CAD- Center Axle Disconnect. A device that disconnects one front axle shaft (usually the long one) from the differential via a splined, sliding collar. It's commonly actuated by engine vacuum, but can also be cable or hydraulically operated. The idea is to reduce the parasitic drag of the front axle, prevent the driveshaft from turning in 2-wheel drive and was conceived as an alternative to locking front hubs. This system only works with open diffs and it still allows the differential side and spider gears in the differential to rotate. If a limited slip or locker is installed, the left axle will then drive the ring and pinion and the driveshaft, usually causing a vibration at higher speeds.
CAD
Camber- The built in curve or arch in a leaf spring. Also a steering term indicating the inward or outward tilt of the tops of the front tires. Positive camber tilts them out (as viewed from the front) and negative camber tilts them in.
Camber Roll- The increase in camber that comes when the vehicle is steered hard to one side or another.
Cardan Joint- The original name for the common Spicer-style universal joint, named for the 16th century Italian mathematician, Jerome Cardan, who established their basic principle of operation.
Caster- The forward or backward tilt of the steering axis. Positive caster tilts the top pivot from the vertical towards the rear of the vehicle and negative is the opposite.
Center of Gravity- The point of a vehicle where it balances on all planes. On most rigs, that point is somewhat forward of center and one to two feet off the ground, when viewed from the side, and slightly off to one side when viewed from the top. A lower center of gravity makes for a vehicle that is resistant to rolling over.
Chunk- When a tire throws off small pieces of tread. Comes from heat and friction, but can occur when a tire is siped or when it's used in rocks.
Chunk
Compression- The amount of upward travel of a suspension above the static ride height.
Contact patch- The part of the tire that makes contact with the ground and provides traction. The patch varies according to the tire size and the tire pressure used.
Crossover SUV- Most commonly a car or minivan platform with, or adapted to, AWD.
Crossover Steering- The steering system in which the two steering knuckles at the wheel ends are tied together directly with one rod called the tie rod. A drag link comes down from the steering box and attaches to one knuckle or the other to supply the steering input.
Crossover Steering
Cross-Axled- When the front and rear axles are articulated opposite each other.
Crawl Ratio- Also known as final drive ratio. The maximum multiplied lowest gear ratio, to include first gear, transfer case low range and axle ratio. If there is another gearing device, that ratio is also added.
CV-Joint- Constant velocity joint. Several types exist, including the six ball Rzeppa (pronounced "Cheppa") joint, the similar Birfield type, the four-ball Bendix type and the Herrington type consisting of two Cardan or u-joints. The result of all of these is the smooth transmission of power with no vibration. They are used on driveshafts and steering axles.
CV Joint
Dead-Man- An anchor point to winch from. If can be just about any solid object capable of supporting the weight applied against it.
Death Wobble- An overly dramatic term describing a severe steering vibration.
Deep Gearing- See Low Gearing.
Deflection- Movement or compression of a spring. Also the amount the tire "gives" under load. Essentially, the difference between its free and unloaded radius and its fully loaded radius.
Departure angle- An imaginary line or angle at the rear of a vehicle between the contact point of the tires and the lowest part of the rear overhang. This angle dictates the height and steepness of the obstacle that the vehicle can descend, as well as the angle of the climb the vehicle can make without dragging tail.
Directional Stability- The ability (or lack thereof) of a tire (or vehicle) to maintain a straight line rather than following irregularities in the road.
Drag link- The steering rod that connects the steering box Pitman arm to the tie rod.
Droop- The amount of downward suspension travel below the normal ride height of the vehicle. A.k.a. jounce.
Drop Pitman Arm- A special type of Pitman arm that is lower than stock. This reduces drag link angularity and bump steer.
Duty Cycle- The period over which a device can be operated before damage or undesirable effects occur. A cycle of "on" time vs "off" time.
