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Improved Clamp Force Technology

Only HiSpec builds The Safety Wheel.

Superior engineering and innovation is the driving force behind HiSpec and The Safety Wheel. This directory showcases why HiSpec wheels are specially designed for the RV and trailer industries. Reliability and safety–there is a HiSpec difference.

Just look for the wheels with the blue HiSpec Wheel logo.

“Look for Wheels with the Blue HiSpec Wheel Logo”

As part of the “Safety Wheel” concept, ICF TechnologyTM provides the following benefits:

  • ICF™ makes your first torque your last and keeps your wheels secure.
  • When properly installed, ICF™ creates a bulletproof joint between the HiSpec aluminum wheel and the mounting hub.
  • Re-torque is not necessary with ICF™ technology.
  • ICF™ adds the highest level of safety to your wheel and tire program.

Wheel separation, a situation where the tire/wheel assembly detaches from the vehicle, inevitably causes damage to the vehicle, and more importantly creates a dangerous situation for motorists.

Improved Clamp Force Technology™ from HiSpec Wheel takes a giant step towards eliminating this issue and improving user safety.

In 2002, numerous recalls and wheel separation events prompted National Highway and Transportation Safety Administration (NHTSA) involvement to discover the root cause of wheel offs. One major cause was attributed to excessive paint on the wheel hub. The proposed solution was to eliminate paint from the mating surface of the hub; yet wheel separation continued to be an issue.

Further testing revealed that the wheel/hub joint must maintain the proper clamp load “In Service” to avoid a separation. Clamp load is defined as the sum of the tension loads generated in each of the studs when the lug nuts are tightened. Adequate clamp load relative to the weight (GVW) of the trailer is critical. Clamp load combined with the friction at the hub-wheel interface keeps the wheels on the vehicle.

How does ICF™ work?

ICF™ data from both laboratory and on-road testing shows radical reductions in the stud-to-stud clamp load variation. In any joint where there are multiple fasteners (5 to 8 studs for most wheels) each fastener generates a unique clamp load. Despite applying equal torque to each lug nut, the resultant clamp load in each stud is different. Through minimizing variation stud to stud, the net clamp load (the sum of all the clamp loads in the joint) is maximized increasing the average clamp load across the joint while maintaining safe levels relative to the capacity of each stud.

ICF Technology™ minimizes this variation and as a result, when properly installed, the joint is bulletproof and re-torque is not necessary.

How was this done?

The details are proprietary, but HiSpec Wheel addressed three areas:

  1. Revisions to the wheel/hub interface (the mating surfaces between the wheel and the hub.)
  2. Revisions to the steel insert – only HiSpec Wheel products have these revisions – other wheels without ICF™ do not have the same technology either with or without a steel insert.
  3. A high level of attention to detail and quality control.

Why is this important?

Trailer capacities are expressed as Gross Vehicle Weight (GVW), the maximum allowable weight of the trailer and cargo together. This load is easily measured with scales when the trailer is sitting on its wheels and is known as Static Load.

The GVW condition is referred to as a 1G load.

Dynamic loads are measured as a multiple of the static load and are produced when the trailer is in motion and encounters surface irregularities such as potholes. These events create loads higher than the 1G load that was measured statically. The magnitude of the dynamic load is dependent upon the type of event the vehicle encounters and also the type of suspension. Typically, peak vertical loads for a tandem leaf spring trailer with equalizer will be in the 3.3G range, while a rubber torsion tandem axle trailer will see about 5.9Gs on the same peak events.

For a tandem leaf spring axle on a typical durability schedule without peak events, this comes out to a required clamp load of about 2,500 pounds per stud, while for a rubber torsion tandem axle suspension with peak events, the requirement for a 6 lug application comes to about 6,200 pounds per stud. These are the minimum clamp loads necessary to retain the wheels in all conditions.

Clamp load relaxation must also be considered. In wheel/hub joints, most of this loss occurs in the first 5 minutes after tightening and is due to creep of the bearing surfaces that come into contact when the lug nut is tightened. On the road, further creep of the mating surface occurs and is called “dynamic clamp load relaxation.”

The bottom line is that  HiSpec developed ICF™ to improve the net clamp load in the joint and increase safety on all events that trailer wheels may encounter. That’s why it is called the Safety Wheel.

How does this compare?

Some competitors’ wheels, when torqued to 120 ft-pounds, will generate about 4,400 pounds of clamp load. When the statistical minimum clamp load values are calculated and the average static clamp load relaxation figures are subtracted, the results are a net clamp load of 2,100 pounds (dark blue line). This value is below the minimum 2,500 pound required for the least aggressive condition and shows that in some cases there will not be adequate clamp load to retain the wheel/tire assembly under ideal conditions. This is exactly the combination that caused recalls in 2002 and the reason the Safety Wheel was invented!

More importantly, you can see that ICF™ technology easily exceeds the maximum requirements of 6,200 pounds. The key to this data is the consistency of clamp force retention. The average is around 9,000 pounds, which easily exceeds the 6,200 pound maximum requirement.

It is important to note that all aluminum wheels are not created equally. Only those with ICF™ technology will produce these results, and only HiSpec has the Safety Wheel.