One of the many important decisions for fleet managers is to determine whether or not balancing your tires and wheel assemblies is worth the time and cost. There are numerous benefits to initiating a tire balancing program:
- Vehicle ride is improved, which increases driver satisfaction and comfort;
- Irregular tire wear drops significantly;
- Tire removal mile is improved;
- Fuel economy increases;
- Reduced fatigue stress of components leading to increased life of axle and wheel-end components;
- It can be the first step in solving drivers’ ride complaints.
Historically, fleets that balance their tires have primarily balanced only steer axle tires. When steer tires are out of round and bouncing down the highway, the driver will be unhappy, since the vehicle ride will not be smooth. The driver can feel the vibration coming through his steering wheel.
If improving tire removal miles while increasing fuel economy is one of your fleet’s goals, balancing trailer tires, drive tires and steer axle tires—in that order—is recommended. This is because their contribution to fuel economy and treadwear is greatest first for trailer tires, then drive tires and lastly steer tires.
There are several approved and acceptable options to balance a tire/wheel assembly. The oldest and most prevalent method to balance is to use external weights attached to the wheel rim flange. This additional weight is used to offset an unequal distribution of weight about the axis of rotation. Balancing with external weights can be done statically or dynamically. Many states have rules and regulations when it comes to using wheel weights produced from lead. There are options available in the market for lead-free wheel weights. One of the negatives associated with using external weights is that your parts department must store a large inventory of different size and type weights, and weights must be installed properly or they will come off.
A tire assembly is statically balanced when the weight is distributed equally around the perimeter of the tire and wheel assembly. The required weight is always split and placed opposite each other on the rim flanges. With dynamic balancing systems, the operator will know how much weight to put on each side and exactly at what location. Dynamic balance is more sophisticated and accurate compared to static balance. A tire/wheel assembly that is balanced statically may not be dynamically balanced; however, if the tire assembly is dynamically in balance, it will always be statically balanced.
One of the considerations of using external weights to balance a tire/wheel assembly is that the process assumes the tire will wear smoothly and evenly throughout its life—which is not always the case.
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Many fleets also use internal tire balancing materials on their tires. These materials move inside the tire as the assembly rotates down the highway. The material tends to move to the low spot of the tire assembly, which improves ride and helps reduce irregular wear. Of course, any time materials are added inside the tire assembly, it is important that they are non-corrosive and will not cause damage to the tire innerliner. Always work with your tire supplier to confirm material compatibility.
The third option to balance tire wheel assemblies is the use of balance rings. These are devices that are mounted between the brake drum/hub and the wheel. They are engineered to neutralize imbalance of the wheel end assembly as the vehicle is moving. As the wheel rotates, the balancing material and lubricant inside these balancing rings migrates to the light side. Since there are different sized rings available, always make sure you choose the proper size to avoid tire damage.
The American Trucking Associations’ TMC has developed several recommended practices when it comes to tire/wheel-end balance and reducing irregular tire wear. RP 214 is an excellent source of detailed, valuable information on the subject of tire balancing.
It should be noted that when it comes to over the highway tires 20 in. and larger, the maximum balance weight allowed is 15 ounces for steer tires and 19 ounces for drive and trailer tires. Tires that are running in on/off highway service are allowed a maximum weight of 17 ounces on steer tires and 21 ounces on drive and trailer tires. For those fleets who are running wide base tires, such as the 445/50R22.5, steer tires are allowed 22 ounces of balance weights and 26 ounces for drive and trailer tires.