silver & red CE

I'm ready to order poly bushing for my rear suspension, which points should I use poly?

Differential carrier bushings
Strut rods (spindle rods?) bushings
Upper and lower shock bushings
Leaf spring bushings
Upper and lower control arm bushings

I'm ready to do all points except the control arm bushings. I've heard that there needs to be some compliance in the suspension and if I use poly in the control arms, the suspension can bind. Any truth to this idea?

Eric


[Modified by silver & red CE, 2:59 PM 12/19/2001]

SPD DMN

All of my rear end is poly. I have had no binding problems whatsoever.

vader86

use them everywhere.

JasonL

By upper/lower "control arms" I assume you mean the trailing arms. I know trailing arms are called LCAs on F-bodys and other live axle cars, but I personally think the spindle rod is more accurately called the control arm on a C4...

Anyways, I have heard from some racers (fast BSP drivers) that the rear will bind with poly on the trailing arms. So I plan to leave that part alone. Judging by my glances at the rear suspension, I could definately see this as being a potential problem. Maybe hrocks will comment more...

RED90SIXLT1

Use them everywhere EXCEPT the diff carrier. Use the stock rubber bushing here...if you don't you'll regret it. Read the posts here and every time someone does something to their it is always THE GREATEST thing they did. Well the truth is...most wont admit when it isnt just right. When you replace the carrier bushings with poly every bit of vibration goes through the chassis of the car and up your spine. Trust me...use the rubber bushings there.

danno85

I bought a rear set from PST and it came with poly bushing for everything, including the big ones in the differential cover.

As far as binding, I think that depends alot on how tight you clamp the stamped steel bracket down on the sides of the bushing when you tighten the bolts. That can definitely put it in a bind.

danno85

That's good input! I think I'll try mine without replacing the carrier bushings first. Thanks!

JasonL

Actually, the inherent design of the trailing arm and its bushings is somewhat flawed (on C4s and many other cars). The trailing arm is there to restrict fore/aft movement of the knuckle...fine. It should also allow the knuckle to freely move up/down through the suspension travel...fine, the mounting bolts just rotate inside the bushings. The problem arises when you have an IRS and the wheel swings an arc toward the center of the car as the rear of the car compresses. This puts a "twist" on the bushing, and the poly doesn't want to give. A heim-joint here would solve much of this problem though, I think.

I think the question is whether the binding occurs to a significant degree or not. Poly DOES flex, just a lot less than rubber.


[Modified by JasonL, 5:20 PM 12/19/2001]

silver & red CE

The FSM calls them "upper and lower control rods" and "spindle rods" (page 3D7). Rippie calls them "control arms" and "strut rods". Needless to say, this is adding to my confusion.

Eric

Bill Reid

... respectfully I disagree. I have a 100% poly bushing suspension. I have no problems with binding. I do have Z51 suspension... and for an 85 it is my opinion that the stiff springs are what transfers vibrations to the body and interior. Can't comment on other years other than from what I hear poly only makes it better due to progressive softening of the springs over the years up to 96. While poly may assist in the transfer I don't think its so much that I would shy away from changing the diff carrier bushings. I would suggest changing a few links to poly at a time to see how it changes your handling. You may or may not like it. Diff carrier bushings are tough to get out... and the poly takes a press to get them in. All other bushings in the rear are very simple to change.