Comp Lift Kits have always favored an approach centered on forward
progression and self-improvement, and the results can be seen
in the past success of Pro Comp Suspension Lift Kits. Sticking
to the philosophy of constantly upgrading technological standards
and managing value and ease of use for customer benefit, Pro
Comp Suspension aims to maintain the extraordinary march to
brilliance that has made Pro Comp Suspension Lift Kits industry
frontrunners for many years.
Pro Comp is globally recognized as one of the leaders in off-road
technology. Since 1992 we’ve been manufacturing high quality,
durable products for on and off road racers and enthusiasts.
Pro Comp has created value for its customers by improving product
performance and integrating new technologies. Our commitment
to maintaining the utmost in quality and durability is what
drives us and continues to be our mission statement. From concept
to reality the results are obvious. Pro Comp builds suspension
systems that work!
Explorer ProComp Performance Systems turn mild-mannered, vanilla-looking,
stock-equipped trucks and sport utilities into the hottest machines
on the road. Paved or dirt. Fact is, ProComp gear gives you the Competitive
Edge in almost any category you'd care to explore! The reason: we
build our own stuff. We design it, engineer it, fabricate it, assemble
it, even powdercoat it in our ProComp Factory. That's what we mean
by Competitve Edge Performance.
we review Pro Comp suspension system components and how they
work together, remember that a vehicle in motion is more than
wheels turning. As the tire revolves, the Procomp lift kit is
in a dynamic state of balance, continuously compensating and
adjusting for changing driving conditions. Today's Pro Comp
lift kit is automotive engineering at its best.
The components of the Procomp lift perform six basic functions:
correct vehicle ride height
effect of shock forces
correct wheel alignment
tires in contact with the road
vehicle's direction of travel
However, in order
for this to happen, all the Pro Comp lift components, both front and
rear, must be in good working condition.
COMPONENTS OF A MODERN PRO COMP LIFT KIT
this point, it's important to understand that the main components
of a moving Procomp 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
The Pro Comp
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.
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 Procomp 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.
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.
discussing Pro Comp 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.
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
most commonly used spring in Pro Comp lift kits 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.
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.
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
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.
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
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
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.
type of Procomp 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
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
Comp Strut mounts are vehicle specific, and there are numerous
designs in use today on both front and rear Procomp 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.
important component of a Pro Comp suspension lift kit 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.
ushings 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
Pro Comp 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.
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.
stated, Pro comp 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.
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.
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.
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.