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Tire balancing

For those of you who may think that tire balancing isn't that important, consider some industry trends- they 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 they could be felt by the driver. The softer suspensions also had the same effect. The second 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. By the way, lower profile tires do provide lower rolling resistance, which helps fuel economy. 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 chances of this assembly having absolutely precise weight distribution about its radial and lateral centers are 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.

Static Imbalance:
Occurs when there is a heavy or light spot in the tire so that the tire won't roll evenly and the tire and wheel undergoes an up-and-down motion.

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.

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 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 still feel a vibration! Here are some of the other causes of vibration:
- 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 or failure - Wheel alignment is out

Balancing High Performance Tires and Wheels

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. On rare occasion, a tire may be manufactured with slightly inconsistent sidewall stiffness (creating what is called force variance) which leads to a ride problem. There is a new generation of balancers that can detect this condition and guide the technician 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 is identified for replacement.

Wheel Weight Placement

Many of today's wheel designs necessitate unique wheel weight placement to achieve both precise balance and esthetic appeal.

Your tire dealer will inform you of the best method for your wheel type.

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 wheel).

Mixed weights balance uses both clip-on and adhesive weights. The balance planes maintain the weights behind the face of the wheel.

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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