2005 on Chrysler LX Chassis: Chrysler 300C, Dodge Charger, Challenger
and Magnum
The LX series chassis is a product of Daimler Chrysler shared
engineering. The chassis delivers excellent ride comfort and control and
has been a tremendous success with approximately 900,000 units in the
field. As good as these vehicles are owners and fleet mangers report
relatively short tire life in what they consider to be conservative use.
Tire wear is directly related to two characteristics in the LX chassis.
One is a high rate of bump steer. A contributing factor to premature
tire wear from bump steer are worn, torn or failed radius rod bushes.
Two is high negative rear camber when the vehicle is carrying a load.
What is bump steer?
Bump steer is the toe-in or toe-out of the front wheels as the
suspension goes from normal ride height through full bump (suspension
system moves up) to full droop (suspension system moves down).
Measurement is usually limited to 3" up and 3" down from ride height. It
is specified either by a graph or measurements.
Why does bump steer cause tire wear?
The toe in and toe out motion created as the suspension articulates over
the road surface literally scrubs the tread off your tires. You can
create the same grinding motion with your feet. With your feet flat on
the ground, grind them until your toes point out and point in. The
resistance is what causes tire wear as bump steer occurs.
How is bump steer corrected on a Chrysler LX chassis?
Bump steer is corrected by raising or lowering the steering rack in
relation to the wheel knuckle at rest. At Pedders we use an EP2113 Bump
Steer Correction Kit to raise the steering rack. Installation of the kit
take approximately one hour and should be performed with your next wheel
alignment or when you purchase tires. The graph demonstrates the
improvement.
How do I know if my radius rod bushes are worn, torn or failed?
A Radius rod bush can be inspected with the vehicle on a lift and a
flash or shop light. As rubber ages, ozone causes the surface of the
rubber to oxidize. A reddish brown ring where the radius rod bush moves
is completely normal and requires no maintenance. A radius rod bush
with cracks, tears or worse should be immediately replaced.
Not only does the excess motion of the radius rod arm caused by a bad
bush contribute to tire wear, it creates steering that is sloppy and
contributes to wandering and pulling under way or when stopping.
YouTube - Chrysler LX Radius Rod Bushes and Why they Fail
Chrysler offers replacement only of the entire arm and bush assembly.
Pedders EP6567 is a severe duty cycle bit that replaces only the bush
making it very cost effective. The manager or technician will walk you
into the shop so you can see the condition of the bush.
What is Camber?
Camber is measured in degrees, both positive and negative. Camber can be
the result of a bad alignment, wearing parts and changing the ride
height on your vehicle; rather raising or lowering it. Camber takes
valuable rubber off the road by ridding on the edges of the tires
instead of the traction patch. Positive camber points the top of the
wheel away from the vehicle. Negative camber points the top of the wheel
in towards the vehicle.
Why does the LX chassis have high negative camber under load?
If your LX is equipped with Nivomat load carrying rear shock absorbers
from the factory, your LX will not have high negative camber when loaded
with passengers or cargo. The Nivomat is a self-contained hydraulic load
leveling system. As long as the Nivomats are working they will level the
vehicle and keep the negative camber in check. The technician can
determine if your LX has Nivomat rear dampers by measuring the OD of the
lower shock tube. If it is over 59mm in diameter your LX is Nivomat
equipped. Most of the LXs were delivered from the factory with standard
style rear dampers. The coil rate, the ability to carry load is
conservative. Typically the negative rear camber will increase 1.5 to
2.5 degrees with five passengers in the vehicle.
How do I correct the negative camber with passengers or cargo on my LX?
Coils are like people, they age with time and use. You could replace
your worn OE coils with new OE coils. They will be better, but still
light in rate by enthusiast and Pedders standards. Even brand new OE
coils will measure 1 to 2 degrees of negative camber with the same load.
Replacing the rear coils with Pedders 7841 HD coils. With Pedders 7841
coils installed the change in negative camber with identical load is .5
degrees. Your vehicle will ride a bit firmer, but most LX owners
actually find the ride to be very close to factory.
What is the warranty for Pedders parts used on my LX?
The warranty is straight forward and covers both parts and labor. If the
Pedders parts are installed by a Pedders Dealer and bit fails in 2 years
or 36,000 miles they parts will be replaced at no charge. If they are
installed by a DIY or other shop the parts are covered but labor is not
covered.
If you drive an AWD LX you should be aware that lower front control arm
bush failure is more common than radius rod bush failure. The AWD lower
front control arm combines the function of the radius rod arm and the
control arm into a single unit. The arm is robust. The inner bush is
prone to wear. This arm is from a 300C with a 3.5 and has been driven
conservatively by a mature owner for 53,000 miles.
The only available solution is replacement with a Chrysler OEM control
arm assembly. Pedders has a replacement bush in development.
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