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Ride Control Defined

According to Newton's First Law, a moving body will continue moving in a straight line until it is acted upon by another force. Newton's Second Law states that for each action there is an equal and opposite reaction. In the case of the automobile, whether the disturbing force is in the form of a wind-gust, an incline in the roadway, or the cornering forces produced by tires, the force causing the action and the force resisting the action will always be in balance.

Many things affect vehicles in motion. Weight distribution, speed, road conditions and wind are some factors that affect how vehicles travel down the highway. Under all these variables however, the vehicle suspension system including the shocks, struts and springs must be in good condition. Worn suspension components may reduce the stability of the vehicle and reduce driver control. They may also accelerate wear on other suspension components.

Replacing worn or inadequate shocks and struts will help maintain good ride control as they:

  • Control spring and suspension movement
  • Provide consistent handling and braking
  • Prevent premature tire wear
  • Help keep the tires in contact with the road
  • Maintain dynamic wheel alignment
  • Control vehicle bounce, roll, sway, dive and acceleration squat
  • Reduce wear on other vehicle systems
  • Promote even and balanced tire and brake wear
  • Reduce driver fatigue

Suspension concepts and components have changed and will continue to change dramatically, but the basic objective remains the same:

  1. Provide steering stability with good handling characteristics
  2. Maximize passenger comfort

Achieving these objectives under all variables of a vehicle in motion is called ride control

Back to TopBasic Terminology

To begin this training program, you need to possess some very basic information. The chassis is what connects the tires and wheels to the vehicle's body. The chassis consists of the frame, suspension system, steering system, tires and wheels.

  • The frame is the structural load-carrying member that supports a car’s engine and body, which are in turn supported by the suspension and wheels.
  • The suspension system is an assembly used to support weight, absorb and dampen road shock, and help maintain tire contact as well as proper wheel to chassis relationship.
  • The steering system is the entire mechanism that allows the driver to guide and direct a vehicle.

The side to side distance between the centerline of the tires on an axle is called track. The distance between the centerline of the front and rear tires is called wheelbase. If the vehicle is in proper alignment, the wheels will roll in a line that is parallel with the vehicle’s geometric centerline.

You should also understand that tires and wheels make vehicle motion possible. The amount of grip or friction between the road and the tires is the major factor that limits how the vehicle accelerates, maneuvers through corners, and stops. The greater the friction, the faster the car can accelerate, corner and stop.

The tire to road contact of a vehicle is affected by several forces. Vehicle dynamics is the study of these forces and their effects on a vehicle in motion. Our discussion will concentrate on how these forces affect handling with some consideration given to how they affect acceleration and deceleration.

Fundamentals Of Handling

Vehicle geometry, suspension, and steering design all affect the handling of a vehicle. To better understand the term “handling,” we can address the following fundamentals that contribute to good handling:

Road Isolation

Road isolation is the vehicle’s ability to absorb or isolate road shock from the passenger compartment. The degree to which this is accomplished is controlled by the condition of the suspension system and its components. A properly functioning suspension system allows the vehicle body to ride relatively undisturbed while traveling over rough roads. This is accomplished through the combined use of bushings, springs, and hydraulic dampers.

The springs support weight as the vehicle travels down the road. When a vehicle encounters a bump in the road, the bushings receive and absorb the inputs from the road, while the springs compress and store kinetic energy. This energy is then released, causing a rebound in the vehicle’s weight. The rate at which the springs compress and rebound is controlled using a hydraulic damper, such as a shock absorber or strut. The result of this action is to limit the amount of road input felt in the passenger compartment.

Road Holding

Road holding is the degree to which a car maintains contact with the road surface in various types of directional changes and in a straight line. Remember that the vehicle’s ability to steer, brake, and accelerate depends first and foremost on the adhesion or friction between the tires and the road.Tire force variation is a measure of the road holding capability of the vehicle and is directly influenced by shock absorber or strut performance. Shock absorbers and struts help maintain vertical loads placed on the tires by providing resistance to vehicle bounce, roll and sway during weight transfer. They also help reduce brake dive along with acceleration squat to achieve a balanced ride.

Worn shocks and struts can allow excessive vehicle weight transfer from side to side and front to back, which reduces the tire's ability to grip the road. Because of this variation in tire to road contact, the vehicle’s handling and braking performance can be reduced. This may affect the safe operation of the vehicle and the safety of those riding inside. Therefore, shocks and struts are safety components.

Tire loading changes as a vehicle's center of gravity shifts during acceleration, deceleration, and turning corners. The center of gravity is a point near the center of the car; it is the balance point of the car.

The size of the four contact patches of traction at the tires also varies with the changes in tire load. As the vehicle brakes, inertia will cause a shift in the vehicle’s center of gravity and weight will transfer from the rear tires to the front tires. This is known as dive. Similarly, weight will transfer from the front to the back during acceleration. This is known as squat.

Consistently controlling vehicle weight transfer and suspension movement enhances the road holding capability of the vehicle and ultimately its safe operation.

Cornering Cornering is defined as the ability of the vehicle to travel a curved path. It is also referred to as cornering power or lateral acceleration. Many things can affect the cornering ability of a vehicle, such as:

  • Tire construction
  • Tire tread
  • Road surface
  • Alignment
  • Tire loading

As a vehicle turns a corner, centrifugal force pushes outward on the car’s center of gravity. Centrifugal force is resisted by the traction of the tires. The interaction of these two forces moves weight from the side of the vehicle on the inside of the turn to the outside of the car, and the car leans. As this occurs, weight leaves the springs on the inside and that side of the vehicle raises. This weight goes to the springs on the outside, and that side of the vehicle lowers. This is what is known as body roll

When the cornering requirement of a particular maneuver is less than the traction that can be provided by the tires, the car will go where it is pointed and steered. However, if the cornering force exceeds the available traction from the tires, the tires will slip across the road surface and they will skid.

Purpose Of The Suspension System

As we review suspension system components and how they work together, remember that a vehicle in motion is more than wheels turning. As the tire revolves, the suspension system is in a dynamic state of balance, continuously compensating and adjusting for changing driving conditions. Today's suspension system is automotive engineering at its best.

The components of the suspension system perform six basic functions:

  1. Maintain correct vehicle ride height
  2. Reduce the effect of shock forces
  3. Maintain correct wheel alignment
  4. Support vehicle weight
  5. Keep the tires in contact with the road
  6. Control the vehicle’s direction of travel

However, in order for this to happen, all the suspension components, both front and rear, must be in good working condition.

Back to TopMain Components Of A Modern Suspension System

At this point, it's important to understand that the main components of a moving vehicle suspension system are the Struts, Shock Absorbers, Springs and Tires. We will first turn our attention to the design and function of springs. In the following section we will thoroughly examine the function and design of shock absorbers and strut assemblies.

The springs support the weight of the vehicle, maintain ride height, and absorb road shock. Springs are the flexible links that allow the frame and the body to ride relatively undisturbed while the tires and suspension follow the bumps in the road.

Springs are the compressible link between the frame and the body. When an additional load is placed on the springs or the vehicle meets a bump in the road, the springs will absorb the load by compressing. The springs are a very important component of the suspension system that provides ride comfort. Shocks and struts help control how fast the springs and suspension are allowed to move, which is important in keeping tires in firm contact with the road.

During the study of springs, the term bounce refers to the vertical (up and down) movement of the suspension system. The upward suspension travel that compresses the spring and shock absorber is called the jounce, or compression. The downward travel of the tire and wheel that extends the spring and shock absorber is called rebound, or extension.

When the spring is deflected, it stores energy. Without shocks and struts the spring will extend and release this energy at an uncontrolled rate. The spring's inertia causes it to bounce and overextend itself. Then it re-compresses, but will again travel too far. The spring continues to bounce at its natural frequency until all of the energy originally put into the spring is used.

If the struts or shock absorbers are worn and the vehicle meets a bump in the road, the vehicle will bounce at the frequency of the suspension until the energy of the bump is used up. This may allow the tires to lose contact with the road.

Struts and shock absorbers that are in good condition will allow the suspension to oscillate through one or two diminishing cycles, limiting or damping excessive movement, and maintaining vertical loads placed upon the tires. This helps keep the tires in contact with the road.

By controlling spring and suspension movement, components such as tie rods will operate within their design range and, while the vehicle is in motion, dynamic wheel alignment will be maintained.

Spring Designs

Before discussing spring design, it is important to understand sprung and unsprung weight. Sprung weight is the weight supported by the springs. For example, the vehicle's body, transmission, frame, and motor would be sprung weight. Unsprung weight is the weight that is not carried by springs, such as the tires, wheels, and brake assemblies.

The springs allow the frame and vehicle to ride undisturbed while the suspension and tires follow the road surface. Reducing unsprung weight will provide less road shock. A high sprung weight along with a low unsprung weight provides improved ride and also improved tire traction.

There are four major spring designs in use today: coil, leaf, torsion bar, and air.

Coil Springs The most commonly used spring is the coil spring. The coil spring is a length of round spring steel rod that is wound into a coil. Unlike leaf springs, conventional coil springs do not develop inter-leaf friction. Therefore, they provide a smoother ride.

The diameter and length of the wire determine the strength of a spring. Increasing the wire diameter will produce a stronger spring, while increasing its length will make it more flexible.

