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Coupled Forces


Why using less weight is not a shortcut

In our July issue on page 26, the article titled “Less Weight, Great Balance” (or at www.brakeandfrontend.com) answered a lot of questions, but it also brought up some new ones. The article was on the new technology that many new balancers are featuring that can reduce the amount of weight a tire balancer uses.

The technology comes at a time when lead weights could be phased out in the next two years. Replacement weights will be more costly for shops. Also, when was the last time you were able to increase your prices for balancing?


But, the technology is showing that a better balance can be achieved with less weight. The technology works by giving the balancer software that can analysis wheel forces and rationalize the weight placement in a manner that older balancers could not. Here are two questions purposed be a few of our readers.

”What is the difference between forces and the associated correction weight used to balance?”

Keep in mind that as a force remains constant, the correction weight size must change as a new correction weight location is chosen. The correction weights must become larger or smaller as the distances, widths and diameters of the weight locations change. A good analogy is like having to pull on a short wrench harder to loosen a nut because it is shorter than a socket with a long ‘breaker’ bar. Flangeless wheel designs are proliferating. Many modern allow wheels have rim flanges no longer used for correction weight, thus creating smaller distances apart from each weight. Smaller distances between weights can dramatically increase the amount of weight required when making the ‘couple’ balancing correction. Also, today’s tire sizes and assembly weight vary dramatically and are also heavier, which further increases the amount of balance weight required.


It’s interesting to point out that tire and wheel static force (shake) is greatly affected by small amounts of change in correction weight. The couple force (wobble), is NOT greatly affected by small amounts of change in correction weights. In fact, unlike static force correction, large amounts of correction weight must be used to make small changes in couple force.

“Why has computer wheel balancing changed now….after doing it the same way for almost 30 years?”

Unlike wheels and tires commonly used during the 1970s and 1980s (when electronic balancers were introduced), today’s tire sizes and assembly weights vary dramatically and are now heavier which increases the amount of balance weight required. Furthermore, flangeless wheel designs are proliferating. Rim flange locations are often no longer used for the clip-on correction weight.


Using tape-on weight creates smaller distances apart from each weight which dramatically increases the amount of weight when making ‘couple’ balancing corrections. The new feature and software takes this into account. The proliferation of designs now reveals that balancing in the old way wastes time and money. Its not that the old way is wrong … it’s just not necessary to do it the sane old way wasting time and money. Today’s computers, if engineered well, use their processing power to accomplish benefits which used to be unattainable before the computer existed.

If you’re in the market for a new wheel balancer, you should look into this. You will find that your shop operators actually prefer its new “ease of use” and the fact that there have actually been steps removed to simplify the balancing process. Your operators will also be doing a better job without knowing it. Procedures that were used by some to short-cut, bypass or waste time have also been removed.

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