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It is the intent of this technical paper to inform tapered roller bearing producers and manufacturers of axle nuts about the results of recent research dealing with wheel bearing preload axial pressures. A testing program was conceived and perfected in the interest of correlating internal tapered roller bearing axial load pressures with the clamping forces introduced by tightening axle nut systems. Using the information presented in this technical paper, it will be possible for all manufacturers of wheel end components to develop appropriate installation instructions for their proprietary products. These instructions would be suitable for original OEM assemblies or during retrofit operations.

This technical paper continues a sequence of previous SAE Technical Papers that document progress of wheel bearing adjustment on tractor/trailer combination vehicles. In an earlier SAE paper, 2000-01-3496, misinformation provided was recognized. This material is reviewed following the conclusion of this technical paper and corrections are offered. However, of primary importance, disclosure will be made of new developments accomplished in wheel bearing preload adjustment procedures since December 2000. The intent of this paper is to advise the means by which selected amounts of preload can be introduced into trailer wheel assemblies. These are identified as axle nut adjustable systems that are serviceable by mechanics in commercial carrier fleet operations. No commentary will be presented relative to the permanent type of wheel bearing adjustment systems that are factory installed and are unable to be adjusted while in service.

This technical paper discusses the need for a retrofit program using improved technology to eliminate the use of axle nuts having the potential for failure. A review of the history of wheel end problems on highway trailers is also a portion of this presentation. Knowledge of newly perceived operational conditions will be presented along with recommendations on how they might be addressed. With review of this material, those interested in highway safety will be apprised of up-to-date information that will enable appropriate remedial action to be initiated.