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Limitations of use

The Tire Ball inflation system was designed and developed for use in off -road motorcycles. The system has also been proven successful in ATVs.

High temperature is the enemy of all tires. Tires inflated with Tire Balls are also prone to high temperature related failures. Simply stated sustained speeds in excess of 80 MPH are not recommended. Paved road use is not recommended above 50 MPH.

It is important that the potential user understand that excessive high temperature limitations exist when using the Tire Ball inflation system. If operating "tire surface temperatures" approach 200°F (93°C) you should be concerned about imminent Tire Ball failure.

Our understanding of heat and temperature limitations of off road tires, are based on experience. We are attempting to expand our understanding through continued research and development into "how and where" heat is generated in a tire at high speed and "what" are the important mechanisms of "how" that heat is being transferred out of the tire. If we can learn "how and where" heat is generated perhaps we can control it better and if we understand the traditional mechanisms that transfer heat out of the tire perhaps we can increase the rate at which heat is removed from a tire traveling at high speed. These are complex issues that have been studied and no doubt continue to be studied today by all the major tire companies. We hope that we can work with one or more of these companies to find a solution to high temperatures developed in tires traveling at high speed.

But until heat build up in a tire and high tire temperatures are controllable, there are heat related limitations that are a direct function of speed that must be placed on the use of the Tire Ball inflation system.

Driven (Front) Wheel
We have never seen a heat related failure on a driven (front) wheel of either a motorcycle or ATV. Never is a powerful word, there may have been failure occurrences but were never reported back to us. It is my belief that the Tire Ball system can be used in all off road applications on the front wheel, including Baja 1000 and Vegas to Reno high-speed events. These two events are the two highest sustained high speed off road events in North America. Tire Ball inflation cells have been successfully been used by top level riders in both of these events. But not without careful attention to installation and modification of the tires used to improve heat transfer.

Drive (Rear) Wheel
Heat related failures using the Tire Ball inflation system occur in heavy vehicles (650cc and up) traveling at sustained speeds (10-20 minutes at a time) in excess of 80 MPH. Paved highway use at these high speeds appear to quicken the heat rise in a tire and shorten the time to subsequent heat failure.

Tire Balls are not approved for highway use, so stay off of paved roads. If you use Tire Balls for enduro and have a transfer section that is on a paved road, stay within the legal speed limit! Additional silicone lubricant should be used in the tire carcass and on the Tire Ball cells when high-speed desert types of events are the intended use.

High ambient temperature and bright sunlight can affect the safe operating speed of Tire Ball inflated tires, but not for the reasons you would first suspect. High ambient temperature and bright "high noon" sunlight affect the heat transfer rate by reducing the temperature difference between the heat transfer media, air and terrain. Riding a bike in excess of 100 mph for long periods of time on a frozen lake bed in Northern Canada in the winter will probably not result in any heat related Tire Ball failures. The heat generated in the tire is the same as in the desert in summer but the heat transfer is more efficient because of the greater temperature difference between the tire and the air as well as the tire and the terrain surface.

Contrastingly, consider the Nevada desert in August with ambient temperatures approaching 110 degrees and surface temperatures at noon approaching 140 degrees. The temperature differences between the tire and the heat transfer media are a lot smaller so the rate of heat transfer is a lot less. The slower the heat is removed the hotter the tire can get. It is not heat that causes Tire Balls to fail, it is high temperature. To prevent failure from high temperature, the heat generation rate (vehicle speed) must be reduced. If the air is hot and the sun is shinning brightly, you need to slow down (the tire heat generation rate) to reduce the potential Tire Ball failure. If it is cloudy and cool, the heat transfer is better, so you can ride faster because the heat transfer rate is better.

Sources of heat generation in a rotating tire- a developing a theory
If you mount a wheel on a test stand such that there is no load or compression of the tire, then spin this tire at great speed, it will in all likelihood not produce any temperature rise inside the tire. However, if this tire is forced onto a surface by a load of 1000 lbs, as it is rotated, temperature of the tire will begin to increase. We can all understand that lower inflation pressure will exacerbate the temperature rise as will the speed (frequency) of rotation.

So if in this hypothetical test, we want to raise tire temperature fast, we would lower pressure and increase speed. In this hypothetical test example where would we expect the temperature rise to occur in the tire?

When rubber is deformed, heat is generated. Hysteresis (hys'ter e' sis) is the scientific term that describes the heat generated due to the time lag of the material to return to the original shape. We all know that the inflation pressure of a tire determines the amount of tire deformation and how big the contact patch is. Lower pressure means more deformation and a bigger contact patch. Lower pressure also means more heat generation in the tire.

The sidewalls flex as a segment of the tire is rotated onto the terrain surface and the weight of the vehicle (load) is applied, which results in a small amount of heat being generated in the sidewall portion of the tire.

