Spicer Drive Axles Application Guidelines - Manual (Page 94)

AXAG-0200 June 2009 94
Glossary
Camber, Positive
- Top of the wheel tilts outward.
Cam Roll-over
- Jargon denoting that an S-cam has
traveled beyond its designed stopping position during
brake application. The wheel end must be removed to
repair cam roll-over. It is caused by a combination of
excessively worn lining and drum.
Cam Same/Opposite Drum Rotation
- As can be seen in
this force vector comparison, the direction of the
application force is different between cam same and cam
opposite. In the cam same, the cam rotation is in the same
direction as drum rotation. In the cam opposite, the
primary shoe roller is pushed out and up which tends to
allow the cam end of the shoe to be pushed against the
drum instead of the center of the shoe. This allows the
shoe to energize itself and increases torque output
(slightly) over a cam same brake. Also in some cases with
certain combinations of hardware and lining materials,
cam opposite brakes are noisy. Of course the question
comes to mind "why have a cam opposite brake if it is a
disadvantage"? The answer is that some suspension
systems do not have enough clearance to allow chamber
brackets to be mounted in the proper location to allow cam
same brakes.
Cam UH Length
- On DAP trailer axles, the length as
measured from under the brake cam head to the end of the
drum.
Cardan Universal Joint
- A non-constant universal joint
consisting of two yokes joined by a cross.
Carrier
- Portion of the axle assembly that contains the
drives gears and differential.
Caster
- Tilt of the kingpin centerline looking from the
side - offers directional stability and assists in returning
wheels to a straight ahead position through self centering
action.
Caster, Negative
- Kingpin centerline projected behind
the road contact point.
Caster, Positive
- Kingpin centerline projected ahead of
the road contact point.
Central Tire Inflation System
- See " CTIS ".
Channel, ABS
- The number of channels in an ABS
system refers to the number of valves its Electronic
Control Unit (ECU) is capable of independently
controlling.
1-Channel ABS
- A system design that uses two wheel
speed sensors and one control valve (2S/1M). This is the
most popular system for most trailers. It is called tandem
control.
2-Channel ABS
- A system design that uses two or four
wheel speed sensors and two control valves (2S/2M or 4S/
2M). The ABS monitors wheel speed and avoids wheel
lock-up on one axle while braking on low-friction surfaces
or in emergency situations by rapidly cycling the brakes
on the wheel ends of two axles. Commonly used on
trailers
4-Channel ABS
- A system design that uses four wheel
speed sensors and four ABS control valves (4S/4M) on a
two-axle truck or tractor . A 4-channel system can also be
used on a three-axle vehicle, controlling the left and right
side drive axle wheels in pairs. This popular system, which
offers an optimum blend of performance and economy, is
the most common system on trucks, tractors and buses.
6-Channel ABS
- A system design that features six wheel
speed sensors and six ABS control valves (6S/6M) to
individually monitor and control all six wheels of a three-
axle truck or tractor . This type of system provides the
highest available level of ABS control. Its commonly used
on vehicles with lift or tag axles.
Check Valve
- A one-way check valve is used, for
example, to prevent air from bleeding back out of a
reservoir. A two-way check valve activates selectively; for
instance, by drawing air for brake application from the
most-highly-pressurized reservoir (primary or secondary).
Clearance Sensing Brake Adjuster
- Senses force when
brake lining contacts the drum to adjust lining to drum
clearance.
Clevis Pin
- Pin connecting the arm of a slack adjuster to a
brake chamber push rod yoke.
CMVSS 121 (Canadian Motor Vehicle Safety Standard
121)
- Standard for air brake vehicles.
Combination
- Truck coupled to one or more trailers.
Combination Lining Block
- Two different lining
materials on the same brake shoe. The higher friction
material is on the cam end of the brake shoe with the lower
friction material on the anchor end.