Spring rate, sometimes referred to as deflection rate, is used to measure spring strength. It is the amount of weight that is required to compress the spring 1 inch. For example: If it takes 100 lbs. to compress a spring 1inch, it would take to 200 lbs. to compress the spring 2 inches.

Some coil springs are made with a variable rate. This variable rate is accomplished by either constructing this spring from materials having different thickness or by winding the spring so the coil will progressively compress at a higher rate. Variable rate springs provide a lower spring rate under unloaded conditions offering a smoother ride, and a higher spring rate under loaded conditions, resulting in more support and control.

Coil springs require no adjustment and for the most part are trouble-free. The most common failure is spring sag. Springs that have sagged below vehicle design height will change the alignment geometry. This can create tire wear, handling problems, and wear other suspension components. During suspension service it is very important that vehicle ride height be measured. Ride height measurements not within manufacturer’s specifications require replacement of springs.

Leaf Springs Leaf springs are designed two ways: multi-leaf and mono-leaf. The multi-leaf spring is made of several steel plates of different lengths stacked together. During normal operation, the spring compresses to absorb road shock. The leaf springs bend and slide on each other allowing suspension movement.

An example of a mono-leaf spring is the tapered leaf spring. The leaf is thick in the middle and tapers toward the two ends. Many of these leaf springs are made of a composite material, while others are made of steel.

In most cases leaf springs are used in pairs mounted longitudinally (front to back). However, there are an increasing number of vehicle manufacturers using a single transverse (side to side) mounted leaf spring.

Torsion Bar Another type of spring is the torsion bar. The torsion bar is a straight or L shaped bar of spring steel. Most torsion bars are longitudinal, mounted solidly to the frame at one end and connected to a moving part of the suspension at the other. Torsion bars may also be transverse mounted. During suspension movement, the torsion bar will twist, providing spring action.

Air Springs

The air spring is another type of spring that is becoming more popular on passenger cars, light trucks, and heavy trucks. The air spring is a rubber cylinder filled with compressed air. A piston attached to the lower control arm moves up and down with the lower control arm. This causes the compressed air to provide spring action. If the vehicle load changes, a valve at the top of the airbag opens to add or release air from the air spring. An onboard compressor supplies air.

Tires as Springs

An often-overlooked spring is the tire. Tires are air springs that support the total weight of the vehicle. The air spring action of the tire is very important to the ride quality and safe handling of the vehicle. As a matter of fact, tires may be viewed as the number-one ride control component. Tire size, construction, compound and inflation are very important to the ride quality of the vehicle.

There are three basic types of tires: radial ply, bias ply, and bias belted.

Radial ply tires have ply cords, which run across the centerline of the tread and around the tire. The two sets of belts are at right angles. Some belts are made of steel wire; others are made of polyester or other substances. Today, radial tires come as original equipment on most passenger cars and light trucks.

Bias ply tires use cords that run at an angle across the centerline of the tire tread. The alternate ply cords cross at opposite angles. Bias belted tires are the same as bias ply, with the addition of layers of cords - or belts - circling the tire beneath the tread. Both of these types of tires will most likely be found on older model vehicles.

The air pressure determines the spring rate of the tire. An over inflated tire will have a higher spring rate and will produce excessive road shock. Over inflated tires will transmit road shock rather than reduce it. Over or under inflation also affects handling and tire wear.

When adjusting tire pressure, always refer to the vehicle manufacturer’s specifications, not the specification on the side of the tire. The air pressure specified by the vehicle manufacturer will provide safe operation and best overall ride quality of the vehicle. The tire pressure stamped on the side is the maximum pressure a tire is designed to hold at a specific load.

Strut Mount Design

Strut mounts are vehicle specific, and there are numerous designs in use today on both front and rear suspension systems. The three most common designs are inner plate, center sleeve, and spacer bushing.

The Inner Plate Design used by General Motors and some Ford applications feature an inner plate encased in molded rubber surrounded by upper and lower surface plates. The inner plate is designed so the strut piston rod cannot push through the upper or lower surface plate if the rubber core fails. This design generally does not require washers. Due to the fact that the upper and lower service plates mostly cover the rubber portion of the mount, it is difficult to see if the inner rubber bushing has failed. However, these components wear over time and with a thorough inspection a proper recommendation can be made. The bearing is located on the bottom of the strut mount and is not serviceable. Defective bearing will require replacement of the entire strut mount.

The Center Sleeve Design used by Chrysler features a center sleeve that is molded to the rubber bushing. This design provides increased side to side stability. The strut stem extends through the center sleeve. Upper and lower retainer washers prevent the strut rod from pushing through the strut mount. The bearing is a separate component from the strut mount. If inspection reveals cracks or tears in the rubber bushing, replacement is required. If the bearing is found to be defective it can be replaced separately.

The Spacer Bushing Design used by Volkswagen, Toyota, Mazda, Mitsubishi, and early Chrysler vehicles feature center positioning of the bearing and a separate inner bushing instead of a molded inner sleeve. The operation is similar to the style we just discussed except the bearing is pressed in the strut mount. The bearings, washer, and the upper plate retain the strut rod. If the rubber bushing is cracked, torn, or the bearing is binding or seized, the strut mount requires replacement.

Anti-Sway Bars

Another important component of a suspension system is the anti-sway bar. This device is used along with shock absorbers to provide additional stability. The anti-sway bar is simply a metal rod connected to both of the lower control arms. When the suspension at one wheel moves up and down the anti-sway bar transfers the movement to the other wheel. In this way the sway bar creates a more level ride and reduces vehicle sway or lean during cornering.Depending of the anti-sway bar thickness and design, it can provide as much as 15% reduction in the amount of vehicle roll or sway during cornering.


Bushings are used in many locations on the vehicle suspension system. Most bushings are made with natural rubber. However, in some cases, urethane compounds may be used. Bushings made of natural rubber offer high tensile (tear) strength and excellent stability at low temperatures. Natural rubber is an elastomeric material. Elastomeric refers to the natural elastic nature of rubber to allow movement of the bushing in a twisting plane. Movement is controlled by the design of the rubber element. Natural rubber requires no lubrication, isolates minor vibration, reduces transmitted road shock, operates noise free, and offers a large degree of bushing compliance. Bushing compliance permits movement without binding. Natural rubber resists permanent deflections, is water resistant and very durable. In addition, natural rubber offers high load carrying capabilities.

As with all suspension system components, control arm bushings are dynamic components, meaning that they operate while the vehicle is in motion. Control arms act as locators because they hold the position of the suspension in relation to the chassis. They are attached to the vehicle frame with rubber elastomeric bushings. During suspension travel, the control arm bushings provide a pivot point for the control arm. They also maintain the lateral and vertical location of the control arm pivot points, maintain dynamic wheel alignment, reduce transmitted noise, road shock, and vibration, while providing resistance to suspension movement.

During suspension travel the rubber portion of the bushing must twist to allow control arm movement. Control arm bushings that are in good condition act as a spring; that is, the rubber will spring back to the position from which it started. This twisting action of the rubber will provide resistance to suspension movement.

As previously stated, control arm bushings are dynamic suspension components. As the control arm travels through jounce and rebound, the rubber portion of the bushing will twist and stretch. This action transfers energy into the bushing and generates heat.

Excessive heat tends to harden the rubber. As the rubber bushing hardens, it tends to crack, break, and then disintegrate. Its temperature determines the life of a rubber bushing. Rough road conditions and/or defective shock absorbers or struts will allow excessive suspension movement creating more heat, which shortens the life of the bushings.

Rubber bushings must not be lubricated with petroleum-based oil. A petroleum-based product will destroy the bushings. Instead, use a special tire rubber lubricant or a silicone based lubricant.

Worn suspension bushings allow the control arm to change positions. This results in driveline vibration (primarily rear wheel drive rear control arm bushings), dynamic alignment angle changes, tire wear, and handling problems. Control arm bushing wear (looseness) will create a clunking sound while driving over rough roads.

Back to TopShock Absorbers

In the early 1900's, cars still rode on carriage springs. After all, early drivers had bigger things to worry about than the quality of their ride - like keeping their cars rolling over the rocks and ruts that often passed for roads.

Pioneering vehicle manufacturers were faced early on with the challenges of enhancing driver control and passenger comfort. These early suspension designs found the front wheels attached to the axle using steering spindles and kingpins. This allowed the wheels to pivot while the axle remained stationary. Additionally, the up and down oscillation of the leaf spring was damped by device called a shock absorber.

These first shock absorbers were simply two arms connected by a bolt with a friction disk between them. Resistance was adjusted by tightening or loosening the bolt.

As might be expected, the shocks were not very durable, and the performance left much to be desired. Over the years, shock absorbers have evolved into more sophisticated designs.

What Shocks Do

Let's start our discussion of shock absorbers with one of very important point: despite what many people think, conventional shock absorbers do not support vehicle weight. Instead, the primary purpose of the shock absorber is to control spring and suspension movement. This is accomplished by turning the kinetic energy of suspension movement into thermal energy, or heat energy, to be dissipated through the hydraulic fluid.

