december2022 - 9

The good news is that fleets that keep up to
date with the latest braking technology, as well as
related preventive maintenance and inspections,
shouldn't lose any sleep over brake issues. And
to ensure your rest, we've put together a comprehensive
look at the current brakes on the market,
along with some tips on how to avoid downtime
caused by out-of-service violations and prevent
or mitigate collisions.
Before getting into that, let's revisit the proper
braking standards for stopping. As a key element
of safety, commercial vehicle stopping distances
are codified in law. Specifically, FMVSS (Federal
Motor Vehicle Safety Standard) 121 calls for air
brake systems to fully stop tractor-trailers in
no more than 250 ft. when loaded to their gross
vehicle weight rating (GVWR) at 60 mph. This is
true for commercial vehicles using either air disc
brakes or S-cam drum brakes.
Drum or disc? Fleets weigh in
So which type of brake can better help you meet
these FMVSS standards?
According to Bendix Commercial Vehicle
Systems, a 6x4 tractor-trailer going 60 mph takes
200 ft. to stop with air disc brakes and 225 ft. with
drum brakes. An independent test of Bendix
ADB22X air disc brakes completed on a test track
by Pitt Ohio revealed that at 55 mph, these ADBs
stopped 15 ft. earlier than drums.
" Fifteen feet is the length of a car, " noted Jeff
Mercadante, VP of safety at Pitt Ohio, a perennial
fleet safety award winner. " When you get up to 70
mph, you're talking closer to 50 to 60 ft. "
Drum brakes, though, make up the majority
of systems in trucking, as they initially cost less.
ADBs, however, have gained market share in the
last decade. In 2015, ADB adoption was about 15%,
while in 2020 it doubled to 30%. ADBs have fewer
parts for quicker servicing, which can lead to higher
uptime and a better total cost of ownership. But
that hardly settles the debate.
Terrance Wall, senior manager of maintenance
technical support at Ryder, pointed out that for
decades, S-cam type drum brake systems have
been the " go-to " standard for medium- and
heavy-duty trucks and tractors.
" Drum brakes are a consistent economical
solution that provides common components
across multiple vehicle platforms as well as
weight classes, " he said. " And since the implementation
of reduced stopping distance regulations
in 2013, drum brake lining manufacturers
have improved materials to meet or exceed the
stopping distance requirements. "
" Although air disc brakes do have a slightly
shorter stopping distance, drum brakes still easily
meet the requirements, " Wall continued. " Air disc
brake systems do have an advantage when brakes
heat up and brake fade becomes more evident,
but with a multi-vocational fleet, a uniform and
economical option becomes the primary focus
second only to safety. "
For Ryder, that is where drum brake systems
have an advantage. When operating a wide variety
of vehicles and with multiple repair locations,
standard practices that include uniform training,
tooling, and maintenance procedures are paramount
to maximizing the useful life of brake
components while maintaining the safety and
cost effectiveness of the brake system.
Penske Truck Leasing, meanwhile, mostly specs
ADBs. " To capitalize on their full benefit, however,
both the tractor and trailer need to be equipped
with air disc brakes, " noted Chris Hough, Penske's
VP of maintenance, design, and engineering.
Air disc brakes benefit the Penske fleet in several
ways. In the area of safety, Hough noted, they
provide shorter stopping distances and reduced
brake fade. From a maintenance standpoint,
there are fewer moving parts and grease points,
and no need to measure brake stroke. Also, pad
replacements are a relatively quick and simple
process. Penske shops also are stocked with brake
vendor-specific tools, along with hub handlers and
various gauges to measure the remaining brake
pad life and to inspect the rotor condition.
Hough also pointed out that ADBs have helped
reduce the number of units placed out of service
for brake stroke compliance issues during roadside
inspections. " When it comes to ROI, there
are some segments that are hard to measure, " he
explained. " In general, we have found that ADBs
provide a lower brake maintenance [cost per mile],
provide our customers with improved stopping
distances, and increase uptime. "
The advent of new technologies such as lane
departure, electronic stability, and adaptive
cruise control, which are now being integrated
with ABS systems, also contribute a great deal to
extending the life of foundation brake systems, he
added. ADB systems also offer electronic pad wear
sensors, which can provide data via telematics to
assist in PM interval planning and procedures.
" All brake component manufacturers provide
specific maintenance procedures to ensure
optimal performance and life from these
components, " Hough said. " By integrating
these procedures into your brake maintenance
program, coupled with the utilization of the
correct tools, the maximum useful life at the
most economical cost can be realized. "
" ADB systems provide benefits such as less time
required to replace lining material and fewer
components to lubricate, " Hough continued.
" However, even with these benefits, ADB systems
typically cost more to maintain and are difficult to
standardize across a multi-vocational fleet without
maintaining a larger inventory to accommodate
the different spec and lining requirements. "
For example, some operations with repeated
stop-and-go applications, such as refuse and inner
city routes with multiple deliveries, can realize
cost savings from shorter maintenance times and
extended pad life when ADB systems are equipped
with the proper friction material.
However, he cautioned that the ease of getting
an accurate measurement of the lining material on
both the front and rear of the rotor is consistently
a drawback on currently designed ADB systems.
This, in turn, typically leads to less than full utilization
of the lining material if the pads are being
changed prematurely.
" It is important to carefully analyze the duty
cycle and operation of the fleet to determine
the optimal type of brake system that makes
economic sense but also provides the maximum
Brake tools
in the shop
According to Kevin Pfost, coordinator,
technical service at Bendix
Commercial Vehicle Systems, these
are the shop tools and equipment
needed to properly maintain and
repair air disc and drum brakes:
* Friction wear gauges
* Tape measures and micrometers
* Magnetic base and dial indicators
* Borescopes and inspection mirrors
* Disc brake hub and rotor jacks
* Drum dollies
* Torque wrenches
Additionally, he recommends that
fleets and service providers use
manufacturer training as well as
reference Service Data Sheets
and troubleshooting guides.
Product innovations also impact
how brake system service and
repairs are performed, related
Denisse Pedraza at Haldex. " Haldex
offers a complete toolbox with all
required items for air disc brake
service, " she explained. " Our toolbox
is standard; the only unique tool
necessary to remove ModulT pads
is a Torx 55-bit for making brake
adjustments, which is included. "
Shop tools and equipment for
properly maintaining and repairing
brakes is something to discuss
with brake suppliers, noted Chuck
Brodie at ZF. " With our MAXXUS
L2.0 system, you can replace brake
pads with basic tools, but ZF also
has tool kits for deeper maintenance
such as guide pin bushing replacements, "
he said. " For ABS, you need
our diagnostic software, TOOLBOX
Plus, to go with your basic toolset. "
useful life while retaining maintenance efficiency
for your technicians, " Hough stated.
Avoiding OOS violations
No matter what types of brakes are employed
by a fleet-and it may even be a mix of both on
the same tractor-trailer-the driver and maintenance
team must keep a close eye on their systems
because the Commercial Vehicle Safety Alliance
(CVSA) will be watching.
Unfortunately, not all fleets do. In the 2022
CVSA International Roadcheck commercial
motor vehicle inspection and enforcement initiative,
brake system issues resulted in the largest
percentage of violations: 25.2% in the U.S., Canada,
and Mexico combined. In fact, brakes were the top
reason for out-of-service violations in both the U.S.
December 2022 | FleetMaintenance.com
9
http://www.FleetMaintenance.com
december2022

Table of Contents for the Digital Edition of december2022
