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Maintaining the tire balance on your vehicle is critical to receiving
satisfactory service from your tire investment. In addition to providing a
smooth ride, balancing is a key component in tire wear. The focus of this
article is to help you understand the balancing process and to know why it is
important to keep your tires balanced throughout their tread life.
For those of you who think that tire balancing isn't that important,
consider some industry trends that may help you rethink the issue. Perhaps the
most compelling argument for precision balancing comes from an obvious fact:
vehicles are being made lighter and lighter. The heavier cars of yesterday
actually helped smooth out the ride by dampening many vibrations before the
driver could feel them. The softer suspensions also had the same effect. Another
factor is tire technology. Generally, more responsive tires with lower profiles
(which send more road feedback to the driver) are being used in today's style-
and performance-oriented market. As a result, the slightest imbalance (as little
as half an ounce) can be felt in most modern vehicles. This is significantly
less than the average of ten years ago. For those of you who have plus-sized
your tires and wheels, balancing is even more critical.
The Balancing Act
Perhaps the best way to begin is to discuss the lack of balance. When a tire is
mounted onto the wheel, two slightly imperfect units are joined to form an
assembly weighing forty pounds (this is the average for cars). The chance of
this assembly having absolutely precise weight distribution about its radial and
lateral centers is virtually impossible. Remember that all it takes is half an
ounce of uneven weight distribution for a vibration to be felt. The illustration
below shows how an imbalance creates vibration. |
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Static imbalance: Occurs when there is a heavy or light spot in the tire that
prevents the tire from rolling evenly and causing the tire and wheel to undergo
an up-and-down motion. |
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Dynamic imbalance: Occurs when there is unequal weight on one or both sides of
the tire/wheel assembly's lateral centerline, thus creating a side-to-side
wobble or wheel shimmy. |
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The static imbalance creates a hop or vertical vibration. The dynamic imbalance
creates a side-to-side or wobbling vibration. Most assemblies have both types of
imbalance, and require dynamic balancing (commonly referred to as spin
balancing) to create even weight distribution. The balancing system directs a
technician to place counter weights on the rim's outer surface to offset the
imbalance. When the balancing system tests for virtually perfect weight
distribution, the assembly is in balance and will not vibrate. Your tires will
ride smoothly and wear evenly with regard to balance.
Keeping Your Tires Balanced
For the sake of example, assume you have driven your tires 5,000 miles since their
purchase and it's time to rotate. Over the miles, turning left and right,
hitting bumps and holes you could not see or avoid, and driving down uneven road
surfaces have led to uneven tread wear on your tires. Perhaps a pothole has
knocked-out your vehicle's alignment (this creates uneven tire wear). Well,
besides rotating the tires and getting an alignment to set things right, you
should also rebalance the tires. Even if you can't feel vibrations, they are
present. The uneven tread wear has created an imbalance that generates excessive
heat and wear on your tires. Considering the hundreds of dollars you spent on
your tires, a rebalance is a wise expenditure. If you live near one of our
stores, you should ask about the Lifetime Balancing program. For a nominal,
one-time charge you can have your tires balanced at every rotation.
Other Sources of Vibration
Very often the wheel/tire assemblies on a vehicle may be in balance but you can
still feel a vibration. Here are some of the other causes of vibration: |
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• Bent wheel
• Tire out of round (radial or lateral runout)
• Wheel-to-axle mounting error
• Inconsistent tire sidewall stiffness (force variation)
• Brake component wear or failure
• Drive train or engine component wear or failure
• Suspension wear or failure
• Wheel bearing wear of failure
• Wheel alignment is out |
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Your tire dealer can isolate many of these problems for you, and there is no
question that determining whether the tire/wheel assemblies are good and in
balance is the first place to start. However, ultimately this may not be the
source of your vibration problem.
Balancing High Performance Tires and Wheels |
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• Match Mounting
Today's high performance tires and wheels are made with
features that facilitate optimum mounting. Wheels are marked to identify the
minimum radial run-out spot (low point) on the bead seat surface. Tires are
marked with a high point location. Mounting the assembly to match these two
points is called match mounting. This method minimizes the balance weight
needed to correct any remaining imbalance and the radial run-out that may occur
in the wheel/tire assembly.
• Force Variance
On rare occasions, a tire may be manufactured with slightly
inconsistent sidewall stiffness (creating what is called force variance) which
leads to a ride problem. A new generation of balancers can detect this
condition. The balancers can also guide tire technicians to remount the tire in
an optimum position that puts the assembly within specification and eliminates
the problem. If specifications cannot be achieved, the defective tire will be
identified for replacement.
• Wheel Weight Placement
Many of today's wheel designs necessitate unique wheel
weight placement to achieve both precise balance and aesthetic appeal. Your tire
dealer will inform you of the best method for your wheel type. |
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Standard balance uses only clip-on weights as shown. This method is usually done
on original equipment steel or alloy wheels. Different type wheel weights are
used for each type of wheel. |
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Mixed weights balance uses both clip-on and adhesive weights. The balance planes
maintain the weights behind the face of the wheel. |
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The use of adhesive weights is typically reserved for chrome or other wheels
with a delicate finish. The balance planes maintain the weights behind the face
of the wheel. |
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