Troubleshooting guide

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Super single tire — Specially designed tires used in lieu
of dual tires in certain vehicle vocations. Super singles can
reduce maintenance and/or save hundreds of pounds of tire
weight when compared to duals.
Supply air reservoir (tank) — The air reservoir immediately
downstream of the air compressor. Also known as the wet tank,
where water and oil are most likely to accumulate (assuming
the lack of a functional air dryer).
TCS — Traction Control Systems. Just as antilock helps
vehicle control and stability during braking, traction control
helps during vehicle acceleration at low speeds. With traction
control, a spinning wheel is instantly detected, and the system
intervenes to reduce wheel slip and improve driveability.
Thermal balance — This is achieved when all brakes on a
vehicle are operating at the same temperature. If the correct
thermal balance was achieved, both the tractor and trailer
brakes would see the same temperature throughout any
given braking cycle. On some vehicles, steer axle brake
temperatures should be somewhat below drive brakes to avoid
aggressiveness and pull. Note that for certain advanced ABS
interventions, braking is applied at individual wheel-ends and
so the thermal balance will be affected temporarily.
Timing balance — This is achieved when all brake chambers,
within an appropriate time from application, are receiving the
required air pressure. Due to the nature of long vehicle air
systems, air cannot be expected to arrive at all axles at exactly
the same time in a purely pneumatically-controlled braking
system.
TMC — The Technology & Maintenance Council; an
organization consisting of government agencies, independent
truckers, truck manufacturers, fl eet operators, component
manufacturers, media and academia. TMC's primary goal
is to communicate the latest and best vehicle maintenance
procedures to the end users. These developed maintenance
procedures are communicated to the trucking industry in the
form of Recommended Practices (RPs).
Tone Ring — A ring that is usually pressed into a wheel hub
that has a series of teeth (usually 100) and provides actuation
for the speed sensor. Note maximum run out is .008.
Torque balance — This is achieved when individual brakes
exert the degree of braking force required for each brake in the
system to do its fair share of the work.
Tractor protection — Upon accidental separation of trailer(s),
a tractor protection system prevents air loss from the power
unit, thereby protecting the tractor service brakes.
Tractor protection valve — Isolates tractor air system in the
event of a trailer breakaway, or dangerous decrease in the
tractor's reserve air, but is typically applied (via dash-mounted
control) before disconnecting a trailer.
Trailer control valve — This is a hand-operated valve,
located on (or adjacent to) the steering column, which permits
independent control of the trailer brakes. Also known as the
trolley valve or hand valve.
Trailer push — This is typically caused by the tractor braking
before the trailer and/or with greater torque. Even with ideal
brake balance, the trailer tends to push the tractor to some
extent, since the tractor brakes absorb part of the trailer's load.
TRDU — Trailer Remote Diagnostic Unit. A hand-held diagnostic
tool used on trailers.
Treadle valve — A foot-operated brake actuation valve.
Trolley valve — See Trailer control valve.
TRSP—Trailer Roll Stability Program.
Warning light/ABS — An indicator light on the truck or tractor
instrument panel that illuminates to indicate the status of
the ABS systems (truck, tractor, trailer). On trailer ABS, an
indicator light must also be located on the trailer body where
the driver or maintenance personnel can easily see it.
Wet tank (or supply air tank) — That reservoir nearest to the air
compressor where water and oil are most likely to accumulate
(assuming the lack of a functional air dryer).
Wide brake package — A brake combination with wider-than-
normal shoes and drums to increase the ability to absorb energy
thereby increasing the time between brake lining replacement.
Yaw Control — Helps stabilize rotational dynamics of the
vehicle.
Glossary, continued
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