Shock absorbers are basically oil pumps. A piston is attached to the end of the piston rod and works against hydraulic fluid in the pressure tube. As the suspension travels up and down, the hydraulic fluid is forced through tiny holes, called orifices, inside the piston. However, these orifices let only a small amount of fluid through the piston. This slows down the piston, which in turn slows down spring and suspension movement.

The amount of resistance a shock absorber develops depends on the speed of the suspension and the number and size of the orifices in the piston. All modern shock absorbers are velocity sensitive hydraulic damping devices - meaning the faster the suspension moves, the more resistance the shock absorber provides. Because of this feature, shock absorbers adjust to road conditions. As a result, shock absorbers reduce the rate of:

  • Bounce
  • Roll or sway
  • Brake dive and Acceleration squat

Shock absorbers work on the principle of fluid displacement on both the compression and extension cycle. A typical car or light truck will have more resistance during its extension cycle then its compression cycle. The compression cycle controls the motion of a vehicle's unsprung weight, while extension controls the heavier sprung weight.

Compression cycle During the compression stroke or downward movement, some fluid flows through the piston from chamber B to chamber A and some through the compression valve into the reserve tube. To control the flow, there are three valving stages each in the piston and in the compression valve.

At the piston, oil flows through the oil ports, and at slow piston speeds, the first stage bleeds come into play and restrict the amount of oil flow. This allows a controlled flow of fluid from chamber B to chamber A.

At faster piston speeds, the increase in fluid pressure below the piston in chamber B causes the discs to open up away from the valve seat.

At high speeds, the limit of the second stage discs phases into the third stage orifice restrictions. Compression control, then, is the force that results from a higher pressure present in chamber B, which acts on the bottom of the piston and the piston rod area.

Extension cycle As the piston and rod move upward toward the top of the pressure tube, the volume of chamber A is reduced and thus is at a higher pressure than chamber B. Because of this higher pressure, fluid flows down through the piston's 3-stage extension valve into chamber B.

However, the piston rod volume has been withdrawn from chamber B greatly increasing its volume. Thus the volume of fluid from chamber A is insufficient to fill chamber B. The pressure in the reserve tube is now greater than that in chamber B, forcing the compression intake valve to unseat. Fluid then flows from the reserve tube into chamber B, keeping the pressure tube full.

Extension control is a force present as a result of the higher pressure in chamber A, acting on the topside of the piston area.

Shock Absorber Design

There are several shock absorber designs in use today:

  • Twin Tube Designs
    • Gas Charged
    • PSD
    • ASD
  • Mono-Tube

Basic Twin Tube Design The twin tube design has an inner tube known as the working or pressure tube and an outer tube known as the reserve tube. The outer tube is used to store excess hydraulic fluid.

There are many types of shock absorber mounts used today. Most of these use rubber bushings between the shock absorber and the frame or suspension to reduce transmitted road noise and suspension vibration. The rubber bushings are flexible to allow movement during suspension travel. The upper mount of the shock absorber connects to the vehicle frame.

Notice that the piston rod passes through a rod guide and a seal at the upper end of the pressure tube. The rod guide keeps the rod in line with the pressure tube and allows the piston to move freely inside. The seal keeps the hydraulic oil inside and contamination out.

The base valve located at the bottom of the pressure tube is called a compression valve. It controls fluid movement during the compression cycle.

Bore size is the diameter of the piston and the inside of the pressure tube. Generally, the larger the unit, the higher the potential control levels because of the larger piston displacement and pressure areas. The larger the piston area, the lower the internal operating pressure and temperatures. This provides higher damping capabilities.

Ride engineers select valving values for a particular vehicle to achieve optimal ride characteristics of balance and stability under a wide variety of driving conditions. Their selection of valve springs and orifices control fluid flow within the unit, which determines the feel and handling of the vehicle.

Twin Tube - Gas Charged Design The development of gas charged shock absorbers was a major advance in ride control technology. This advance solved many ride control problems which occurred due to an increasing number of vehicles using uni-body construction, shorter wheelbases and increased use of higher tire pressures.

The design of twin tube gas charged shock absorbers solves many of today's ride control problems by adding a low pressure charge of nitrogen gas in the reserve tube. The pressure of the nitrogen in the reserve tube varies from 100 to 150 psi, depending on the amount of fluid in the reserve tube. The gas serves several important functions to improve the ride control characteristics of a shock.

The prime function of gas charging is to minimize aeration of the hydraulic fluid. The pressure of the nitrogen gas compresses air bubbles in the hydraulic fluid. This prevents the oil and air from mixing and creating foam. Foam affects performance because it can be compressed - fluid can not. With aeration reduced, the shock is able to react faster and more predictably, allowing for quicker response time and helping keep the tire firmly planted on the road surface.

An additional benefit of gas charging is that it creates a mild boost in spring rate to the vehicle. This does not mean that a gas charged shock would raise the vehicle up to correct ride height if the springs were sagging. It does help reduce body roll, sway, brake dive, and acceleration squat.

This mild boost in spring rate is also caused by the difference in the surface area above and below the piston. With greater surface area below the piston than above, more pressurized fluid is in contact with this surface. This is why a gas charged shock absorber will extend on its own.

The final important function of the gas charge is to allow engineers greater flexibility in valving design. In the past such factors as damping and aeration forced compromises in design.

  • Improves handling by reducing roll, sway and dive
  • Reduces aeration offering a greater range of control over a wider variety of road conditions as compared to non-gas units
  • Reduced fade - shocks can lose damping capability as they heat up during use. Gas charged shocks could cut this loss of performance, called fade
  • Can only be mounted in one direction
Current Uses:
  • Original equipment on many domestic passenger car, SUV and light truck applications

Twin Tube - PSD Design In our earlier discussion of hydraulic shock absorbers we discussed that in the past, ride engineers had to compromise between soft valving and firm valving. With soft valving, the fluid flows more easily. The result is a smoother ride, but with poor handling and a lot of roll/sway. When valving is firm, fluid flows less easily. Handling is improved, but the ride can become harsh.

With the advent of gas charging, ride engineers were able to open up the orifice controls of these valves and improve the balance between comfort and control capabilities available in traditional velocity sensitive dampers.

A leap beyond fluid velocity control is an advanced technology that takes into account the position of the valve within the pressure tube. This is called Position Sensitive Damping (PSD).

The key to this innovation is precision tapered grooves in the pressure tube. Every application is individually tuned, tailoring the length, depth, and taper of these grooves to ensure optimal ride comfort and added control. This in essence creates two zones within the pressure tube.

The first zone, the comfort zone, is where normal driving takes place. In this zone the piston travel remains within the limits of the pressure tube's mid range. The tapered grooves allow hydraulic fluid to pass freely around and through the piston during its midrange travel. This action reduces resistance on the piston, assuring a smooth, comfortable ride.

The second zone, the control zone, is utilized during demanding driving situations. In this zone the piston travels out of the mid range area of the pressure tube and beyond the grooves. The entire fluid flow is directed through the piston valving for more control of the vehicle's suspension. The result is improved vehicle handling and better control without sacrificing ride comfort.


  • Allows ride engineers to move beyond simple velocity sensitive valving and use the position of the piston to fine tune the ride characteristic.
  • Adjusts more rapidly to changing road and weight conditions than standard shock absorbers
  • Two shocks into one - comfort and control


  • If vehicle ride height is not within manufacturer's specified range, piston travel may be limited to the control zone

Current Uses:

  • Primarily aftermarket under the Sensa-Trac brand name

Twin Tube - ASD Design

We have discussed the compromises made by ride engineers to bring comfort and control together into one shock absorber. This compromise has been significantly reduced by the advent of gas charging and position sensitive damping technology.

A new twist on the comfort/ control compromise is an innovative technology which provides greater control for handling while improving ride comfort called Acceleration Sensitive Damping (ASD).

This technology moves beyond traditional velocity sensitive damping to focus and address impact. This focus on impact is achieved by utilizing a new compression valve design. This compression valve is a mechanical closed loop system, which opens a bypass to fluid flow around the compression valve.

This new application specific design allows minute changes inside the pressure tube based on inputs received from the road. The compression valve will sense a bump in the road and automatically adjust the shock to absorb the impact, leaving the shock with greater control when it is needed.

Due to the nearly instantaneous adjustment to changes in the road's condition, vehicle weight transfer is better managed during braking and turning. This technology enhances driver control by reducing pitch during braking and roll during turns.


  • Control is enhanced without sacrificing driver comfort
  • Valve automatically adjusts to changes in the road condition
  • Reduces ride harshness


  • Limited availability

Current Uses:

  • Primarily aftermarket applications under the Reflex brand name.

Mono-Tube Design

These are high-pressure gas shocks with only one tube, the pressure tube. Inside the pressure tube there are two pistons: a dividing piston and a working piston. The working piston and rod are very similar to the twin tube shock design. The difference in actual application is that a mono-tube shock absorber can be mounted upside down or right side up and will work either way. In addition to its mounting flexibility, mono-tube shocks are a significant component, along with the spring, in supporting vehicle weight.

Another difference you may notice is that the mono-tube shock absorber does not have a base valve. Instead, all of the control during compression and extension takes place at the piston.

The pressure tube of the mono-tube design is larger than a twin tube design to accommodate for dead length. This however makes it difficult to apply this design to passenger cars designed OE with a twin tube design. A free-floating dividing piston travels in the lower end of the pressure tube, separating the gas charge and the oil.

