A total vehicle alignment
program is an essential part of any Fleet manager’s or owner
operator’s maintenance plan. Improper tractor-trailer alignment and
tire inflation can affect handling, stability, suspension component
life, ride characteristics, tire wear and even decrease fuel economy.
Attention only to the tractor may not give all the cost savings and
benefits anticipated. This article focuses on trailer alignment and
i effec on a Fleet’s operating cos.
Two major expenditures for any
Fleet or owner operator are tires and fuel. To optimise tread wear and
fuel economy, trailer axles should maintain proper alignment along
with tractor axles. A misaligned tractor can impact trailer tire life
just as a misaligned trailer can impact tractor tire life. Due to
technological improvements, the radical tire las longer than ever
before. Trailer tires tend to show more uneven or irregular wear than
steer or drive tires. This is because trailer tires are free rolling
and do not get the surface scrubbing action that removes initial
irregular wear, like the power scrubbing of the drive tires or the
turn scrubbing of steer tires. Due to reduced scrubbing, irregular
wear patterns on trailer tires grow even more pronounced over time.
A
trailer traveling down the road slightly sideways is not necessarily
a good indicator of alignment issues that impact tire
wear. A trailer tracking slightly to the curb could have
perfect alignment to the kingpin, but be thrown off due to road crown
creating a sideways thrust due to gravity. Operators who want their
trailer to track straight behind the tractor on crowned roads may need
a bias the trailer axle alignment establishing a positioning that
counteracts the thrust of gravity from the slope of the road. This
bias alignment will not significantly impact tire wear as long as axle
parallelism is maintained. According to tire experts, for optimised
trailer tire life, maintaining parallelism between tandem axles of 1/8
inch or less is the most important factor aside from proper tire
inflation. Toe is another important factor in optimising tire life
(Figure 1). Steer axles have an adjustable toe setting while trailer
axles have a manufactured setting that is not adjustable in the field.
Major axle manufacturers suggest that a neutral toe setting is optimal
for extending trailer tire life.
Pulling a trailer with
misaligned axles not only forces the driver to oversteer, but also
creates the potential of uneven wear on all trailer tires. Uneven tire
wear has become a major concern for most maintenance managers.
Replacing twelve trailer tires could cost between $3,000 and $4,500
for the trailer owners. Certain types of tire wear are indicators of
possible trailer misalignment. Check alignment when these signs
appear:
- random erratic wear around the tire circumference
- excessive wear on one side of the tire
- rib depression wear or punch wear (one or more of the inner
ribs worn below the adjacent rib around the tire)
By inspecting tires at regular
intervals and adjusting alignment when signs of alignment-induced tire
wear first appears, operators will extend their tire life and optimise
fuel economy.
Other factors that affect
tread life are within the operators control. Over-inflating tires by
20 psi can decrease tread life by 17 percent, and speed changes from
105kph to 120kph can change wear rate by two percent. Speed changes
and weight can also affect fuel economy. The accepted industry rule is
that for every 2kph over 90kph, fuel economy goes down by .04Lpk.
Running 120kph verses 90kph can cost 20 percent of kilometre
expectations. Speed can also shorten tire life. The higher the speed,
the more heat the tire casing generates. Under-inflating tires also
generates excess heat due to increased flexing. Heat degrades the tire
casing, promoting irregular wear that in turn shortens tread and
casing life. Clearly, there are many guide forces influencing proper
tire care and maintenance. If a suspension hanger is bent or broken or
if major components need to be replaced, a more extensive realignment
will be necessary. Trailer axle alignment can be made fairly simple,
unlike a tractor alignment which involves various angles of steer axle
geometry, caster, camber and toe. Trailers equipped with quick
alignment systems can be aligned easily by moving one or both ends of
the axle forward or backward until tandem axles are parallel and axles
are positioned perpendicular to the chassis centerline. A properly
aligned trailer will result in improved tire mileage, optimised fuel
efficiency, better handling and lower operating cos.
|
The
Hendrickson Advantage
|
By specifying a Hendrickson
air-ride suspension, Fleet managers and owner operators take the first
step in controlling their operating cos. Immediately they benefit
from Hendickson’s lightweight suspensions which will help maximise
payload and add to fuel efficiency. Hendrickson suspensions are
designed with minimum wear items and a durable pivot connection to
make axle realignment virtually unnecessary under normal operating
conditions.
Hendrickson is the third
largest trailer axle manufacturer in North America. By finish
machining both spindles on the axle in a single operation and
controlling the suspension attachment, we are able to produce a
superior, neutral-toe axle and suspension assembly. Neutral toe
promotes truer rolling trailer tires kph after kph. Truer rolling
equate to less drag and friction, which results in improved fuel
economy and promotes even tire wear.
Hendrickson’s QUIK-ALIGN
simplifies axle alignment. QUIK-ALIGN offers a fast and easy method to
adjust and set trailer alignment by using two flanged collars that are
inserted into slots on each side of the frame bracket. The outboard
flanged collar is eccentric with a half-inch square opening to insert
a breaker bar or ratchet.
By
rotating the eccentric collar clockwise or counter-clockwise, the
suspension’s axle is moved fore or aft. The maximum range of
adjustment is +/- 45 degrees from 12 o’clock positioning. If more
adjustment is needed, the other end of the axle may also be adjusted.
Once the alignment is adjusted, pre-tighten the shear-type bolt and
recheck your measurements before fully torquing the pivot connection.
Other factors for
successful trailer alignment include proper tools and correct trailer
positioning. For additional information on Hendrickson’s QUIK-ALIGN
pivot connection hardware and recommended alignment procedures, refer
to the following Hendrickson publications:
• B103- QUIK-ALIGN Bushing Pivot Connection
• B99- QUIK-ALIGN Fasteners
• L579- Alignment Procedures
Hendrickson’s lightweight
suspensions and neutral-toe axles supply the Fleet owner and owner
operator with the tools needed to control operating costs, and QUIK-ALIGN
supplies a quick and easy way to align trailer axles.
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