The Brake Shop: Wear Wars
Brake Shop
Old mounting hardware,
installation mistakes or even
misguided choices can all
lead to premature brake wear
By John G. Smith, info@wordsmithmedia.ca
B
rake components are referred
to as wear items for a good
reason. It is only a matter of
time before everything from
linings to gray iron will be sacrificed in
the name of controlled stops.
The challenge is when these parts
wear more quickly than expected.
Shops often are baffled when one
set of components seems to be replaced
more frequently than another, especially when the differences are observed
between virtually identical trucks. When
that happens, says Randy Petresh, vicepresident of technical services at Haldex,
it is time to dig through the data.
After all, the challenges can be linked
to a number of issues as diverse as vehicle uses, product choices and installation procedures.
Premature wear often can be
traced to something as simple as a
change in how the truck is being used,
Petresh explains.
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“Maybe the vehicle now is being
used in a different location, different
routes, different contracts, and consequently the duty cycles have increased,”
he says. Those who begin hauling different trailers may suddenly be causing
the tractor to provide more than its fair
share of the stopping power.
Identical trucks can have a very
different experience in different
areas of the country, agrees Tom
Runels, Bendix-Spicer’s engineering
manager for drum brakes. One vehicle might travel flat and even routes,
while the other is traveling through
the mountains or simply needs to
make more repeated stops. “It comes
down to trying to match systems for
their duty cycles.”
Even though over-the-road tractors
typically have enjoyed long brake life,
advances in the name of fuel economy
are presenting challenges of their own,
he adds.
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Aerodynamic truck profiles are being combined with tires that offer lower
rolling resistance, and the skirts under
a trailer further reduce drag. These
advancements all require the brakes to
deliver more force with every stop.
Ultimately, every component choice
also needs to balance stopping requirements with other performance issues,
such as the control of vibrations, noise
or heat. Parcel delivery trucks or school
buses running suburban areas, for example, likely will need to be quieter than
their on-highway counterparts.
Given the lack of standards governing brake material sold in the aftermarket, one of the easiest ways to avoid
differences in performance is to match
the existing components as closely as
possible.
There will be some challenges if a
standard 130-lb., 16.5x7 brake drum
is replaced with an option that weighs
about 100 lbs., observes Johnathan