The area below the dividing piston is pressurized to about 360 psi with nitrogen gas. This high gas pressure helps support some of the vehicle's weight. The oil is located in the area above the dividing piston.

During operation, the dividing piston moves up and down as the piston rod moves in and out of the shock absorber, keeping the pressure tube full all times.


  • Can be mounted upside down, reducing the unsprung weight
  • May run cooler since the working tube is exposed to the air


  • Difficult to apply to passenger cars designed OE with twin tube designs.
  • A dent in the pressure tube will destroy the unit

Current Uses:

  • Original equipment many import and performance domestic passenger cars, SUV and light truck applications
  • Available for many Aftermarket applications

Back to TopWhat is a Strut

Now that we have a more thorough understanding of shock design, let's focus on the strut. The strut is a common damper type used on many of today's independent suspension, front wheel drive vehicles as well as some rear wheel drive vehicles.

A strut is a major structural part of a suspension. It takes the place of the upper control arm and upper ball joint used in conventional suspensions. Because of its design, a strut is lighter and takes up less space than the shock absorbers in conventional suspension systems.

Struts perform two main jobs. First, struts perform a damping function like shock absorbers. Internally, a strut is similar to a shock absorber. A piston is attached to the end of the piston rod and works against hydraulic fluid to control spring and suspension movement. Just like shock absorbers, the valving generates resistance to forces created by the up and down motion of the suspension. Also like shock absorbers, a strut is velocity sensitive, meaning that it is valved so that the amount of resistance can increase or decrease depending on how fast the suspension moves.

Struts also perform a second job. Unlike shock absorbers, struts provide structural support for the vehicle suspension, support the spring, and hold the tire in an aligned position. Additionally, they bear much of the side load placed on the vehicle's suspension. As a result, struts affect riding comfort and handling as well as vehicle control, braking, steering, wheel alignment and wear on other suspension components, including tires.

Strut Components

Typically, struts consists of a coil spring to support the vehicle's weight, a strut housing to provide rigid structural support for the assembly, and a damping unit within the strut housing to control spring and suspension movement. The bottom of the strut body attaches to the steering knuckle, which in turn connects to a lower control arm through a lower ball joint.

The top of the strut is connected to the vehicle body through the upper strut mount, in some cases called a bearing plate. This bearing plate allows the strut to pivot as the wheels are turned. It must be flexible enough to handle slight angle changes and dampen movement of the upper end of the strut. This mount or bearing plate transfers vehicle load to the strut and spring, making the upper mount/bearing plate the load carrier and the lower ball joint the follower.

The strut housing holds the damping unit and fluid. It is made of heavy gauge steel so that it is rigid enough to provide structural support and withstand road shock.

The piston rod of the strut is much larger in diameter than the piston rod of the typical shock absorber. This is to withstand the side load on the strut shaft. A strut rod will measure up to 7/8 of an inch in diameter while the piston rod of a typical shock measures up to ½ of an inch in diameter.

A coil spring is located between the upper and lower spring seats. It is held there by tension. The lower spring seat is welded to the strut housing, while the upper spring seat is kept in place by the upper strut mount.

Struts also have a jounce (or compression) bumper located under the upper spring seat. The purpose of this component is to limit suspension travel by not allowing suspension components to hit together.

Finally, a large nut at the end of the strut rod holds everything together.


  • Aftermarket: A replacement part that is produced and sold by a company other than the original manufacturer.
  • Air Suspension: A system in which air-filled, elastic springs are used in place of metallic springs.
  • Alignment Angles: Camber, caster, toe, turning radius, and steering axis inclination. All these angles must be set correctly to ensure proper handling and tire wear.
  • Alignment: The process of adjusting the position of the tires and steering axis to bring them to a specified predetermined position.
  • Axis: A line or point marking the center of rotation of an object or thing.
  • Axle: A cross support that is designed to carry the weight of the car.


  • Balance, Chassis: A ride condition that gives a level and flat front-to-rear flowing sensation without pitch.
  • Balance, Tire: A condition in which the tire can spin without causing a vibration of the suspension or car.
  • Ball Joint: A connector consisting of a ball and socket. This configuration allows for angular and rotating motion at the same time.
  • Bearing: A device that allows rotation or linear motion with a minimum of friction. It usually uses a series of balls or rollers so there is a rotating motion of the internal parts.
  • Bellows: A flexible, accordion-like seal used where angular or lateral motions require a large degree of movement.
  • Bottoming: A noise and jolt created when the compression cycle of the suspension ends at the bump stops.
  • Bounce: Straight-line motions of the sprung mass of a car in a vertical direction.
  • Bump Steer: A directional change in steering caused by road surface irregularities. As the suspension moves through jounce and rebound, changes in alignment at the front or rear wheels may alter the vehicle's path.
  • Bump Stop: An elastic member which increases the spring rate near the end of the compression and extension travel to reduce the effects of bottoming and/or topping.
  • Bushing: A component made from a variety of natural and synthetic materials, used to locate or guide interconnected moving parts.


  • Camber: The inward or outward tilt of the wheel as measured in degrees. If a tire tilts inward toward the vehicle, it has negative camber. If the tire tilts outward away from the vehicle, it has positive camber.
  • Caster: The amount, in degrees, that the steering axis is tilted from true vertical backward or forward viewed from the side of the vehicle.
  • Center Link: A tube or rod used as a connection between the pitman arm and idler arm, and connected to the inner tie rod assemblies. Normally used on cars and light trucks.
  • Centrifugal Force: A force acting on a turning body that pushes the body outward.
  • Chassis: The portions of a car that remain after the body has been removed. It includes suspension and steering systems.
  • Center of Gravity, CG: The balance point of a car.
  • Coefficient of Friction: The amount of friction there is between two items that is dependent on the composition of the two materials.
  • Coil Spring: A spring steel wire in the shape of a coil used as the springing medium for the suspension.
  • Compliance: The ability to yield elastically to change position.
  • Computer Controlled Suspension: A suspension system which uses a computer to change the shock absorber settings and/or air spring pressure to suit various driving conditions.
  • Control Arm: A suspension member used to determine the position of a steering knuckle or axle, usually in a lateral direction.
  • Cornering Force: The traction force in a lateral direction that is generated by a tire.


  • Damped, Dampened: A force or action opposing a vibrating motion to reduce the amount of vibration.
  • Deflection: A movement that changes shape or position reacting to an outside force.
  • Directional Stability: Ability of a car to travel in a straight line with a minimum of correction from the driver.
  • Dive: A pitching motion of the sprung mass of a car downward at the front, which usually occurs during braking.
  • Drag Link: A tube or rod used as connection between the pitman arm and steering knuckle. Normally used on cars and light trucks.
  • Dry Park Check: An undercar inspection method performed with full vehicle weight on all tires. The steering wheel is turned left and right while the technician visually inspects the steering and suspension components.
  • Dynamic Balance: A balancing of the lateral, centrifugal forces of a spinning tire and wheel.


  • Eccentric Cam: washers with a hole off-center so it does not rotate in a perfect circle. Normally used to adjust camber and/or caster.


  • Feather Edge: An abnormal tire wear condition in which each tire rib wears in a tapered, angled fashion.
  • Float: A slow, low frequency movement of the car which produces a sensation of continuous front-to- rear, vertical movement of the suspension.
  • Force: Physical power that will cause movement.
  • Frame: The structural load carrying member that supports a car's engine and body, which in turn are supported by the suspension and wheels.
  • Frequency: The speed at which an action occurs.
  • Full Contact Shims: Shims used to correct alignment problems. Normally used on front-wheel drive vehicles with a straight rear axle.

G - H

  • G Force, g: A measurement of the amount of acceleration, braking, or cornering force that a car can generate.
  • Handling: The relative ability of a vehicle to maneuver through turns and go where the driver wants it to go.
  • Harshness: Vibrations that can be felt and/or heard that are caused by interaction between the tire and the road surface. It can be caused by tire or road irregularities.
  • Hop: The vertical oscillations of a tire that can be caused by static or kinetic unbalance.
  • Hub: The assembly that houses the bearings around which the wheel and tire assembly rotates.


  • Idler Arm: An arm and lever assembly used to support and maintain a parallel position with a conventional steering system.
  • Independent Front Suspension (IFS): Suspension using two frame mounted control arms at each of the front wheels. Lets each wheel respond individually to bumps and dips in the road.
  • Inner Tie Rod Socket: The pre-assembled unit that becomes the inner tie rod end. Used only on rack and pinion steering systems.

J - L

  • Jounce: A bounce motion during which the tire travels upward, relative to the car, compressing the spring and shock absorber.
  • King Bolt, KingPin: A sturdy steel shaft used to connect the steering knuckle to an axle. It provides the pivot axis.
  • Lateral: A direction that is to the side.
  • Linkage: A system of levers and rods used to transmit motion or force.
  • Load Range: A system of measuring and labeling the carrying capacity of the tires.

M - O

  • MacPherson Strut: See Strut.
  • OEM, Original Equipment Manufacturer: The company that made the parts that were originally used on a car.
  • Oscillation: A back-and-forth, repeating motion.


