GUEST EDITORIAL
Wheel end bearing adjustment is often
viewed as an isolated task that will only determine
if the bearings will wear reasonably well
and not fail prematurely. However, the procedures
used, and the fi nal settings that result,
have a big impact on the effi ciency and cost
of maintenance as well as every
facet of the wheel end performance
of tractors and trailers.
Endplay or no endplay
Th e majority of Class 8 wheel ends are referred
to as conventional wheel ends, or manually
adjusted wheel ends. Technicians use torque
wrenches to turn a spindle nut and apply
torque force to the nut, which then applies an
unknown amount of load force to the bearings.
Th e last steps call for a “turn back” of the spindle
nut, which can leave bearings “loose” in an
endplay setting. A dial indicator is supposed
to be used to measure how much endplay is in
each and every wheel end aft er it is adjusted.
Alternative wheel end systems, referred to
as “pre-adjusted,” can result in bearings set
62 Fleet Maintenance | November/December 2017
to endplay and cannot be further adjusted to
improved settings.
Endplay bearing settings compromise
bearing and wheel end performance. Bearing
manufacturers state the best bearing life
occurs when all endplay is removed, and bearings
are set to light preload.
Th e Society of Automotive Engineers (SAE)
published Surface Vehicle Recommended
Practice J2535 as a guide that shows optimum
life at preload settings ranging from 250 to 500
ft -lbs for steer axles and 500 to 1,000 ft -lbs for
drive and trailer axles.
Innovations over the last 10 years now
enable fl eets to remove all endplay from their
wheel ends, set the bearings to the SAE light
preload settings and enjoy all the benefi ts of
better performing wheel ends.
Consistency, speed
and accuracy
Th ere are three key aspects for maintenance
managers to consider with their wheel end
bearing adjustment process:
Consistency: By their nature, torque wrench
procedures can be very diffi cult to control. It
is nearly impossible to maintain consistent
practices from technician to technician, and
from shop to shop. Even with frequent wheel
end training, torque wrench procedures leave
a lot of room for each technician to create their
own process. Maintenance managers express
great frustration with this lack of consistency,
because they know it results in costly wheel
end performance issues.
Speed: Maintenance organizations are
constantly reviewing their operations for
effi ciency improvements so they can invest
their technicians’ time wisely. Current torque
wrench procedures are slow and cumbersome,
and consume too much valuable technician
time to achieve poor results.
Accuracy: For some time now, the recommended
endplay settings for wheel bearings is
0.001” to 0.005” of looseness. Most fi eld engineers
confi rm wheel end bearings to be in a
range from 0.003” to over 0.010”. Just a small
twitch of the torque wrench during the “turn
back” step certainly can change the setting.
The benefits of
eliminating endplay
Engineers and technical experts agree optimal
wheel end performance and safety can
be achieved when all endplay is eliminated,
and the bearings are set to light preload.
Improved bearing life
Without endplay, bearings last longer because
more of the tapered rollers share the vehicle
load. When loose, the load is not well distributed
and can cause premature wear and other
issues within the bearings.
Reduced seal failures
Loose bearing settings directly impact seal
function, and will lead to wear and tear, and
quick premature failure.
Fleets that remove endplay from their bearings
report seal failures have been eliminated.
Th is translates to reduced maintenance costs,
reduced warranty claims and a decrease in
technician labor time handling seal failures.
Lower tire program costs
Most fl eets suff er from some degree of
uneven tire wear, leading to low tire removal
mileage. Causes of low tire mileage, sometimes
severe, may include alignment problems, poor
tire balancing, under-or over-infl ation and
service duty of the vehicles.
Improper bearing adjustment is almost never
mentioned by maintenance staff as a cause of
uneven tire wear and premature tire removal.
Yet, fl eet maintenance managers who implement
a program to eliminate endplay from
wheel ends report a rise in their tire removal
mileage. Th is translates directly to lower tire
program costs.
In addition, other wheel end problems,
including brake system performance, ABS
faults, steering vibration and overall ride
quality all can be caused by loose wheel end
bearings.
Maintenance managers who experience one
or more of the wheel end performance problems
listed above should consider the possibility
their bearing adjustment procedures may
be the culprit.
Addressing wheel end
performance problems
Wheel end bearing adjustment procedures can have a big
impact on wheel end performance and maintenance costs.
By John E. Rode
CHIEF EXECUTIVE OFFICER, TEMPER CORPORATION
The company (www.tempercorp.com) has been engineering
solutions and manufacturing bearing adjustment
products for industrial and commercial vehicle
bearing assemblies since 1969. Rode founded Temper
Axle Products Corporation in 2006 to make and distribute
Doctor Preload bearing adjustment tools and
Temper-Loc spindle nuts. Rode is a mechanical engineer
and is the inventor of record on more than 100 U.S. and
foreign patents
» A technician removes all bearing endplay
and sets to preload with precision.
Photo courtesy of Temper Axle Products Corporation
» 900 Series
Doctor Preload
bearing adjustment
tool for tapered
trailer spindles
Photo courtesy of Temper
Axle Products Corporation
/www.tempercorp.com