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.
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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.
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.
Occurs when there is unequal weight on one or both sides of the tire/wheel assembly’s lateral center line, 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 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:
- Bent wheel
- Tire out of round (radial or lateral run out)
- 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
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
* 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.
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* 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. 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.
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.