  • Pinion Housing: The portion of the rack and pinion unit that houses the spool valve and torsion bar.
  • Pitch: Rotary motions of the sprung mass of a car around the transverse axis. The front end will rise while the rear lowers and vice versa.
  • Pitman Arm: A steering component that provides interconnection between the steering gear sector shaft and the steering linkage.
  • Play: Free movement of an item allowed by internal clearances.
  • Pressure: A unit of force applied on a given area.
  • Pull: A tendency for a car to steer toward one side.


  • Radius Arm: A type of control arm that attaches to an axle at one end and pivots at the other end. It is often mounted in a lengthwise direction.
  • Rebound: A bounce motion during which the tire travels downward relative to the car and the spring and shock absorber extend.
  • Returnability: The tendency of the front wheels to return to a straight-ahead position.
  • Ride Control: Achieving the objectives of the suspension while a vehicle is in motion.
  • Ride Height: The distance from a specific point on a vehicle to level ground. The actual measurement should be equal to vehicle specifications before correcting alignment.
  • Road Shock: A harsh force transmitted from the tires through the suspension or steering linkage.
  • Roll Rate: The amount of resistance generated by the suspension components that resist roll.
  • Roll: A rotary motion of the sprung mass of a car around the longitudinal (lengthwise) axis that results in body roll.
  • Roughness: A heard or felt vibration generated by a rolling tire on a smooth road surface that produces the sensation of rolling on a course or irregular road surface.


  • Seal: A flexible rubber or synthetic material used to keep lubrication in and contaminants out of a specific area.
  • Shim: A thin material, fiber or metallic spacer used to adjust the distance or angle of an item.
  • Shimmy: A violent shake of the front wheels transmitted up to the steering wheel.
  • Shock Absorber: A device, usually hydraulic, used to dampen or reduce the amount of spring oscillation after a bump.
  • Short/Long Arm (SLA): An independent suspension design that incorporates unequal length control arms.
  • Skid: A sliding rather than a rolling action of the tire across the road.
  • Solid Axle Suspension: A suspension system consisting of one steel or aluminum 1-bearn extending the width of the vehicle.
  • Spring Rate: The change of load on a spring per unit of deflection.
  • Spring: A flexible suspension member, which allows bounce travel of the suspension.
  • Sprung Weight: The total weight of the portions of the car, which are carried by the springs.
  • Squat: A pitching motion of the sprung mass down ward at the rear that often occurs during acceleration.
  • Stability: The tendency of a vehicle to maintain a directed course.
  • Steering Knuckle: The front suspension component that attaches the front tire and wheel to the steering axis and steering linkage.
  • Steering System: The entire mechanism that allows the driver to guide and direct a vehicle.
  • Strut Rod: A suspension member that is used to brace the control arm to keep it from moving forward or backward.
  • Strut Suspension: A suspension design in which spindle, shock, and spring are all one assembly.
  • Strut: A suspension system type that utilizes the shock absorber as the upper tire position locating member.
  • Suspension: An assembly used to support weight, absorb and dampen shock, and help maintain tire contact and proper wheel-to-chassis relationships.


  • Tie Rod Assemblies: The outermost assemblies on a parallelogram steering linkage. These assemblies are attached to the drag link and steering arms.
  • Tie Rod End: The ball and socket assembly of a tie rod.
  • Tire Contact Area, Tire Print: The amount of tire tread that is in contact with the road surface. Also called the "footprint."
  • Toe: The difference in distance between the front and back of corresponding tires.
  • Toe In: A condition where both tires of an axle are positioned so they are closer together at the front than the rear.
  • Toe Out: A condition where both tires of an axis are positioned so they are closer together at the rear than the front.
  • Topping: A noise and jolt when the extension cycle of the suspension travel ends at the bump stop.
  • Torque: A twisting or turning force.
  • Torsion Bar: A spring that allows suspension motion by twisting.
  • Torsion: A rotating motion that causes a twisting action.
  • Track: The center-to-center distance between the two tires on an axle.
  • Tracking: The degree in which the rear tires follow behind the front tires.
  • Traction: The ability of a tire to grip the road surface.
  • Transverse: A direction that goes across a car.
  • Tread Width: The outside-edge-to-outside-edge width of the two tires on an axle.


