"Super-Speak" Suspension Terms & Definitions

Lift Kit

A suspension lift or lift kit is a modification, often done by Jeep, truck, SUV and off-road enthusiasts to raise the ride height of their vehicle. Lift kits help accommodate larger tire and wheel combos and improve off-road performance. Each manufactured vehicle usually requires a specific lift kit, and the types of kits vary based on the type of drivetrain that the vehicle has. Kits can be as simple as replacement leaf springs, coil spring/strut spacers, and extended shocks; to replacement control arms, drop down brackets, lift spindles and other related components. Suspension lifts could also impact other factors, such as drive shaft length, steering geometry and brake lines.

Leveling Kit

Leveling Kits are the perfect solution for anyone wanting an economical and easy way to eliminate the factory nose-down rake on virtually all late-model trucks and SUVs. Leveling kits are also the ticket for people wanting to make room for little larger tire and wheel package. Leveling kits work with factory suspension components to achieve modest ride height gains without a lot of hassle. These systems are simple and effective, with installation times normally around only two hours. The leveling kits provide 1-1/2" to 3" of lift height depending on the application via components that are precision-engineered and easy to install.

Long Arm Suspension

On a 4-link or radius arm suspension, when the factory links or arms are replaced with longer units, this is termed a long arm suspension conversion. Longer arms result in less geometry change, as the suspension travels, which improves drivability, plus they allow more bind-free suspension travel.

Military Wrap

Featured in some leaf spring designs, the second leaf plate wraps around the spring eye (called the main leaf) to form a double-wrap. This design element transmits less stress to the main leaf during extreme articulation. It also lessens the odds of spring separation in case of main leaf failure and provides greater strength, support, and durability as a whole.

OEM

Acronym for Original Equipment Manufacturer. For example Ford, GM, Chrysler, etc.

Pitman Arm

A pitman arm connects the steering box to the truck’s steering linkage. This steering component splines onto the steering sector output shaft. The opposite end connects to a drag link or centerlink, depending on steering system type. With a "dropped" pitman arm, the drag link attachment point is moved down to corrects steering geometry by reducing the drag-link angle in relation to the tie rods on lifted 4x4s

Pre-set Coil Springs

Pre-setting involves fully compressing the coil spring (so that the coil wraps are actually touching each other) in the manufacturing process. This reduces the amount of coil sag and extends coil service life.

Progressive Rate Coils

Most coil springs have rates that are constant; if it takes 400 pounds to compress the spring the first one inch, another 400 pounds will compress it the second inch, and so on. With a progressive rate coil, spring rate for the initial couple inches of compression is less than the spring rate for the remainder of compression. This improves your "Sunday drive" ride quality, yet rate can still accommodate more aggressive driving. On progressive rate springs, the first few coil wraps are more closely spaced than the remaining coils or the entire spring is slightly conical (cone-like) in shape.

Radius Arm

The radius arms (one per side) run basically parallel to the frame rails. They locate the front axle housing and prevent fore and aft axle movement. Common vehicles factory equipped with radius arms are 1966-79 Fords with coil spring / solid axle suspension, 1980-96 Fords with coil spring TTB, and 2005 and newer Super Duty. Caster angle must be addressed when lifting vehicles with radius arms.

Roll and Yaw

The problem exists on lifted vehicles that have incorrect track bar length and/or severe track bar angle. When lifted past a certain point, the track bar should be lengthened or binding occurs as the suspension travels. If unaddressed, the frame and axle housing will continuously "tug" against each other. This is most noticeable when the vehicle is being driven in a straight line, going through highway dips at speed. The sensation compares to the side-to-side oscillations of a boat. A certain amount of "steering wheel kick" normally accompanies roll and yaw.

Solid Axle

A one-piece axle housing design that has rigid axle tubes all the way out to the knuckles. Examples of vehicles with solid front axles are 1966-79 Fords and 1969-87 GM trucks.

Spring Rate

A measurement of force (in pounds) required to compress a spring a given distance (in inches). Be careful when comparing rates since all manufacturers do not use the same measuring procedures.

