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The following points are provided to help you understand the application of Urethane bushings and points to
keep in mind to fit them properly to your car.
Major Premise: All suspension pivot points that use rubber bushings have a wide dimensional tolerance range,
of which the rubber bushings easily compensate for.
Minor Premise: Because of the above fact, making a "one size fits all" bushing is dimensionally impossible, so
individual fitting is mandatory.
1) Hardness of the Urethane: The durometer reading (a scale used to measure the relative hardness of
softer items) of our bushings is in between what used to be called a "race" bushing and a so-called
"street" bushing. In other words, they are hard enough to largely maintain suspension alignment settings
but soft and compliant enough to isolate noise and not degrade ride characteristics.
2) Lubrication: The Urethane has graphite mixed into the batch prior to pouring, so to a certain degree,
the bushings are self-lubricating. We've had very good luck using any good moly grease such as
Swepco®, etc.
3) Location: After fitting, mark or number each bushing and write it down on a piece of paper so you know
where it is supposed to go.
4) Fitting: Each bushing needs to be individually fitted; there is just no way around this. Maybe you'll get
lucky and they will fit the OD of the housing and then also fit the control arm, but the chances are
statistically poor. Changing the OD can be done using a lathe or a belt sander or even a coarse file. The
ID can be enlarged with a lathe or a drum sander (the larger the OD of the sanding drum, the better).
5) Fit Definition: The fit is correct when the suspension parts can be moved with very little effort when
moved by hand - let's say less than 5 ft-lbs of torque. It's almost better to have the fit be just a bit loose
than it is too tight.
6) Fitting Sequence: Press the bushing into whatever housing it will be in, ie, torsion housing, spring plate
cap or front arm housings. If it fits just snugly, leave it, if you have to jam it in with a hammer or press,
adjust the shape or dimensions until it fits just snugly - this is important because if you don't fit the OD
first, the ID will change when installed. Then fit the ID until the fit is correct. In the rear or spring plate
area (without the torsion bar installed), you want to be able to grab the spring plate and move it up and
down without herniating yourself - it should be snug, but not hard to move. The fronts should be pressed
into the front and rear housings and then the ID adjusted. When the arms are reinstalled on the car, the
arms should swing up and down with little effort of one hand. Shims may be needed to get proper
alignment of the A-arms; they can be added to the front mount of the A-arm. Be sure to liberally
lubricate the bushing prior to final assembly.
FYI: If you've ever installed a set of bushings that did not fit correctly and were forced in place and then tried to
corner weight the car and could not get the car to duplicate its readings, poor bushing fitting is often the reason.