  • Unsprung Weight: The weight of vehicle components not supported by the springs. Parts included are the wheels, tires, rear axle (but not always the differential), steering linkage, and some suspension parts.
  • Variable Rate Coil Springs: Springs used to provide additional load bearing capacity for cars and light trucks. Unlike a standard coil spring, the coils of variable rate springs are not equally spaced. The bottom coils are more widely spaced than those at the top, which allows them to provide extra support when needed.
  • Vertical Movement: The up-and-down movement of the ball joint or tie rod end.
  • Vibration: A periodic motion or oscillation of an item that often causes an annoying motion or sound.
  • Wander, Weave: The tendency of a car not to follow a straight line; it requires continuous correction from the driver.
  • Weight Transfer: The amount of weight that moves laterally because of cornering forces or lengthwise, because of acceleration or braking forces.
  • Wheel Hop: A rapid vertical oscillation of the tires resulting from a loss of traction control.
  • Wheelbase: The center-to-center distance between the front and rear tires.
  • Yaw: The rotary motion of the sprung mass of a car around a vertical axis that is encountered in a spin.
Part # Description
20-65225 TJ Rear Pinion Adjustment Cams
20-66823 TJ Shifter Drop
90-3242 Super Duty Rear Shock Bracket
90-6064 Sway Bar Extension 8 Lug 4WD GM
90-6100 4" Sway Bar Kit GM
90-6102 GM 2 Bolt Idler Arm Spacer Kit
90-6170 CAM Bolt Assembly
90-6275 99-06 GM 1500 Upper Control Arm Shim Kit for 51099 Kit
90-6410 Titan Cam Bolt Assmebly
90-6428 Super Duty Double Shock Hoop Sleeves & Bushings
90-6432 2006 Chevy Rear Shock Bracket Kit with Ride Control
90-6438 Spare Tire Guide Bracket Installation Kit
532 Camber&Caster Adjustable bushing 83-94 4x4 Ford Full Size Trucks
535 Camber&Caster Adjustable Bushing 80-92 4x4 Ford Downsize Trucks
594 Camber & Caster Eccentric Adjusters for I-Beam 2WD Ford 99-04 Super Duty/ 90-96 F150/ 89-97 Ranger
2502 Steering Stabilizer 82-83 2WD Mitsubishi PickUp & 79-95 2WD Toyota PickUP
2504 Toyota Steering Stabilizer
2508 Single Stabilizer Brackets for Early Domestic Light truck and Jeep to 1975, Import trucks
2509 Steering Stabilizer Application for various Jeeps and Scouts
2512 Single Stabilizer Brackets for Dana 60 Axle with 3.5 inch OD
2513 Ford Ranger 2WD & 4WD
2516 Application for 71-82 2WD Chevy&GMC G10, G15, G20, G25
2517 Application for 71-78 2WD Dodge-Plymouth B100, B200, B300
2520 Stabilizer brackets for 55-84 Toyota FJ
2522 Single Stabilizer Brackets for 1980 Ford 2WD F Series
2525 Steering Stabilizer 79-83 4WD Toyota Pickups & 84-85 4WD Toyota Pickups
2537 Steering Stabilizer 2WD&4WD F150/ F250/ Bronco/ Bronco II/ Ranger
2551 Single Stabilizer Brackets for 80-89 Nissan Patrol
2552 Single Stabilizer brackets for 89-94 Nissan Patrol
2561 Dual Steering Stabilizer Application for models of Chevy, Dodge, & Ford
2562 Toyota 4x4 Dual Stabilizer
2563 Ford F150, Bronco Kits
2580 Steering Stabilizer 97-03 F150 4x4 & Expedition 4x4
2585 99-2001 2WD Ford Super Duty F250&F350 & Excursion Steering Stabilizer
2600 Chevy-GMC Steering Stabilizer Mount Kit
2770 Super Duty 99-04 4WD Trucks & Excursion
4040 Jeep YJ Driveshafts
4041 Jeep YJ Driveshafts
5400 Universal Limit Strap
7000 Brakeline
10000 Univeral Light Bar
11400 Front Bumper 76-04 Jeep CJ Wrangler YJ-TJ
12400 Front Bumper 76-04 Jeep CJ Wrangler YJ-TJ
14400 Front Bumper 76-04 Jeep CJ Wrangler YJ-TJ
15400 Front Bumper 76-04 Jeep CJ Wrangler YJ-TJ
17400 Front Bumper 76-04 Jeep CJ Wrangler YJ-TJ
12000 92-96Ford Full Size Pick Up, Bronco Light Bar
13129 2005-2006 Toyota Tacoma 4WD-2WD Pre-Runner Add-A-Leaf
13134 2004 F150 Add-A-Leaf Kit
16000 93-96 Ford Ranger Light Bar
17000 Toyota 4WD Light Bar
21000 GMC-Chevy HD Half & Three Quarter Ton 2x4 and 4x4 Light Bar
21200 GMC-Chevy HD Half & Three Quarter Ton 2x4 and 4x4 Light Bar
21300 GMC-Chevy HD Half & Three Quarter Ton 2x4 and 4x4 Light Bar
21400 Light Bar Kit Socket-Socket Style
22000 Light Bar Kit Socket-Socket Style
22400 Rear Bumper 76-02 Jeep CJ, Wrangler YJ-TJ
23400 Rear Bumper 76-02 Jeep CJ, Wrangler YJ-TJ
23700 Jeep JK Light Bar
24020 Light Bar Kit Socket-Socket Style
24500 Light Bar Kit Socket-Socket Style
24600 Light Bar Kit Socket-Socket Style
25000 Tacoma Light Bar
25400 Rear Bumper 76-02 Jeep CJ, Wrangler YJ-TJ
27400 Rear Bumper 76-02 Jeep CJ, Wrangler YJ-TJ
24400 Light Bar Kit F250-F350 Super Duty
24500 Ford Super Duty Light Bar Kit
26100 02-04 Dodge 1500 Light Bar
27000 Nissan Light Bar
41315 79-85 Toyota 4WD PickUp 4" Front Kit
51007B 07 GM Silverado 4WD without Driveshaft
51017B 07 GM Silverado 4WD with Driveshaft
51020MX-1 Lower Control Arm Shims for 99-06 GM1500 4WD with 51020BMX kit
51020MX 99-03 Silverado 5 inch Lift Kit
51021 6" Lift 02-03 Chevy/GMC/Tahoe/Yukon,4x4 with Electronic Ride Control Option
51022 6" Lift Chevy/ GMC/ Tahoe/ Yukon 4x4 without Electronic Ride Control Option
51023 6" Lift 00-06 Chevy/ GMC/ Tahoe/ Yukon/ Avalanche 2WD Suspension Lift with A-Arm Drops with Electronic Ride Control Option
51024MX 01-06 2WD Tahoe/ Yukon/Yukon XL/ Avalanche 5" Lift Kit
51028 00-06 Chevy/ GMC/ Tahoe/ Yukon/ A-Arm Drops with Electronic Ride Control Option
51050 01-03 2WD Tahoe/ Yukon/ Yukon XL/ Avalanche (rear installation supplement for 51022&51024MX)
51051 1500 GM Electronic Shock Adapter Kit For kits 51099 & 51011 only
51080 99-06 Chevy Silverado 2WD 7" Lift Kit
51080MX 99-06 Chevy Silverado 2WD 7" Lift Kit
51084 04-06 Chevy/ GMC 1500 Crew Cab 2WD 7" lift with Coil Spring front end
51084MX 04-06 Chevy/ GMC 1500 Crew Cab 2WD 7" lift with Coil Spring front end
51086MX 05-06 2WD Chevy Silverado with Torsion Bars 6" Lift Kit
51088 88-98 Chevy/ GMC 4WD Half Ton Pickup (6 lug) 6" IFS Non Autotrac Current Production
51092 88-99 Chevy/ GMC 4WD Half Ton Pickup (6 lug) 6" IFS Early Production
51093 88-99 Chevy/ GMC 4WD Half Ton Pickup (6 lug) 6" IFS Early Production
51094 88-99 Chevy/ GMC 4WD Half Ton Pickup (6 lug) 6" IFS Early Production
51095 Yukon/ Tahoe Upgrade Kit
51098 Chevy/ GMC 4WD Half Ton Pickup/ Tahoe/ Surburban (6 Lug) 6" IFS
51099 Chevy/ GMC 4WD HalfTon 4x4 99-06 Silverado/ Sierra
51099B 99-07 GM 1500 "Classic body" 6" Suspension
51103 Skid Plate 2WD GM 99-06
51188 88-99 GM Skidplate for Early Production Kit 6" Kit
51190 Skid Plate for discontinued 4" 51492, 51493 Lift Kit 88-98 GM1500
51196 88-99 GM 1500 Skid Plate for Current Production 6" kit
51199 99-06 GM 1500 4WD/ 2WD Skid Plate for 6" lift
51210 Multiple Shock Hoop Kit 01-06 GM 8 Lug HD
51255 99-06 GM/ 03-06 Dodge Carrier Bearing Alignment Kit
51288 88-93 6 Lug Triple Shock Hoop system with Crossover Brace
51292 88-98 Chevy/ GMC 2WD 6" Lift Kit
51294 88-99 GM 1500 Double Shock Hoop 4" and 6" lift
51295 88-99 GM 1500 Double Shock Hoop with shocks for 6" lift
51297 Shock Hoop Chevy/Gmc Half Ton 4x4 99-06 Silverado/ Sierra
51299 Shock hoop Chevy/GMC Half Ton 4x4 99-04 Silverado/ Sierra
51315 79-85 Toyota 4WD Pickup & 4 Runner Front Kit
51494 88-98 Chevy/GMC Half Ton 4x4 4" Suspension Syetem
51800 6" Lift kit 00-06 Chevy/ GMC 3/4 ton 4x4
51800B 00-07 GM 2500 / 2500HD / 1500HD 6" Suspension
51893 Chevy/GMC 4WD 3/4 ton (8 lug) IFS 88-99 6" Lift
51894 Chevy/GMC 4WD 3/4 ton (8 lug) IFS 88-99 6" Lift
51907B 07 GM Tahoe 4WD with Driveshaft
51927B 07 GM Tahoe 4WD with Driveshaft
51947B 07 GM Tahoe 4WD without Driveshaft
52080 Ford F150 IFS Stage II Suspension System
52097 4" Suspension System 97-03 Ford Full Size 4WD IFS F150-F250
52098 97-03 Ford Full Size 4WD IFS F150-F250 4" Suspension System
52100 97-03 2WD Ford F150 Skid Plate
52102 04-06 2WD Ford F150 Skid Plate
52104 2004 4WD Ford F150 Skid Plate
52180 82-96 Ford F150 & Bronco IFS Stage I Suspension System
52189 83-95 Ford Ranger Skid Plate
52197 97-98 Ford 4WD Front Skid Plate Kit
52203 97-03 Ford F150 2WD 6" Lift Kit
52204 04-06 Ford F150 4WD
52204B 04-07 Ford F150 6" Suspension System
52204MX 04-06 Ford F150 4WD
52205 04-06 Ford F150 2WD
52205MX 04-06 Ford F150 2WD
52206MX 2004 Ford F150 4WD Coil Upgrade Kit For the Procomp 52204 Kit
52207MX 2004 Ford F150 2WD Coil Upgrade Kit For the Procomp 52205 Kit
52209B 2009-UP Ford F150 4WD Suspension
52209BMX 2009-UP Ford F150 4WD Suspension
52210 April 99 to 2004 Ford 4WD Super Duty F250/F350
52211BMX 2009-UP Ford F150 4WD Upgrade Kit for 52209 Suspension
52212 05-06 Ford Super Duty 4WD F250-350 2" Leveling kit
52212B 05-07 Ford F250/ F350 4WD 2” Suspension