Steering Arm

This forged steel component bolts to the front axle knuckle. Its opposite end attaches to the drag link. A raised steering arm is taller to reduce drag link angle. Steering blocks can also be used to alleviate drag link angle.

Steering Block

A steering block relieves drag link angle by positioning between the factory steering arm and steering knuckle.

Steering Wheel Kick

This malady is most noticeable when you are driving in a straight line and the suspension compresses, like when going through a highway dip at speed. The steering wheel will move slightly, but the vehicle continues to track straight ahead. If the vehicle has a track bar, the problem is related to incorrect track bar length (too short) and/or incorrect phasing. Incorrect phasing exists when the track bar arc-of-movement is not in phase with the drag link arc-of-movement. Incorrect phasing can result when a dropped pitman arm is used, but the track bar is not properly relocated. A certain amount of phasing miss-match is acceptable, but at some point "kick" will occur.

Strut Assembly

Found on many late-model IFS vehicles, a strut assembly consists of a coil spring that attaches to a strut body (shock absorber). Coilover shocks are used to replace struts when more coil rate and height adjustability is desired.

Stud Bind

Occurs when a tapered stud, normally a tie rod or track bar end, over-extends its pivot capability. This is a byproduct of excessive operating angles.

Suspension Travel

The amount of available wheel travel from full compression to full extension.

Sway Bar, Sway Bar Links

Also referred to as a stabilizer bar or an anti-sway bar. The sway bar assembly consists of a U-shaped tubular body that spans the width of the vehicle frame, and two links (one per side) that connect the body to an anchor point on the axle or control arm. Generally, at a certain lift height, either the bar body is relocated, or longer links are used, to prevent sway bar preload.

Sway Bar Pre-Load

As lift height increases the sway bar body pivots and begins to pre-load. This pre-load puts extra stress on the links, which limits additional suspension travel and flexibility. Proper bar geometry is restored by relocating the body or by using longer links.

T-Case

Short for a transfer case. A device usually attached directly to the transmission. The transfer case is a gearbox that splits engine power to the front and rear axles. You can select two-wheel-drive or four-wheel-drive high or low range with most transfer cases.

Tie Rod

A section of steering linkage. All outer tie rod ends attach directly to the knuckle.

Toe Angle

A steering geometry term, this refers to the difference in track width measurements taken at the front side and rear side of the front tires. If the measurement is less at the front, it is termed Toe-In. If the measurement is less at the rear, it is termed Toe-Out.

Track Width

The distance between two wheels that are on the same axle, as measured from the center-points of left- and right-side wheels.

Track Bar

Found on basically all coil spring equipped vehicles that have solid axles, and most later-model leaf spring equipped vehicles. The bar helps locate and stabilize the body/frame, in relation to the axle housing. Generally, when lift exceeds 2", the bar must be relocated and/or replaced with a longer, adjustable unit.

Traction Control

Most modern 4x4 vehicles will have some level of traction control. It could have a simple on/off setting, or a complex system with multiple settings programmed for different traction situations. No matter the system, traction control uses either the brakes and/or the 4x4 mechanicals to limit wheel slip and ensuring torque is being transferred from the tire to the trail... Since there are so many kinds of traction control systems, we encourage you to read up on yours and its many settings in your owner's manual.

TTB

Acronym for Twin Traction Beam, Ford's Independent Front Suspension system found on most 1980 to 1996 models.

Turning Radius

A measurement of the distance required to turn a vehicle in a full circle.

Wheel Base

Distance from the center of a vehicle's front wheel to the center of its rear wheel on the same side of the vehicle. Vehicles with longer wheelbases offer a smoother ride, but shorter wheelbases prove advantageous on uneven trails because the center of the vehicle is less likely to become stuck in a high-centered position.

Wrap-Up

Referred to as both rear spring and rear axle wrap-up. As power is applied, torque load causes the rear pinion to pivot upward. Once this load reaches a certain point the leaf springs begin to deform, and wheel-hop is induced. The "fix" is to increase spring strength or to reduce leverage by decreasing lift block height.

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