| Tire Balancing | ||
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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. |
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:
Balancing High Performance Tires and Wheels
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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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Tire Markings: A Question of Balance |
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If you are staring at paint dots on tires, you should know that they were installed to assist you in correcting tire balance and radial runout conditions.
Manufacturers of radial tires may apply a variety of colored dots on the lower sidewall for customer or factory purposes. Not all tires have markings and even the paint dots on those tires that do are temporary and can be scuffed off during normal shipping, handling and use. That's why you don't usually see them on used tires. The dots on new tires that have them are not critical but are intended to guide technicians when positioning the tire on the rim during the mounting process.  Since it is very hard to make a tire that is perfectly balanced, some tire manufacturers apply yellow dots that indicate the tire's light balance point and serve to help you balance the assembly while mounting the tire. The yellow dots should be aligned with the valve stem on both steel and aluminum wheels since this is the wheel's heavy balance point. This will help minimize the amount of weight needed to balance a tire and wheel assembly. So usually, whenever you see a yellow dot, match it up with the valve stem. This is always true except in cases where a red dot also appears in the lower sidewall. The red dot indicates the high point for both radial runout and radial force variation. As I'm sure you know, not only is it hard for tire manufacturers to make a perfectly balanced tire, it also is very difficult to make a perfectly round tire. Tires tend to have high spots and low spots. The difference between the high and the low is called radial runout. Radial runout changes the radius of the rotating assembly, causing it to raise and lower the vehicle as it rolls along. That gives the perception that the tire is "hopping" or "bouncing" down the road and ends up delivering a rough ride to the driver and irregular wear to the tread. Radial force variation is similar to radial runout and is a result of a heavy or thicker area being manufactured into the tire due to variations in component thickness, placement and overlapping. In conclusion, the yellow dot is the lightest spot and it is suggested to mount this above the valve stem. The red dot is the high point, recommended to be mounted at the low point of the rim if so marked or, preferably, per actual measurement. Please remember that these marks are just "starting" points for the tire installer to effectively mount your tires. With some of the new balancing equipment out there, the machine can do a more accurate job matching and balancing then simply relying on these dots alone. |
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| Ten Rules for Mounting and Balancing Tires Safely | ||
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1. Inspect your machines Inspect your mounting and balancing machines on a regular basis and make sure you’re performing all the maintenance that’s required. You should be looking for any obvious air leaks and that all the operating parts are working correctly, from the bead loosening system to the tool arms. The goal is to prevent surprises during operation. We tell our customers to keep all the instructions with the unit. Make sure all the decals, labels and notices are clean and visible to the operator, especially around potential pinch points. Operators should never attempt to over-ride a machine’s built-in safety features. 2. Use protective equipment Make sure operators wear safety glasses, durable clothing, steel-toed shoes and other safety gear. Anything hanging or loose-fitting should be avoided. You don’t want to get caught up in the moving parts of the equipment. Wear mechanics’ gloves, especially if you’re handling worn tires or wheels. Ear protection is important, as well. Getting into the habit of using protective equipment is a function of the shop owner’s policies. 3. Match tires to rims correctly Make it part of your standard operating procedure on every tire you service to look at the size of the new tire before mounting it. Make sure it’s the proper size for the wheel. Mismatching tires and wheels can lead to injury during inflation. With enough oomph, you can get a 16-inch tire on a 16.5-inch wheel and certainly a 16.5-inch tire will slide pretty easily onto a 16-inch rim. Always verify tire and wheel sizing. In a lot of shops, the tire tech is not the guy who’s pulling the tire from inventory. 4. Examine the wheel closely Inspect it for cracks, rust or any other damage from curbing or a pothole, which can deform the rim. Because seating can become difficult when working with a structurally compromised rim, operators may be tempted to use more air than is recommended, which can result in injury. Most manufacturers recommend 40 PSI. 5. Body positioning When mounting, techs should keep their fingers away from the bead seat area to avoid injury. The finger can be caught between the bead and the rim. Furthermore, operators should avoid positioning any part of their bodies over the tire and rim assembly during the inflation process. Use an inflation guard on the rim clamp machine. It’s almost like a little fence that the operator stands behind. 6. Don’t loosen beads before the tire has been fully deflated This causes a lot of movement against the bumper and excessive wear on the machine. You can have a blast of air that the tech isn’t expecting and that can certainly cause the wheel to jump. Don’t smoke while loosening beads either. Tires can contain flammable substances. You don’t know what will come out of that tire. 7. Don’t force the issue when mounting If you can’t seat a bead, something’s wrong. Deflate the tire completely, inspect the tire and the wheel, and re-lubricate both beads. If you take it apart and don’t find any problems and still can’t get it to seat, you need to think about contacting the manufacturers. 8. Never remove the hood on a wheel balancer. The hood is there to retain the tire should it come loose and keep things from flying off as the assembly is spinning. Also make sure the assembly doesn’t fly off the shaft. There is a wing nut that tightens the assembly on the balancer shaft. There is also have an auto-clamp option. 9. Use the right weights and apply them correctly It may seem like a minor point, but an inattentive operator can run the risk of injuring himself by pounding on incorrectly sized wheel weights. Make sure you use the appropriate weights. 10. Slow down Don’t let your machine operators skip steps in an effort to speed up the mounting and balancing process. No matter how busy your shop is, make sure they take the time to do the job correctly. When you look at the benefits of cutting corners to go faster, the saving are very minimal. These machines are designed to run properly — whatever second or two you gain, it just isn’t worth it. Five Tips for Mounting Machine Maintenance 1. Clean the machine All the tool arms — and anywhere there’s metal-to-metal joints or movement — should be cleaned with a vaporizing solvent and then lubricated with chassis grease. The table top, the clamps and all of your work surfaces should be wiped off with a vaporizing solvent once a month. 2. Look for wear and tear Inspect the clamps, looking for any worn or damaged grips. 3. Check for accuracy Check the tire pressure gauge function daily and check its accuracy monthly. The gauges in our machines are adjustable. We recommend checking the function of the pressure limiter on a weekly basis. You also want to check your oil level weekly. 4. Proper operation On a daily basis, before you get going, inspect and make sure all of your systems are operating normally. 5. Clean the screen Keep the display clean and clear. Wipe the display down with a damp cloth. You want to keep your adaptors and cones clean. Maintenance is inextricably tied to safety. It’s almost a precursor to safety. If you don’t maintain your equipment, any safety initiative you undertake will most likely be for naught. |
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If you're interested in learning more about better tire wear, see our
articles on Air Pressure,
Tire Rotation,
and Alignment. |