52212BMX 05-07 Ford F250/ F350 4WD 2” Suspension
52213B 2009-UP Ford F150 2WD 6” Suspension
52213BMX 2009-UP Ford F150 2WD 6” Suspension
52214BMX 2009-UP Ford F150 2WD Upgrade Kit for 52213 Suspension
52246 99-06 GM Fixed Yoke Conversion with CU Driveshaft
52289 86-96 Ford Ranger 2WD IFS Stage 1 Suspension System
52410 Ford SuperDuty 4x4 Fornt Double Shock Bracket
52412 Up to 4-99 Production Date Ford 4WD SuperDuty F250/ F350
52413 Ford Super Duty 4WD F250-350 Stage 1 Lift Kit with Add-A-Leaf
52414 99-04 Ford 4WD Super Duty 250-350
52415 05-06 Ford Super Duty 4WD F250-350 Stage 2 Lift Kit with Add-A-Leaf
52416 00-04 Ford 4WDSuper Duty 250/Excursion
52417 05-06 Ford Super Duty 4WD F250-350 Stage 2 Lift Kit
52418 99-04 Ford 4x4 Super Duty F20-350 6.5" Lift
52418MX 99-04 Ford 4x4 Super Duty F20-350 6.5" Lift
52419 99-04 Ford 4x4 Super Duty F250-350 8.5" Lift
52419MX 99-04 Ford 4x4 Super Duty F250-350 8.5" Lift
52420 99-04 Ford Super Duty/ Excursion 4WD with Hoop kit
52421 05-06 Ford Super Duty 4WD F250-350 Stage 1 Lift Kit
52423 05-06 Ford Super Duty 4WD F250-350 Stage 1 Lift Kit with Add-A-Leaf
52423MX 05-06 Ford Super Duty 4WD F250-350 Stage 1 Lift Kit with Add-A-Leaf
52432BMXR 05-07 Ford F250 6" XX Coil Over conversion
52434BMXR 05-07 Ford F250 6" XX Coil Over conversion
52438BMXR 05-07 Ford F250 8" XX Coil Over conversion upgrade
52440 05-06 Ford Super Duty 4WD Double Shock Hoop Kit
52450 05-06 Ford Super Duty 4WD Double Shock Hoop Kit
52480 Ford Super Duty F250-350 4WD Driveshaft Kit
52482 99-04 Ford Super Duty F250-350 2" Hanger Leveling kit
52483 Crash Bar with Spring Hanger Reinforcement Tube
52484 99-04 Ford 4x4 Super Duty F250-350 add on for 6.5" lift kit
52513 Ford Super Duty 4WD F250-350 Stage 1 Lift Kit with Leaf Springs
52515 05-06 Ford Super Duty 4WD F250-350 Stage 2 Lift kit with Leaf Springs
52612 99-04 Super Duty 2WD F250-350
52614 00-04 2WD Excursion
52616 00-04 4WD Ford Excursion 4" or 6"
52700 04-06 Ford F150 Rear End Shims
52800B 2008 Ford Super Duty 6" Stage 1
52801B 2008 Ford Super Duty 6" Stage 2
52820B 2008 Ford Super Duty 2"
52860B 08-09 Ford F250/F350 4WD Stage I 6” Suspension
55060 76-86 Jeep CJ Steering Box Brace
55070 87-95 YJ Wrangler Steering Box Brace
55076 Transfer Case Lowering Kit 76-86 CJ-5/ CJ-7 Jeep
55089 86-96 Jeep Wrangler 2.5" or 4" Suspension Lift
55095 Stainless Steel Toe Ring Jeep YJ
55099 87-95 YJ/Wrangler Coil Spring Suspension
55300 97-06 Jeep TJ Front Track Bar Drop
55500 97-06 Jeep TJ Steering Box Skidplate
55506 97-06 Jeep TJ Sway Bar Disconnect
55297 Jeep Wrangler TJ 1.5-2.0 Replacement Coil Kit
55298 Jeep Wrangler TJ 1.5-2.0 Replacement Coil Kit
55299 97-02 Jeep Wrangler TJ Rear Track Bar Bracket
55415 Jeep Wrangler TJ 1.5 Spacer Kit
55495 97-02 4WD Jeep Wrangler TJ "Stage 1" 3" to 4" lift Manufactured with Chromolly Arms
55499 97-02 4WD Jeep Wrangler TJ "Stage 2" 3" to 4" lift designed to fit vehicles with Power Steering Manufactured with Chromolly Arms
55499RH Right Hand Drive TJ Rear Track Rod Bracket
55589 Transfer Case Drop Kit
55590 84-01 4WD & 2WD Jeep XJ Cherokee 3" lift with manufactured chromolly arms
55591 92-98 Jeep Grand Cherokee/Wagoneer 4WD 3" lift with Manufactured Chromolly Arms
55597 XJ/ZJ Front Sway Bar Links
55695 03-04 4WD Jeep Wrangler TJ "Stage 1" 3" to 4"
55699B 97-06 Jeep TJ Stage II box kit
55707B 2007 Jeep JK 4"/ 2" Suspension system
55717B 2007 Jeep JK 4" box kit
55727B 2007 Jeep JK 4" Stage II boxkit
56001 Add A Leaf
56094 94-00 Dodge 4WD 1/2 ton 3" kit
56194 94-00 Dodge 4WD 3/4 ton 2" kit
56294 94-00 Dodge 4WD 1/2 ton 3" kit Stage 2
56394 94-00 Dodge 4WD 3/4 ton 2" kit Stage 2
56494 94-00 Dodge 4WD 1/2 ton 3" kit
56594 94-00 Dodge 4WD 3/4 ton 2" kit
56701 94-05 Dodge 1500 4WD Index Ring Kit
56702MX 02-04 Dodge IFS 1/2 ton 4x4 5" lift
56703MX 03-06 Dodge 2500 1500 Mega Cab 4x4 3" lift
56705 03-06 Dodge 2500 4x4 5" lift
56705MX 03-06 Dodge 2500 4x4 5" lift
56746B 06-07 Dodge 4x4 1500 6" Suspension System
57001 Coil Spring
57007B 2007 Toyota FJ Cruiser 6" Suspension
57047 2007 Toyota Tundra 6" Stage I Suspension
57047MX 2007 Toyota Tundra 6" Stage II Suspension
57089 86-95 Toyota 4WD 4"
57093 Toyota T-100 4WD IFS 4"
57094 Toyota T-100 4WD IFS 4"
57095 Toyota Tacoma 4WD IFS 4"
57096 05-06 Toyota Tacoma 4WD-2WD Pre Runner
57096B 05-07 Toyata Tacoma 6" Suspension System
57096MX 05-06 Toyota Tacoma 4WD-2WD Pre Runner
57097MX 05-06 Toyota Tacoma 4WD-2WD Pre Runner Coil Upgrade Kit for Procomp Kit 57096
57190 Toyota 4WD Skid Plate
57195 Toyota Tacoma 4WD Skid Plate
57289 86-95 Toyota 4WD IFS Stage 2
57295 96-03 Toyota Tacoma 4WD 4" Lift Coilover Front Shocks
57396 07-09 Toyota Tacoma with VSC 4WD-2WD Pre Runner
57396MX 07-09 Toyota Tacoma with VSC 4WD-2WD Pre Runner
57489 90-95 Toyota 4 Runner Rear Suspension Kit
58000 U Bolt Kit
58001 U Bolt Kit
58103 73-87 GM 4WD Front Double Shock Kit
59000 Rear Block Kit
59001 04-06 Nissan Titan 6" 4WD
59001MX 04-06 Nissan Titan 6" 4WD
59002MX 04-06 Nissan Titan 4WD-2WD Coil Upgrade kit for Procomp kits 59001-59004
59003B Nissan Titan 2WD Carrier Bearing Spacer kit
59004 04-06 Nissan Titan 2WD
59004MX 04-06 Nissan Titan 2WD
59005 04-06 Nissan Armada 2WD-4WD
59005MX 04-06 Nissan Armada 2WD-4WD
59006MX 04-06 Nissan Armada 2WD-4WD (without auto ride) Coil Upgrade Kit for the Procomp 59005 kit
59007 04-06 Nissan Armada 2WD-4WD with Air Ride
59007MX 04-06 Nissan Armada 2WD-4WD with Air Ride
59008MX 04-06 Nissan Armada 2WD-4WD (with auto ride) Coil upgrade kit for the Procomp 59007 kit
64101 97-05 Jeep TJ 2" lift
64105 2007 Jeep JK Front & Rear leveling kit 1.75"
64201 03-05 Ford Expedition & 04-06 Ford F150 Front Coil Spring Spacer Kit
64202 Ford 2005 Super Duty Front Coil Spring Space Lift Kit
64301 95-03 Toyota 2.5" lift kit 6 lug 4WD-2WD Pre Runner Spacer Kit
64401 Dodge Coil Spacer Kit (Fits 94-01 1500 & 02-04 2500-3500)
64501 04-06 Nissan Titan, Armada 2WD & 4WD 2" Lift Spacer kit
66163 Rear Hitch Bumper Fits 76-86 Jeep CJ
66164 Front Bumper fits 76-99 Jeep CJ Wrangler/ YJ/ TJ
66165 Rear Hitch Bumper Fits 87-99 Jeep/ YJ/ TJ
71082 Lateral Trac Bar Mount Kit
71182 Lateral Trac Bar Mount Kit
7119 Lateral Traction Bar Mount Kit
72084 Lateral Traction Bar Mount Kit
71200 Track Bar Kit 01-02 Chevy, GMC 4x4 HD 3/4 ton
72082 Lateral Trac Bar Mount Kit
72090 F150 Traction Bar
72095 Traction Bar Kit 04-05 Ford F150 4WD Extra Cab
72096 Traction Bar Kit 04-05 Ford F150 Super Crew Cab 2WD & 4WD
72099 99-06 Super Duty Lateral Traction Bar Mounting Kit
77082 Lateral Trac Bar Mount Kit
77182 Rear Traction Bar Kit 96-01 Tacoma ( to be used with lift block ONLY)
79090B Traction Bar Kit 04 Nissan Titan 4WD (crew cab)
81088 88-98 Chevy, GMC 4WD IFS Rear Shock Mount System
81099 Rear Multi Shock Kit Chevy, GMC 1/2 4x4 99-01 Silverado/Sierra
87089 Shock Mount System for Toyota 4WD Lateral Trac Bar
217513 88-98 1/2 Chevy 4WD Steering Stabilizer Kit
218538 04-06 Ford F150 4WD-2WD Dual Steering Stabilizer Kit
218568 99-06 GM 2WD Steering Stabilizer
219201 Steering Stabilizer Kit
219567 05 4WD Ford Super Duty F250-F350 Dual Steering Stabilizer
220595 97-03 Ford F150 2WD Steering Stabilizer (non-lifted and lifted)(also, 2004 F150 heritage)
222570 99-04 4WD Super Duty and Excursion
222585-1 99-01 2WD Ford Super Duty F250-F350 & Excursion
222585 99-01 2WD Ford Super Duty F250-F350 & Excursion
227010 05 4WD Ford Super Duty F250-F350 Factory Replacement Steering Stabilizer
690001 Stem Mount to Eyelet Shock Adapter
690002 Stem Mount to Eyelet Shock Adapter
BF 08-09 Ford F250/F350 4WD Stage I 6” Suspension
BFR 08-09 Ford F250/F350 4WD Stage I 6” Suspension
BMX 08-09 Ford F250/F350 4WD Stage I 6” Suspension
BMXR 08-09 Ford F250/F350 4WD Stage I 6” Suspension
CAM BOLTS INST for General Cam Bolts
GDL40 GM Adjustable Dropped Drag Link
GM400 GM400 Steering Arm
GTA 1051 6" Lift Kit 00-05 Chevy/ GMC 3/4 ton 4x4
GTA 1095 99-03 Silverado 5" lift kit
GTA 1095 99-03 Silverado 5" lift kit
GTA 1136 88-98 Chevy/GMC 4WD 1/2 pick up ( 6 lug) 6 inch IFS nonauto trac)
INST-599 05 Ford Super Duty F250& F350 4WD
JTB400 Jeep Adjustable Track Bar Kit
JTB401 97-06 Jeep TJ Rear track bar
JTB402 2007 Jeep JK Front Adjustable track bar
JTB403 97-06 Jeep TJ Front track bar (Dana 44)
Right Hand Drive Right Hand Drive TJ Rear Track Rod Bracket
TJ3FL TJ Front Sway Bar Extensions
TJ R pinion TJ Rear Asjustment CAMS
TJF 600 Jeep TJ Frame Brace Kit
P-843 TJ Steering Stabilizer Mount
TOY400 Adjustable Dropped Drag Link 79-85 Toyota with 3" or more

