Spicer Drive Axles Application Guidelines - Manual (Page 103)

AXAG-0200 June 2009 103
Glossary
Spline
- Series of parallel keys cut along the driveshaft that
mate with corresponding slots in hub or fitting. Also found
on brake camshaft interface to slack adjuster.
Split-coefficient Surface
- Also called split-
m
(split-
Mu), a road condition where one side of a lane has low
friction and the other has high friction (example, the left
side of the lane is ice covered, the right side is dry). A 2, 4
or 6-channel ABS system (antilock brake system) with
individual wheel control will provide optimum stability and
stopping-distance performance under these conditions.
Spring Brake
- Generally refers to a tandem-chamber
brake actuator that incorporates an air-applied service
brake chamber and an air-release/spring-applied parking or
emergency brake chamber. Spring brakes apply upon
sudden air loss (emergency mode) or activation of a dash-
mounted parking brake control. Spring brakes remain
applied until that chamber is recharged with air or the
spring is manually compressed or caged. The spring
portion is often referred to as the ‘piggyback’. Spring
brakes generally come in two types: double diaphragm or
piston.
Spring Mounting Centers
- See " SMC ".
Spring Pad
- Flat locator surface on the beam that is
drilled for the specific mounting pattern for the U-bolt
connection to the leaf spring.
Static Loaded Radius
- See " SLR ".
Steerable Drive Axles
- See " Driving Axles, Steerable ".
Steer Arm
- Rigid connection between the steering
mechanism and the steer knuckle.
Steer Arm Ball Stud
- Tapered round ball mounted in the
steer arm providing a means of articulation when the drag
link transmits steering motion from the steering gear, that is
mounted on the frame to the steer axle which is mounted as
part of the suspension.
Steer Arm Swing Radius
- Radius created when the steer
knuckle rotates from stop to stop - establishes clearance
window.
Steering Gear
- The mechanism that translates the steering
wheel rotation into movement at the steer knuckle through
the draglink.
Steering Knuckle
- The inner portion of the spindle that is
connected to and pivots on the kingpin allowing the wheels
to turn while under load.
Stopping Distance
- The distance traveled by a vehicle on
a road between the initial brake pedal movement and a full
stop.
Stopping Time
- The time elapsed between the initial
brake pedal movement and a full stop.
Stop Screw
- A combination screw and lock nut
arrangement that limits the angular travel of the steer
knuckle in a steer axle.
Straight Truck
- A non-articulated vehicle that carries
cargo in a body mounted to its chassis, rather than on a
trailer towed by the vehicle.
Stroke
- Refers to a total distance traveled by a brake
chamber push rod or slack adjuster arm during brake
application.
Stroke Sensing ABA
- Excessive stroke caused by lining
wear raises the actuator rod during brake apply. The spiral
serrated activator will jump over serrations on the spring-
loaded pawl if adjustment is required. Actual brake
adjustment is made on the return stroke.
Stud Mount Wheels
- Wheels that are designed to center
on the studs of a hub. These wheels have chamfers at the
bolt holes into which a ball seat or conical nut is installed to
center the wheel. The center bore of the wheel is only for
clearance of the axle end.
Super Single Tire
- Specially designed tire used in lieu of
dual tires in certain line haul rigs and local gasoline
tankers. Super singles can reduce maintenance and/or save
hundreds of pounds of tire weight when compared to duals.
Also known as “Wide Base Tire”.
Supply Air Tank
- The air reservoir immediately
downstream of the air compressor. See " Wet Tank ".
Suspension
- Attaching parts including springs for
securing axle or axles to chassis frame.
Suspension Mounting Centers
- See " SMC ".
Swept Area
- The total surface area of the drum or rotor of
a brake that comes in contact with the friction material
during one revolution of the wheel. In general, the more
swept area a brake has, the cooler it will operate.
Tag Axle
- A non-driven (dead) axle installed behind the
drive axle(s) to increase the permissible gross weight, and
consequently the payload. Also termed "trailing axle."
Tandem Drive Axle
- Two-axle drive combination or dual
drive axles.
Taper
- Cone shaped object or form.
DISASSEMBLY OF A SPRING BRAKE IS
DANGEROUS. ONLY TRAINED MECHANICS
SHOULD ATTEMPT THE PROCEDURE.