Reducing Speed to Improve Fuel Economy vs Balancing All Axle Ends

Some truck fleets are now reducing their highway operating speeds as low as 59 mph to improve fuel economy and they are reporting substantial improvements in fuel efficiency.

One of the main reasons for fuel efficiency improvement in reducing speed has come about because the speed of 59 mph is below the resonating rpm of the wheel assemblies, and 62 mph is just borderline of the resonating frequency of the suspension.

 What is the resonating frequency of the suspension?

It is the speed where the RPM of the wheel assembly is at the same frequency as the rebound frequency of the spring suspension. For example 600 rpm and 600 rebound per minute (10 Hz); at this speed the rpm of the wheel assembly out of balance portion couples with the rebound frequency of the suspension.

The effect of the coupling of these two separate frequencies multiplies the out-of-balance portion of the wheel assembly that was already multiplied through centrifugal force, to a force strong enough to lift up on the axle at every revolution. This force is felt as a vibration throughout the vehicle. This action causes an increase in rolling resistance due to the extra flexing of the tire tread on the road surface, and also sidewall flexing at every revolution.

The end result here is that it takes extra fuel power to rotate these out-of-balance wheel assemblies at the resonating speeds that are above 59 mph to 62 mph, depending on tire size or circumference.

Is the vehicle safety effected by out of balance wheel assemblies?

  “A study at the Pennsylvania Transportation Institute makes use of a circular track developed by R. R. Hegmon. This track has been modified so that roughness of a known amplitude and wavelength can be inserted in a wheel track. Testing was reported at TRB (13) and showed a 30% loss of traction between 8 and 12 Hz.”¹ 

Also the circumference of 18 wheels tires just happen to be the same as the distance between washboard roads hops that are all cause by axle hops at the same frequency.

Are we to believe that all these circumstances are just coincidence or are they all related and part of the same problem; out of balance wheel assemblies?

Why all tires and wheel assemblies should be balanced.

When assembling all parts of a wheel assembly there is an acceptable tolerance for imperfections, and believing they will end up balanced is farfetched, especially considering that all these parts have to be centered perfectly to the pivoting point of the axle. Remember that the best tires in the world are still only one of five parts that make up the wheel assembly.

Another advantage of balancing all complete wheel assemblies besides fuel economy improvement is that the tires run cooler and last considerably longer; 25 to 50% is regularly reported. 

Truck owners do have an option if reducing speed is not one.

Instead of reducing speed they could balance their tires and complete assembly (the axle end) with a balancing method that has proven to improve fuel economy in a TMC and SAE type ll test. Auburn University ran this test for Counteract Balancing Beads. The test was run to verify and confirm fuel economy improvements being reported by long haul users of this product in all wheel positions, these reports ranged from 5.5 to 9% improvements.  The Auburn Test was very similar to a short haul operation of 20 miles one way, stop and turn around, then pick up speed again and return. This Auburn University test resulted in a 2.2% reduction in fuel consumption. The reason for the difference in reported findings and the Auburn university test is there is no savings while picking up speed by balanced tires and complete wheel assemblies or by reducing vehicle speeds. The savings are only at highway speed at the resonating frequency.

It should be noted for anybody wanting to improve fuel economy by balancing all complete wheel assemblies (the axle end), that so far only one product and technology has been able to prove a fuel economy improvement. Other products have tried and failed to prove any savings. These products might claim to be the same and look alike, but they are not. Counteract Balancing Beads applies one more patented science and technology to their product that makes it perform like fixed weight balancing of the complete wheel assembly while remaining automatically self-adjusting.

The advantage of this extra patented technology is that the tire and wheel assemblies do not go out-of-balance at every stop or turn, or while engaging curves on the highway in comparison to other inertia balancing methods. In evidence of this a tire heat buildup test has been conducted by comparing a free flowing competitive inertia balancing product to Counteract Balancing Beads. This test was conducted by a Brazilian Federal University; the result showed that tires balanced with Counteract balancing Beads ran a remarkable 60ºF degrees cooler than the competitive product. This is very important, as heat is the number one enemy of tires; it reduces tread and casing life and is also the number one cause of tire separations and tire failures.

If you are wondering why all truck tires are still not being balanced, here are some the reasons;

It was believed that because of the heavy weight carried by these truck axles, tires did not have to be balanced, just the steering tires are being balanced; then you have to ask why if that is true?

There is more of such false belief about balancing; for example; “We buy the best tires the world so we don’t need balancing”. Again the tire is only one part of those wheel assemblies, so why then are company drivers paying out of their own pockets to get steering tires balanced to get a decent ride?

The real reason for not balancing was that it used to be impossible to balance all wheel assemblies on trucks and trailers. Only half of the wheel assemblies could be balanced, the tire and the rim, and this could make it worse than not balancing at all. Before the tubeless radial all truck fleets ran tube type bias tires mostly on spoke wheels. The amount of flat tires repaired on the road was at least twenty times greater than the tires and wheels being used today. This also made it impossible to keep tires balanced. The practice of not balancing was accepted for these reasons, and continued down the line as an accepted practice until today.

More fleets have and are taking our advice and some are reporting up to 9% fuel savings, and tire life increases of up to 50%. If you find these reports incredible, we have them in writing from very respectable members of the trucking industry. The cost of balancing all wheel assemblies with this proven trouble technology is only a small fraction of the savings.

These test results and testimonials on these reports are available on our website: www.counteractbalancing.com

¹ “Influence of Roadway Surface Discontinuities on Safety”, Transportation Research Circular E-C134 May 2009. pg 18