Installation Videos


Pro Comp Promise

At Pro Comp, we know you have many choices when selecting products to personalize your vehicle. You should demand nothing but the highest quality available and have total confidence that the products you selected are the best in the industry. It is for these reasons that Pro Comp Suspension products are backed by the best warranty in the industry...the Pro Comp Promise!

Pro Comp promises that its products will last a lifetime or we will replace it free of charge. It's that simple! Because of our commitment to quality and manufacturing excellence, we are able to stand behind our products. FOREVER.

It is Pro Comp's Promise that if one of our suspension products breaks not due to misuse, neglect or vandalism, we will replace it. Whether you are the original purchaser or not, you can be assured that we will make it right. The Pro Comp Promise covers all suspension products including shocks and steering stabilizers. Buy Pro Comp Suspension today and enjoy it for the rest of your life!

That's our Pro Comp Promise!

Notice to Owner, Operator, Dealer and Installer:

Vehicles that have been enhanced for off-road performance often have unique handling characteristics due to the higher center of gravity and larger tires. This vehicle may handle, react and stop differently than many passenger cars or unmodified vehicles, both on and off–road. You must drive your vehicle safely! Extreme care should always be taken to prevent vehicle rollover or loss of control, which can result in serious injury or even death. Always avoid sudden sharp turns or abrupt maneuvers and allow more time and distance for braking! Pro Comp reminds you to fasten your seat belts at all times and reduce speed! We will gladly answer any questions concerning the design, function, maintenance and correct use of our products.

Please make sure that the Dealer / Installer explains and delivers all warning notices, warranty forms and instruction sheets included with Pro Comp product.

Warranty and Return Policy:

Pro Comp warranties its full line of products to be free from defects in workmanship and materials for the life of the product. Pro Comp’s obligation under this warranty is limited to repair or replacement, at Pro Comp’s option, of the defective product. Any and all costs of removal, installation, freight or incidental or consequential damages are expressly excluded from this warranty. Pro Comp is not responsible for damages and / or warranty of other vehicle parts related or non-related to the installation of Pro Comp product. A consumer who makes the decision to modify his vehicle with aftermarket components of any kind will assume all risk and responsibility for potential damages incurred as a result of their chosen modifications. Warranty coverage does not include consumer opinions regarding ride comfort, fitment and design. Warranty claims can be made directly with Pro Comp or at any factory authorized Pro Comp dealer.

IMPORTANT! To validate the warranty on this purchase please be sure to mail in the warranty card.

Claims not covered under warranty

  • Parts subject to normal wear; this includes bushings, bump stops, ball joints, tie rod ends and heim joints.
  • Finish after 90 days.
  • Damage caused as a result of not following recommendations or requirements called out in the installation manuals.

Pro Comp MX Series coil-over shocks are considered a serviceable shock with a one-year warranty against leakage only. Rebuild service and replacement parts will be available and sold separately by Pro Comp. Contact Pro Comp for specific service charges. Pro Comp accepts no responsibility for any altered product, improper installation, lack of or improper maintenance or improper use of our products.

PRO COMP Lift Shield Warranty

Pro Comp Lift Shield Warranty

Get Out There and Go For It...We've Got You Covered

For information on the Lift Shield, 5 Year / 60,000 mile Powertrain Warranty available on Pro Comp's most popular late model suspension systems visit the Lift Shield website.

Pro Comp USA passed the Federal Motor Vehicle Safety Standard (FMVSS 126) test 2014 JEEP WRANGLER JK 3.5


On March 23rd, at a proving ground in the Arizona desert, Pro Comp successfully tested and passed the FMVSS 126 Electronic Stability Control Test with its new 3.5” Suspension System on a 2014 Jeep Wrangler.

Adam Trowbridge, Brand Manager of Pro Comp Suspension, explains that the company elected to perform FMVSS 126 due to its relentless drive for quality. "The Jeep Wrangler is a vehicle continually pushed to its limits in the off-road environment. Consumers want a more impressive performing kit off-road, while still maintaining all of the vehicle’s safety features on-road. Pro Comp works hard to make sure our kits excel in both environments. We performed this physical test because we believe this stands as a symbol of our ongoing commitment to safety, engineering and technological advancement."

  • FMVSS 126 test final run, 300° right hand turn at 50 mph.

  • Data acquisition system and robotic steering wheel controller.

2014 Tundra 6 inch Pro Comp Suspension

Certified Compliant – FMVSS 126
Pro Comp Passes Electronic
Stability Control Test

Another industry first! Pro Comp is proud to announce that it has tested and successfully passed the Federal Motor Vehicle Safety Standard (FMVSS 126) test on a 2014 Toyota Tundra 4wd . This highly specialized test was performed to show that the installation of a Pro Comp 6-inch suspension system, Pro Comp wheels and 35-inch Pro Comp Tires would not compromise the performance and effectiveness of the vehicle's Electronic Stability Control system.

Pro Comp's testing was performed on a test track where the true capabilities of their products could be measured more accurately. This accomplishments is just another example of Pro Comp’s ongoing commitment to advancing the performance and technology of its products.

2014 Silverado 6 inch Pro Comp Suspension

Certified Compliant – FMVSS 126
Pro Comp Passes Electronic
Stability Control Test

Pro Comp is proud to announce that it has tested and successfully passed the Federal Motor Vehicle Safety Standard (FMVSS 126) test. This highly specialized test was performed to show that the installation of a Pro Comp 6” suspension system, Pro Comp wheels and 35” Pro Comp Tires on a 2014 GM 1500 4wd would not compromise the performance and effectiveness of the vehicle’s Electronic Stability Control system.

Unlike other manufacturers that have elected to do self-testing through laboratory simulation, Pro Comp’s testing was performed on a test track where the true capabilities of their products could be measured more accurately.

Testing was conducted on a 2014 Chevrolet Silverado 4WD. The truck was equipped with an off-the-shelf Pro Comp 6” suspension system, 20” Pro Comp alloy wheels and 35” Pro Comp Xtreme A/T Tires. The truck was then fitted with an elaborate array of sensors and test equipment to monitor all aspects of the vehicles movement and dynamics including a robotically operated steering wheel to assure precise and accurate tests.

On the closed test course, the Pro Comp equipped vehicle was accelerated to 50 mph at which point the test operator initiated the test and let the computer take over. The robotically controlled wheel spins abruptly; both left and right, up to 300 degrees in less than half a second and then returns back to dead center causing the truck to change direction and begin to slide. This event caused the trucks ESC system to activate and regain control. When the data was analyzed, it clearly showed that the Pro Comp products did not interfere with the performance of the ESC systems.

  • FMVSS 126 test final run, 300° right hand turn at 50 mph

  • Data acquisition system and robotic steering wheel controller

  • Brake pedal force gauge

  • Ultrasonic distance measuring sensor

Adam Trowbridge, Brand Manager of Pro Comp Suspension, explains that the company elected to perform FMVSS 126 due to its relentless drive for quality. “We performed this physical test because we believe this stands as a symbol of our ongoing commitment to safety, engineering and technological advancement.”

Certified Compliant – FMVSS 126
Pro Comp Passes Electronic
Stability Control Test with 6” Kit
on 2013 Ford F-150 4WD

Pro Comp is proud to announce that its 6” suspension system for a 2013 Ford F-150 has been tested and successfully passed the Federal Motor Vehicle Safety Standard (FMVSS 126) test. This highly specialized test was performed to show that the installation of a Pro Comp 6” suspension system, Pro Comp wheels and 35” Pro Comp Tires would not compromise the performance and effectiveness of the vehicle’s Electronic Stability Control system.

The truck was equipped with an off-the-shelf Pro Comp 6” suspension system, 20” Pro Comp alloy wheels and 35” Pro Comp Xtreme A/T Tires. The truck was then fitted with an elaborate array of sensors and test equipment to monitor all aspects of the vehicles movement and dynamics to assure precise and accurate tests.

Adam Trowbridge, Brand Manager of Pro Comp Suspension, is excited to offer their loyal customers another safe and quality product. “One of the key motivations of Pro Comp is to develop products that not only perform great, but ensure the highest level of safety to its users. We invest in these tests to give our customers peace of mind, knowing that our products have been put through its paces.”