Fleet Maintenance - 36

Though the information gathered
through TPMS is extremely beneficial,
the downside is that someone still needs
to step in and make the fix.
"TPMS is valuable to a certain
customer who wants the awareness
while also maintaining the control of
doing the maintenance themselves,"
says Lee Alexander, category director,
ITMS, for Stemco, a manufacturer of
heavy duty components and solutions
for the commercial vehicle market.
"These fleets that use TPMS usually
have their own maintenance facilities
and aren't driving long, remote routes
where they could get stranded."
In general, TPMS tends to be less often
specified than ATIS among commercial
vehicles. Much of this comes from the
convenience ATIS provides by automatically inflating or releasing air when
tires fall above or below the specified
levels of inflation. Part of this preference may stem from previous challenges with TPMS products.
"Early TPMS products failed to satisfy fleet requirements since they only
delivered alerts to drivers, who usually
ignored them and were initially plagued
with sensor problems that resulted in a
distrust of these systems," Fisher says.
Problems also occurred with TPMS
sensors involving either the signal,
battery life, or maintenance.
"There are two primary types of
sensors - internal sensors mounted
to the wheel inside the tire and valve
stem cap sensors," says Steve Miller, vice
president of engineering at Pressure
Systems International (PSI), a provider
of automatic tire inflation systems for
commercial vehicles.
Internal sensors can be problematic
because they can get lost during tire
replacements and may also increase
the need to remove the tire from the
vehicle when a sensor battery is low.
However, this type of sensor is theftand damage-resistant, whereas valve
stem cap sensors are not. Cap sensors
also require removal from the valve
stem in order to add air to the tire,
which creates an inconvenience whenever access to the inner tire is necessary.
It is estimated that around 60 to 70
percent of fleets use ATIS over TPMS,
notes Howard Fromm, senior product
manager at Meritor, a manufacturer of
automobile components for military
suppliers, trucks, and trailers.
"ATIS is more commonly specified to
trailers because [trailers] are typically
stored and pooled in yards around North
America - in much higher numbers
than tractors - where there is no access
to maintenance," Alexander says.
With little access to maintenance,
having a tire management system like
ATIS can help keep a fleet running with
as little downtime as possible.

36 Fleet Maintenance | October 2019

When it comes to specifying ATIS on
the drive and steer tires, the technology
isn't quite as advanced.
"Drive axles present significant
design challenges in routing the air
through the drive axles and through
the wheel-end," Miller explains. Product
development is ongoing, and not yet
ready for the commercial vehicle
market. "Hub-mounted systems exist
but require the vehicle to be in motion
before delivering air to an underpressurized tire, so one must drive on an
underinflated tire, which is what you
are trying to avoid in the first place."
There are additional challenges
with the specification of ATIS on steer
axle tires, Miller notes. Routing the air
through the steering knuckle as well as
potentially damaging exposure of the
airlines on steer axle wheels are issues
still in need of solutions. But it is likely
these steer axle issues will not be fixed
until a remedy is found for the challenges with drive axle tires.
Although ATIS is the preferred
system for many fleets compared to
TPMS, it also has its drawbacks. When
the ignition is turned off, or the trailer is not connected to the tractor, the
system stops working, meaning if a
tire is damaged it has the potential to
go flat. Also, continually having air
pumped into a leaking tire is not good
for the tire. This may result in tread
separation. Additionally, the use of
ATIS introduces the potential for leaks
in the tire management system itself if
not properly maintained, which could
lead to system failure.
Each system has its pros and its cons,
but "you'll never completely avoid maintenance or downtime," Alexander says.
"These systems are designed to make
it more manageable and predictable."

Communicating issues

Communication between the tire
monitoring and management systems,
and the driver and fleet, vary greatly
depending on whether the fleet uses
TPMS or ATIS.
With ATIS, an indicator light is
mounted on the front driver's side
portion of the trailer where it can be
seen in the driver's side-view mirror.
When the light is illuminated, the
system is engaged, and air is flowing
through to the tires. If fleets wanted
not only the driver, but also the shop,
to know when this is happening, they
can use a telematics system to connect
the power circuit to this indicator light.
When a trailer is first connected to a
tractor, ATIS will run for a few minutes
to charge up the system and fill any tires
that may have lost pressure. It should be
noted, if the light comes on again during
vehicle operation, there is likely a leak,

The do's and don'ts of
checking tire pressure
Recommended best practices for avoiding
underinflation and overinflation in tires.
When it comes to tire inflation, having tires over- or undeinflated could spell trouble for a fleet. Tires must have just
the right amount of flex. Too much pressure makes the tires
more susceptible to being punctured, and too little pressure
causes heat buildup and internal structural damage. Either
way, no good comes from the wrong amount of pressure.
"Tire condition should be inspected on a regular basis," says Phil
Mosier, manager of commercial tire development for Cooper Tire.
Cooper Tire specializes in the design, manufacture, marketing, and sale of passenger car,
light truck, medium truck, motorcycle, and
racing tires. "And, daily pre-trip and posttrip inflation pressures should be taken."
Regardless of whether or not a fleet
uses TPMS, fleets should still have
recommended practices for manually checking tire pressure. This
ensures the monitoring system, if
specified, is operating accurately.
Furthermore, know when to check
the tire pressure. While a vehicle is in
operation, it is common for the tires to
increase in pressure due to heat, therefore checking the tire pressure should not
be done while the vehicle is in oper» Cooper Tire's PRO Series
ation or within about three hours
LHS steer tire features
of tire rest time. The optimal times
Energy Conservation
to check the tire pressure is in the
Optimization (ECO)
morning or when the tire is cold.

technology that combines tire
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Photo courtesy of Cooper Tire

As far as maintaining tire pressure goes, Mosier says, "The two
main ingredients to this maintenance are time and diligence."
Having everyone within the organization on board with performing
scheduled and routine maintenance checks is the best way to
ensure all tractors and trailers
have the proper inflation pressure
according to a fleet's specifications.

Keeping tires at the proper level of inflation means
more miles on those tires before they wear out.
"The more miles a tire runs means lower operating costs for the
fleet," Mosier explains. "Whether over- or underinflated, the tire's
footprint or contact patch will cause the tire to wear fast and/or create irregular wear which causes the tire to be removed prematurely."
To keep tires in optimal working condition, here is Mosier's
list of do's and don'ts for checking tire pressure:
Do:
* Use a quality air pressure gauge
* Check pressures often on all tires
* Match inflation pressure to the loads expected to be carried
Don't:
* Decrease pressures until the tires have had
at least three hours to cool down
* Assume the tires need to be inflated to the maximum inflation listed on the sidewall

Fleet Maintenance

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