Only desire replies from members who have replaced their rear subframe (engine cradle) bushings, that is, members with experience not just opinions.

What did you replace them with: rubber, poly or aluminum?

What changes did that make to your handling?

How did it affect the straight line ride quality concerning bumps, potholes and or expansion joints.

I added poly cradle bushings.
was my first "suspension" mod - if you could call it that.
if slightly reduces the "floaty" feel of the back end
and that floaty feel will never fully go away - unless you go super stiff in the rear end.

if you are having troubles with bumps, potholes & expansion joints - I would say you have bad struts.
if they are original struts - then - yes - I know you have bad struts. because even the original struts SUCK compared to todays struts.
well - except for the expansion joints. now - if they are uneven joints - then - yes - still struts - but if they are even - you may want look into new tires.

yes - the first 3 things just about EVERY Fiero needs: Cradle bushings, Rear A-Arm bushings & Struts
tighten up that sloppy rear end.

I added poly bushings.

As Pyrthian states it reduces the "floaty" feel. Hitting bumps and such in a straight line really didn't change much aside from the float. Cornering felt firmer. Another thing that I noticed was less torque steer on accel/decel. Just to give a reference, My cradle bushings were original with 86K miles on them so they were a little worn/soft and the poly was a huge improvement. I would assume that new rubber bushings would also have been an improvement but I cannot say what differece there would be between new rubber vs. poly.

------------------

Happiness isn't around the corner...
Happiness IS the corner.
ZZ4 Powered !!

My 86 Coupe has that floaty feeling over 50 MPH , I hate that

I went to aluminum for my '84, and am doing the bumpsteer mod.

quote Isolde:I went to aluminum for my '84, and am doing the bumpsteer mod.

Have you driven it on the road since the conversion?

I replaced mine with poly. Along with the rear control arm bushings and I'm very pleased with the results. I can't say new rubber wouldn't be any better because the existing rubber was all original and in sad shape. Definitly tightened the ride up but I also basically rebuilt the entire suspension, front and rear. '87 GT 2.8

I have poly cradle busihings on both my 87 GT's, poly control arm bushings and rear sway bars. I do notice a slightly firmer ride but the handling is much improved. I am not sure if this is the result of just the bushings, the sway bar or the KYB struts or a combination thereof.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

i went with poly first and then installed the aluminum bushings .i noticed not much difference with poly .the al mounts tightened things up quite a bit though .i guess it really depends how bad your rubber is and i guess mine had not deteriorated that much .for my money , go straight to aluminum .there really is no need for cradle isolation .the 88's are solid mounted so that should tell you something .

I am going to agree with wftb about the 88s being solid mounted.

Thats why I went Al on the cradle and poly everything else front and back. It made a really big difference in the floaty feeling others have mentioned, and i dont really seem to have almost any torque steer. As far as cornering is concerned, I thought my worn out 84 was the cats meow, not anymore the poly Al combo is the way to go. Personally though I think the bumpsteer actually got a little worse, but that might just be the camber and alignment. Also the suspension, springs and struts are old so that probably contributes.

Hello

Odd as I am…..I did the opposite. On my 88, I modified the rear geometry to use equal length instead of stock unequal length lateral links. All control points are solid spherical rod ends. The result was zero toe and zero bump steer. The handling was VERY solid a VERY accurate but the chassis noise was VERY uncomfortable. Than I rubber mounted the entire rear cradle. The car now feels just as good but now the road noise stays out side. I believe that because the geometry is so correct, the “soft” cradle mount has almost no effect on handling.

Yellow

I went to poly bushings everywhere on my '86 GT, so like most other people, it's hard to say how much the cradle bushings contribute to the tighter feel.

Now for the opinion: it's doubtful the cradle bushings have much impact, if any at all, on the handling of the car. For them to have an impact, they would have to allow the entire cradle to shift fore and aft, side to side, and/or up and down appreciably. Say for a moment that this was the case, then, since all of the rear suspension moves in relation to the cradle as a single unit except the strut tops, there would have to be a significant amount of movement of the cradle to effect even a very small angular change in the strut given it's long length. This is unlikely to happen given the design of the cradle mounts fore and aft.

Again, in my opinion, Yellow-88 hit the mark with his observation about noise. The cradle bushings main (if not sole) purpose is to isolate NVH (noise/vibration/harshness) levels inside the cabin.

Does poly or aluminum produce an increase in cabin noise?

