| • | Wheel Installation (Cast Type - Single Front/Rear)in Tires and Wheels. |
| • | Wheel Installation (Disc Type - Single Front/Rear)in Tires and Wheels. |
| • | Wheel Installation (Disc Type - Dual/Rear)in Tires and Wheels. |
| • | Wheel Installation (Cast Type - Dual/Rear)in Tires and Wheels. |
- Reinstall the wheel nuts in order to retain the rotors.
- Take the necessary precautions.
- Run the vehicle at the complaint speed while inspecting for vibration.
- If the vibration still exists, perform the following steps:
| 6.2. | Run the vehicle back to speed. |
- If the vibration is eliminated, perform the following steps:
| 7.1. | Remove the rotors one at a time. |
| 7.2. | Perform the vibration test for each rotor. |
| 7.3. | Replace the rotor causing the imbalance. |
| 7.4. | Inspect the balance of the new rotor. |
Checking Rotor Imbalance (Off-Vehicle)
- Measure the diameter and the width of the rotor.
- Mount the rotor on a balancer in the same manner as a wheel.
Important: The rotors can only be inspected for static imbalance. Ignore the dynamic
imbalance reading.
- Inspect for static imbalance.
On-Vehicle Balancing Procedure
The vibration problem may not be correctable with the
components removed from the vehicle. An on-vehicle high-speed balancer may
be required in order to balance the tire and wheel assemblies while still
mounted on the vehicle. On-vehicle balancing will balance the hubs and
the rotors simultaneously, and will compensate for any residual runout
encountered as a result of mounting the tire and wheel assemblies on
the vehicle as opposed to off-vehicle balancing.
Follow the on-vehicle balancer manufacturer operator's manual for specific
instructions while keeping the following tips in mind:
Balancing Tips
| • | Do not remove the off-vehicle balancing weights. The purpose of
on-vehicle balance is to FINE TUNE the assembly balance already achieved,
not to start over again. |
| • | If the on-vehicle balance calls for more than 1 ounce of
additional weight, split the weight between the inboard and outboard flanges
of the wheel, so as not to upset the dynamic balance of the assembly that
was achieved in the off-vehicle balance. |
| • | An EVA vibration sensor placed on the fender of the vehicle during
the on-vehicle balance is an excellent indicator of the amplitude of the vibration,
and the effect that the balance has on the vibration. |
| • | Evaluate the vibration after the on-vehicle balance in order to
determine if the vibration condition has been resolved. |
Radial Force Variation
Radial force variation
is the difference in the stiffness of a tire 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 (1)
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- and second-order tire/wheel vibrations
are the most common to occur as a result of radial force variation. Third-,
fourth-, or higher orders are possible but rarely occur.
The most effective way to minimize the possibility of force variation
as a factor in tire and wheel assembly vibrations is to ensure that the tire
and wheel assembly runout is at an absolute minimum. However, some tire
and wheel assemblies exhibit vibration-causing force variation even though
they are within runout and balance tolerances. These instances are becoming
rare due to tighter tolerances and higher standards in manufacturing.
The following two alternatives are available if force variation is suspected
as a factor in tire and wheel assembly vibration complaints:
| • | Substitute one or more known good tire and wheel assemblies. |
The tires may be buffed on a tire matching machine that 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. This eliminates the spindle
deflection. This type of equipment is not currently in widespread use.
Do not use a TRUER or 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
Lateral force variation
tends to deflect the vehicle sideway, 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. The tire substitution
method may have to be used before tire replacement.
A lateral force variation condition is rare. The best way to eliminate
lateral force variation as a factor in tire and wheel vibration conditions
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.
Wheel Hub/Axle Flange Runout
Inspect the wheel hub/axle flange runout when lateral runout occurs
during on-vehicle testing 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.
- Position the dial indicator
on the machined surface of the hub, the axle flange, or the rotor, outside
of the wheel studs.
- Rotate the hub in order to find the low spot.
- Set the dial indicator to zero at the low spot.
- Rotate the hub again and check the total amount of runout.
Specification (Guideline)
Runout tolerance: 0.130 mm (0.0050 in)
Wheel Stud (Stud Circle) Runout
Use the following procedure whenever the off-vehicle radial runout and
the on-vehicle radial runout are significantly different, and earlier attempts
to correct the tire and wheel vibration condition have not been successful.
- Position the dial indicator
in order to contact the wheel mounting studs.
Measure the stud runout as close to the flange as possible.
- Turn the hub to register on each of the studs.
- Zero the dial indicator on the lowest stud.
- Rotate the hub again and check the total amount of runout.
Specification (Guideline)
Runout tolerance: 0.80 mm (0.030 in)
