Finesse 1 -2 -3: Four Wheeling Encyclopedia: A thru D

Story & Photos by Jim Allen
This long-running "Four Wheel Finesse" column is all about fundamentals in four wheeling. Like Bricklaying...when you understand how that first row is laid, the rest of the job is just an extension of that basic concept.
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This long-running Four Wheel Finesse column is all about fundamentals in four wheeling. Like bricklaying... when you understand how that first row is laid, the rest of the job is just an extension of that basic concept.

A-Arm- A triangular suspension component used on independent suspensions. Also could be called a control arm, upper or lower. It pivots on the chassis at two points, the wide end of the "A," and the pointy end attaches to the spindle.

ABS- Anti-Lock Braking System. An electronically controlled system that prevents skidding under hard braking by controlling and equalizing wheel speed. A two-channel system controls only two wheels, the rear, while a four-channel system controls all four wheels.

 
Ackerman Angle- A.k.a. toe-out on turns. An engineered value that allows the inner wheel to steer a great amount than the outer because the inner wheel covers a shorter path.

Add-a-Leaf- An inexpensive method of lift where an additional leaf is added to the leaf spring pack to provide a small amount of lift at the cost of ride quality.

Aftermarket- Vehicle parts or equipment not manufactured by the OE manufacturer.

Amp Draw- The number of ampere-hours (amp hours) needed to run an electrical device.

Approach Angle
Approach Angle- The maximum angle of climb that a vehicle can surmount without hitting some part of the body, chassis or mechanicals in the front.

Arch- See camber.
 
Articulated- When one tire is at its upper travel and the other at its lowest travel and the axle is at a severe angle in relation to the body. See also Cross-Axled and Articulation.

Articulation
Articulation- The ability of a suspension to combine compression and droop on one axle. If a suspension articulates well, the body will stay relatively level but the axles will operate at severe angles.

Aspect Ratio- The ratio between the tire's width and height. Expressed as a percentage, it represents the tire's profile or the distance between the tread and the rim versus its section width.

Axle Wrap- Torque and traction combine to twist the axle (pushing the nose of the differential up going forward and down going backward) by twisting the axle into an "S" shape. The energy is stored in the spring until the tire slips, and at that point the spring snaps back violently. Sometimes this results in a hopping sensation, hence the other common term, "axle hop." It can be very hard on driveshafts and u-joints.

Backspacing
Backspacing- Another term for wheel offset. It's the distance from the inside edge of the wheel to the mounting flange.

Bead- The area that mates the tire to the wheel. This area is a critical part of the tire's construction and consists of a hoop of high tensile steel wires to which the belts are attached. This anchors the belts as well as providing a firm grip on the rim.

Bead Seat- This is the smooth face on the bead area of the tire that seals against the rim to hold air.

Bead Filler- A solid rubber wedge built into the lower sidewall designed to stiffen the area near the bead

Beadlock- A type of wheel rim that prevents the tire from sudden deflation when used at low pressure.

Beater- A 4x4 in rough condition. Usually one that looks bad but runs good.

Beef- Strength. Also adding strength to a part: upgrading.

Binder- Short for "Cornbinder." Slang for vehicles built by the International Harvester Company.

Birfield- Another name for a six-ball constant velocity joint, usually used by Toyota or other Japanese 4x4 enthusiasts. The original design came from Hans Rzeppa in the 1920s but one of the later manufacturers was Birfield Ltd. in England. The Birfield joint was introduced in the Toyota Land Cruiser in the 1960s. It isn't clear whether they were produced in Britain or under license in Japan but the tooling to make these CV joints was elaborate and expensive. Many of these CV joints were stamped "Birfield."

Blip- A quick, "on/off" stab of the throttle.

Bogger- A vehicle built for running mud. Also another term for an aggressive mud tire.

Bolt Clips- A device uses to keep the spring leaves lined up atop
each other. This is the preferred method of doing this because it does not restrict the movement as the "cinch" type clamps may do.

Bottom- Compressing the suspension to the point where it reaches the bump stops.

Boxing- Usually refers to chassis modifications, where it is reinforced by closing the open part of a "C" or "U" section with additional material. It adds considerably to the strength.

Built- Short for built-up, or heavily modified.

Bump Steer- Where a bump or movement of the suspension forces the steering system to steer to one side or the other. Accompanied by movement of the steering wheel. Can occur at low speeds as the suspension moves up or down, or can occur at speed when bumps are encountered. It occurs to most 4x4s to a certain degree at low speeds, but at speed, it can be dangerous.

Bump Stop- A rubber or polyurethane bumper that limits the compress point or upward travel of the wheel.

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