Each wheel nut should be re-torqued as part of routine maintenance. A necessary procedure that ensures each nut is secure. This would be sufficient in preventing wheel failure but problems can still develop and go undetected. Wheel separation incidents are estimated to be in the many thousands a year and most go unreported if there is no damage or insurance claim to be made.
Wheel nut indicators enable the operator to conduct faster and more frequent routine safety checks. Without indicators, it's not possible to see if a nut is loose without physically checking it. With indicators you can be confident that nothing has moved by simply looking at each wheel. This saves valuable time and makes it easier for drivers to detect and fix problems before they become dangerous.
Loss of clamping force through both under torquing and over torquing can lead to wheel failure. Years of regular maintenance creates long term wear but bad practises and incorrect calibration of tools can accelerate this process. Over torquing stretches the stud beyond its tensile limit where it can no longer maintain the required clamping force. Under these conditions, the stud will eventually shear, placing the remaining fasteners under increased load. Undetected this can result in a progressive failure and the wheel is no longer secured.
Out of Sight Out of Mind
Although locking nuts together seems like a good idea, there are situations where loss of clamping force can still occur and locking devices will not be effective. The assumption that nuts are "securely locked" also encourages lazy maintenance practices while providing zero feedback to the operator. A nut that keeps coming loose, is an indication that clamping force is not being adequately maintained. Without this critical feedback, a locking device masks these early warning symptoms, effectively blinding you from potential underlying problems as they develop. If not regularly checked, these devices will only inhibit the drivers ability to detect, fix or report the problem to the service department.
Causes of Wheel Separation
• Over torquing
• Under torquing
• Stud is damaged or lost its tensile strength
• Thread is dirty, damaged or corroded
• Mating surfaces are obstructed - wheel not seated properly
• Differential thermal expansion and contraction
• Incorrectly tightened or overlooked nut sequence
• False torque readings - equipment calibration
IMPORTANT - Hexchex® only assist routine safety inspections and DO NOT replace proper maintenance. We take no responsibility for incorrect use or any failure as a result of poor wheel maintenance.