Spicer Tire Pressure Control - Manual (Page 6)

system’s ability to deflate even at tempera-
tures of +65°F (18°C). Although the Spicer
System minimizes the possibility of con-
densed water in the controls and the tires,
whole water can only be controlled by posi-
tively draining all water which has condensed
from the tanks. Proper preventative mainte-
nance demands draining all tanks to zero
pressure whenever the truck is to be left
unused for an extended period.
Does a standard truck air
compressor satisfy the
requirements for TPC?
Air compressor output capacity requirements
are determined by factors such as the total
internal volume of the tires being controlled
and the pressure range over which one is
operating the tires. While in some cases a
manufacturer’s “standard” compressor may
be appropriate, it will not be in others.
Specifying too much air capacity can also be
harmful by causing additional heat which
results in oil consumption that will contami-
nate the system. Owners, dealers and manu-
facturers will need to consider the application
when specifying the compressor.
Manufacturers will also need to work with
compressor and air dryer suppliers to assure
the factory installed air system will meet the
needs of the user. Compressor and dryer
manufacturers may have established specific
installation requirements for the use of their
products with high air usage systems such as
Spicer
® Tire Pressure Control.
Is it more difficult to change tires
on a TPCS equipped truck?
Tire changes on a TPCS equipped truck will
require additional steps, which although not
difficult, will add to the amount of work
required. The technician will need to take care
and note or mark the location of the wheel
relative to the hub to assure that the new
wheel is installed in proper position to
reconnect the hoses when complete. Prior to
removing the tire, he must disconnect the air
lines and plug or cap them if the tire is still
pressurized as there are no valve cores in the
stem of a TPCS controlled wheel. (A smooth
jawed locking plier or other tool may be used
to temporarily crimp the hose). After putting
the new tire in position, the hoses must be
replaced and properly restrained to prevent
damage. While inflating, following comple-
tion of a tire change, the system may display
a “check tire” icon, indicating that air in one
tire is lower than others on the channel. This
indication should clear after the system is
used to inflate the tires.
Is the system reliable in sandy
and/or dusty environments?
The Spicer ® Tire Pressure Control System
uses many of the same operating principles
of the Spicer
® Central Tire Inflation System
which was so successful in Operation Desert
Storm. Over 5,000 systems were fielded in
that effort without any reported failures. The
desert terrain of Saudi Arabia and Kuwait
(and Iraq) represents some of the harshest
conditions in the world. The commercial sys-
tem has been tested across the United States
in wide ranging environments for over 1.5
million miles prior to production.
What is the maintenance impact of
adding a system to my truck?
Several items should be looked at from a
maintenance perspective when using vehicles
equipped with Spicer
® Tire Pressure Control.
Wheel Valve Filters – The first item is the
wheel valve filters. Filters are included in each
wheel valve in the air connection to the tire
hose. This filter traps debris from the tire and
helps to assure reliable wheel valve opera-
tion. Even tires which were clean during
mounting have been found to have loose
debris in them after many hours of operation
and it is important that this debris not get into
the wheel valve. Dana recommends that these
filters be changed whenever tires are rotated
or replaced. Since it is difficult to determine
how long it takes for this tire dirt to develop,
your application may demand more frequent
changing. Tires which deflate to uneven pres-
sures within the same axle group would be a
reason to look at changing the filters.
Non-driven Wheel End Lubrication – Another
item is the area of wheel end lubrication for
non-driven wheel ends, such as steers and
trailers. In order to deliver air to a tire, a
system must route air through the wheel end
via a rotary joint inside the hub cap. If air
were to leak from this rotary joint and pres-
surize the wheel end, the main inboard oil
seal could be damaged or displaced. The
Spicer
® Tire Pressure Control System utilizes
a special plug in the center of the hub cap
window which vents easily to make build-up
of pressure in the wheel end unlikely, and the
hub cap itself has been designed to mount
the wheel valves to provide a neat package for
steer axles.
Since the hub cap section is not uniform, the
apparent oil level in the wheel end will vary
depending on the position of the hub cap
when the vehicle is stopped. The addition of
oil to the wheel end should always be done
through the fill plug in the side of the hub
cap, not the vent plug in the window, since
the lines on the window are the appropriate
oil level only when the fill plug is at 12
o’clock. Adding lubricant to the lines with the
fill plug in any other position may result in an
over-filled condition and oil will likely leak
past the low pressure vent plug, resulting in
an unsightly leak. Furthermore, water or
detergent spray should never be directed at
the vent plug, as it can get past the plug and
enter the hub cap, contaminating the oil and
reducing wheel end life. Oil should be exam-
ined frequently for such contamination, and
be changed if any oil discoloration is found.
Many applications for Tire Pressure Control
are severe duty applications which demand
routine wheel end inspection of bearings on
an annual or semi-annual basis. You should
always follow the manufacturer’s recommen-
dations for wheel end service.
Drive Axle Wheel Ends – While the addition
of air seals into the drive axle hubs does
not create any unique requirements for
maintenance of the wheel end, it does make
adherence to current recommended mainte-
nance practices more important to assure the
best life from the seals.
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