Spicer Drive Axles Application Guidelines - Manual (Page 104)

AXAG-0200 June 2009 104
Glossary
Thermal Balance
- Is achieved when all brakes are
operating at the same temperature. If the proper thermal
balance is achieved both the tractor and trailer brakes 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.
Threaded Drum
- Brake drum improperly resurfaced on a
lathe, resulting in a friction surface akin to that of a scored
drum.
Thrust Bearing
- These bearings are designed to carry
only thrust loads.
Tie Rod Arm
- The arm that is rigidly connected to the
steer knuckle that ties the LH knuckle to the RH knuckle
and also sets up the steering / Ackermann geometry.
Tie Rod Arm Angle
- The angle formed in the horizontal
plane between the vertical plane formed by the kingpin
intersection / pivot point and the tie rod arm mounting hole
where the tie rod end attaches.
Tie Rod End
- Threaded part with a ball socked for
articulation which attaches in the cross tube for adjustment.
Each end is threaded the opposite of the other.
Tie Rod Offset
- The distance from the kingpin
intersection / pivot point to the tie rod arm mounting hole
where the tie rid end attaches in the lateral direction.
Timing Balance
- Is achieved when all brake chambers are
receiving the required air pressure within an appropriate
time from application. Due to the nature of long vehicle air
systems, air cannot be expected to arrive at all axles at the
exact same time.
Tire Pressure Controls
- See " CTIS ".
Tire Rolling Radius
- See " SLR ".
TMC (The Maintenance Council)
- An organization
consisting of fleet operators, independent truckers, truck
manufacturers, component manufacturers, government
agencies, media and academia whose primary goal is to
communicate the latest and best vehicle maintenance
procedures to the end users. These maintenance procedures
are communicated to the trucking industry in the form of
Recommended Practices (RP).
TMS (Tire Maintenance System)
- Keeps tires properly
inflated.
Toe
- The difference between the tire centerline-to-
centerline distances in the front versus the rear of steer axle
tires.
Toe-in (Positive toe)
- Tires are pointing in as seen from
the front - provides straight-line directional stability.
Toe-out (Negative Toe)
- Tires are pointing out as seen
from the front - will result in "road wander".
Top Mount Suspension
- A trailing arm suspension in
which the trailing arm is mounted to the top of the axle.
Torque Balance
- 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.
Torque Converter
- A hydraulic drive that transmits
power with ability to change torque.
Torque Plate
- A plate used to mount the disc brake caliper
to the axle brake flange or steer knuckle.
Torsional Driveline Acceleration
- Each universal joint in
a driveshaft rotates non-uniformly. This non-uniformity is
minimized or eliminated by the proper relative positioning
(phasing) of the universal joint yokes at either end of the
driveshaft.
Torsional Excitation
- Excitation produced by the non-
uniform velocity obtained when a Cardan joint operates at
an angle.
TPCS
- Tire Pressure Control System - a means of easily
adjusting the vehicle tire pressure, both inflate and deflate,
for the conditions encountered whereby improving vehicle
mobility performance. TPCS is used primarily in the
commercial vocation market, on/off highway.
Track
- The distance between the dual tire centerlines on a
dual tire arrangement or the distance between the tire
centerlines on a single tire arrangement.
Tractor
- Truck portion of combination or train.
Tractor Protection Valve
- Isolates tractor air system in
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
- 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
- Caused by the tractor braking prior to the
trailer and/or with greater torque. Even with "perfect"
brake balance, the trailer pushes the tractor to some extent
since the tractor brakes absorb part of the trailer's load.
Trailer Swing
- Articulation of the trailer caused by
locking the trailer brakes.