Within the "contact patch" the tire tread has been forced to change shape from that of a three-dimensional curved surface into a more or less flat surface. This change in shape within the contact patch causes the outer surface of the tire carcass to compress while the inner surface of the carcass is stretched, which generates a small amount of heat in the tire carcass at the tread surface.

Disregarding the sidewall stiffness and its load carrying capacity for the moment, the internal tire pressure multiplied by the contact patch area exactly balance the load that is applied. Rubber in the tread portion of the tire is compressed by the load every time a specific section of tread rotates into the contact patch, which results in a small amount of heat being generated in each tread block or knob.

Tread rubber that comes in contact with a terrain surface which has a surface temperature greater than the tire surface temperature can gain a small amount of heat from the direct contact (conduction) with the terrain, which can add a small amount of heat at the surface of the knob.

Another source of heat can be direct radiation from the sun. Riding for hours in the same direction at the right time of day under the right sunlight conditions can cause tires of the vehicle to be hotter on the sunny side than on the shady side. We have all felt the higher temperatures of black pavement as well as tires exposed to sunlight than is the surrounding air.

A very important heat source to be described is that caused by motive power application. As mentioned earlier, drive wheels are the only wheels that have experienced heat related Tire Ball failures. Thus it is concluded that power application into the tire would seem to be the most important source of heat generation in tires. Power however is applied to all wheels during cornering and braking yet this power application has not been found to generate enough heat to create a high temperature failure issue, at least none we are aware of. However, power applied from the vehicle engine does appear to generate sufficient additional heat in the rear tire that the resultant high temperature can be destructive. We have all seen the leading edge wear of knobby tires associated with excessive wheel spin. This wear is the direct result of power application exceeding the traction limit of the tire and terrain.

If we could take a high-speed photograph of a knob under acceleration by a big motor on a terrain surface such as rough pavement, I would suspect it would show the knob twisted forward. This twisting is another dimension of deformation that is directly related to power application. Not only is the knob being compressed by the load applied but it is also simultaneously being twisted, i.e. deformed in two dimensions. For constant speed, the twisting deformation would be at one level and for rapid acceleration it would be at another higher level. More power (larger displacement engines) means more deformation, which results in greater heat generated. Heat generated by the application of power to the rear wheel is important, but so are all of the other sources. It is only the small additional heat produced by power application that can cause the internal temperature to exceed the tolerance capabilities of the Tire Ball cells and thus limit the frequency (speed) at which traditional heat transfer can maintain safe operating temperatures of the tire.

Rubber hardness can also be directly related to heat generated. Softer compounds will deform more than hard compounds and thus generate more heat all other conditions being equal.

If you are going to race in the desert at high-speed events, you need to use hard rubber compound tires or risk destructive high tire temperatures.

As a final consideration, for all but tubeless tires there is a frictional heat generation source that needs to be included in our tire heat generation understanding, frictional heat. Inner tube tires run hotter than tubeless tires. Relative movement of the tire and inner tube as a tire section rotates into the contact patch and frictional heat generated between the tire and tube is one explanation for this hotter running temperature. There are other contributing reasons but these get into some serious heat transfer issues.

Foam inserts (mousse tubes) and Tire Balls have a potential source of frictional heat type generation and for this reason both inflation systems are supplied with lubricants to reduce friction and lower/eliminate heat generation from this source. Improper lubricants, too little lubricant or allowing dirt into the tire can cause a serious amount of heat generated due to friction.

Dirt inside of a tire and abrasion of the inside of the tire can absorb lubricant and reduce the remaining lubricants ability to reduce frictional heating. Excessive lubricant in tires used in high speed events may help reduce the chance that dirt and dust do not soak up all of the lubricant and reduce it's function.

Use of mousse inserts or Tire Ball cells that are too small for the tire carcass will cause abnormally high deformations and frictional generated heat.

There are other external heat sources of interest such as the heat generated by brakes being conducted or convected into tires. Aircraft tires have been known to explode due high internal pressure created by brake rotor heat. These problems have been solved by greater clearances and pressure relief valves in aircraft tires, so fear not when you board the next flight.

Modifications you can make
Sanding off the outer external flash from each of the Tire Ball cells will help reduce internal tire wear. This internal wear produces rubber dust which absorbs lubricant. Once enough lubricant is absorbed internal temperature rises due to frictional heating. We can provide this sanding service if you do not have a belt sander available. 100grit or finer sand paper is recommended.

The most effective modification we have see to date is to drill holes in the tires centermost knobs and the tire carcass. Drilling 1/8" diameter holes at the base of the knobs from front to back with a specially modified drill bit heated with a propane torch has proven successful in eliminating/controlling heat failures in bikes ridden by test riders in the Vegas to Reno and Baja 1000. We are not penetrating the carcass with the drill, but only the base of the knob. The theory is to improve heat transfer by forcing air under the knob stopping any heat generated by compression and twisting of the knob from being conducted into the tire carcass. The 1/8" diameter size hole does not weaken the knob. All tires modified in this manner have survived without any "chunking off" of knobs.

If you would details of either of these modifications please contact us.