Fleet Maintenance - 23

»»With reductions in stopping distance, easier
and faster maintenance procedures, fewer
replacements with longer pad service life and
rotor service life, and flexibility in terms of
their specification, it is clear why fleets have
continued to adopt air disc braking systems.
iStock

[ BRAKES ]

T

he industry has been witnessing a trend with
the increased adoption of specifying air disc
brakes (ADBs). Specification of air disc brakes
on heavy duty commercial vehicles gained
momentum in the U.S. after the Federal Motor
Vehicle Safety Standard (FMVSS) No. 121 for air
braking systems enforced a reduction in heavy
duty commercial vehicle stopping distances,
with required compliance as early as 2011. The
increased adoption rate of ADBs can be attributed to these changes, since ADBs aid in stopping
a vehicle in a shorter distance than traditional
drum brakes. The rate and extent of ADB use has
been growing ever since.
Some fleets are specifying ADBs on all axles
while others are specifying ADB/drum brake
combinations. Whatever the case may be, fleets
should be aware of the benefits ADBs can provide,
service and maintenance considerations with
these brakes, and the decisions to be made when
specifying ADBs.

Differences in components
and mechanics
ADBs and drum brakes both apply torque to slow
the vehicle. They both take inputted air pressure
applied within a brake actuator or brake chamber
to translate a linear force to apply the brakes. The
similarities, however, stop there.
Drum brakes take the linear force from the
chamber to the slack adjuster to help maintain
running clearance. The S-cam is turned to apply
force against the drum shoe friction pads, which
are pushed against the inner surface of the rotating drum. This process creates the torque to help
slow the vehicle.
 Continued Page 24

»»Air disc brakes, such as this one from
Bendix, provide less fade, easier maintenance,
weight reduction, and have dramatically
improved stopping distances.
Photo courtesy of Bendix Spicer Foundation Brake

August 2019 | VehicleServicePros.com

23


http://www.VehicleServicePros.com

Fleet Maintenance

Table of Contents for the Digital Edition of Fleet Maintenance

Uptime: Is assessing cost-per-mile enough?
Do you know your TCO?
Vehicles: How to ensure optimum air system performance
In the Bay: The ABCs of ADBs
Shop Operations: The importance of managing fluid dispensing in the shop
Training: Invest in the future
Diagnostics: All scan tools are not created equal
Management: Are you good at PM?
Fleet Parts & Components
Tools & Equipment
Guest Editorial: Cold weather solutions for fleets
Fleet Maintenance - 1
Fleet Maintenance - 2
Fleet Maintenance - 3
Fleet Maintenance - 4
Fleet Maintenance - 5
Fleet Maintenance - 6
Fleet Maintenance - 7
Fleet Maintenance - Uptime: Is assessing cost-per-mile enough?
Fleet Maintenance - 9
Fleet Maintenance - Do you know your TCO?
Fleet Maintenance - 11
Fleet Maintenance - 12
Fleet Maintenance - 13
Fleet Maintenance - 14
Fleet Maintenance - 15
Fleet Maintenance - 16
Fleet Maintenance - 17
Fleet Maintenance - Vehicles: How to ensure optimum air system performance
Fleet Maintenance - 19
Fleet Maintenance - 20
Fleet Maintenance - 21
Fleet Maintenance - In the Bay: The ABCs of ADBs
Fleet Maintenance - 23
Fleet Maintenance - 24
Fleet Maintenance - 25
Fleet Maintenance - 26
Fleet Maintenance - 27
Fleet Maintenance - Shop Operations: The importance of managing fluid dispensing in the shop
Fleet Maintenance - 29
Fleet Maintenance - 30
Fleet Maintenance - 31
Fleet Maintenance - 32
Fleet Maintenance - 33
Fleet Maintenance - Training: Invest in the future
Fleet Maintenance - 35
Fleet Maintenance - Diagnostics: All scan tools are not created equal
Fleet Maintenance - 37
Fleet Maintenance - Management: Are you good at PM?
Fleet Maintenance - Fleet Parts & Components
Fleet Maintenance - 40
Fleet Maintenance - 41
Fleet Maintenance - Tools & Equipment
Fleet Maintenance - 43
Fleet Maintenance - 44
Fleet Maintenance - 45
Fleet Maintenance - 46
Fleet Maintenance - 47
Fleet Maintenance - 48
Fleet Maintenance - 49
Fleet Maintenance - Guest Editorial: Cold weather solutions for fleets
Fleet Maintenance - 51
Fleet Maintenance - 52
Fleet Maintenance - S1
Fleet Maintenance - S2
Fleet Maintenance - S3
Fleet Maintenance - S4
Fleet Maintenance - S5
Fleet Maintenance - S6
Fleet Maintenance - S7
Fleet Maintenance - S8
Fleet Maintenance - S9
Fleet Maintenance - S10
Fleet Maintenance - S11
Fleet Maintenance - S12
Fleet Maintenance - S13
Fleet Maintenance - S14
Fleet Maintenance - S15
Fleet Maintenance - S16
Fleet Maintenance - S17
Fleet Maintenance - S18
Fleet Maintenance - S19
Fleet Maintenance - S20
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