The harder the material used for bushings, the more the noise (ie vibrations) will be transferred from one component to another since the energy won't get absorbed by the bushing. Rubber theoretically should produce the quietest environment, but the largest movement, while aluminum will transfer the most noise but prevent any relative movement bewteen the parts. Polyurethane is a compromise between the two.

yellow 88 , i would like to to see pics of your set up .as far as an increase in cabin noise with solid mounts , i did not notice any increase in noise .since i still have poly in the suspension components , there is lots of noise isolation .my car is very quiet .

quote Originally posted by Bloozberry: The harder the material used for bushings, the more the noise (ie vibrations) will be transferred from one component to another since the energy won't get absorbed by the bushing. Rubber theoretically should produce the quietest environment, but the largest movement, while aluminum will transfer the most noise but prevent any relative movement bewteen the parts. Polyurethane is a compromise between the two.

while this is true - the cradle does not produce noise or vibrations.
the engine & the suspension do - and they are rubber or poly mounted. there is no more noise/vibration than any other car by mounting the cradle solid.

i have an 84 w/350sbc i replace COMPLETE SUSPENSION last here except for cradle
bushings went eith rubber everywhere and koni. As you can imagine it made a huge
difference, but my cradle was rusted so it had to go this year. I used aluminum bushings
and swapped my contol arms to poly. Now i just got it on the road 3 days ago and noticed
a huge difference, my alignment was way out of wack and i notice i FEEL the suspension
vibration or maybe movement is a better word. It's not a bad thing i believe it enhances the driving
experience more. Ray

All my Fieros have aluminum cradle bushings. The most obvious change is there is more understeer than before. The cause is most likely the fact that the car feels more stable in the turns and I have a tendency to push it to the limit. There is no noise from the cradle...I don't know how there could be with no movement. IMO, the best suspension upgrade I did.
Dave

------------------

1987 GT (my toy-see above), 1987 GT 3800s/c, 1986 SE with a VW VR6, certified master technician/shop owner
www.njautobahn.com
www.hausofguru.com

quote Originally posted by Pyrthian: while this is true - the cradle does not produce noise or vibrations. the engine & the suspension do - and they are rubber or poly mounted. there is no more noise/vibration than any other car by mounting the cradle solid.

While technically correct, Pyrthian, the cradle does have a resonant frequency at which it will vibrate naturally and if the source of that excitation is allowed to go undamped, the part will vibrate uncontrollably to failure. I'm not saying that would happen with the cradle, but clearly the folks at GM were concerned enough that either engine (but more likely road) vibrations could get the cradle to transfer low frequency noise to the rest of the frame, otherwise they wouldn't have spent the extra money for bushings. By 1988, they decided the NVH factor wasn't worth the extra money for the bushings and hard mounted the cradle, or the changes to the cradle were enough to change the resonant frequency to a level they thought was acceptable.

ALL metal has a frequency it will resonate at. every bracket, every peiece of the space frame, etc. GM rubber mounted because that is standard practice - rubber mount body to frame. I would expect the rubber pucks on the rear are the same rubber pucks used to mount Chevy trucks to their frames.

quote Originally posted by wftb: i went with poly first and then installed the aluminum bushings .i noticed not much difference with poly .the al mounts tightened things up quite a bit though .i guess it really depends how bad your rubber is and i guess mine had not deteriorated that much .for my money , go straight to aluminum .there really is no need for cradle isolation .the 88's are solid mounted so that should tell you something .

Keep in mind that they also improved the ride in '88, so that contributed to the decision to go with solid mounts as opposed to creating the "buffer" that the rubber early cradle mounts provided. But definitely, for handling, solid is better!

quote Originally posted by wftb: yellow 88 , i would like to to see pics of your set up .as far as an increase in cabin noise with solid mounts , i did not notice any increase in noise .since i still have poly in the suspension components , there is lots of noise isolation .my car is very quiet .

Yellow just happens to be on jack stands getting a cleaning and inspection so I can do pictures this weekend. Hopefully you can wait.

Poly is a complient material so it will isolate most road noise. Yellow has SOLID rod ends at all control points so they transmitt ALL "noise" from anything solid that touches the hub carriers. That is the engine, the gearbox and the wheels. I have solid bushing up front also and that cradle is also rubber mounted.

With this setup there is just about ZERO tolerance in alignment. If it is off, it feels REALLY bad but when it's on it feels REALLY good. I mean R E A L L Y good.

Yellow

Mine was spooky above 70 mph, and the '88s were solid mounted, so I did aluminum. No regrets. Ride quality is actually a little better, now that the suspension can do it's job. I was able to keep up with a Corvette running down into Flaming Gorge, where HP didn't matter. I did end up with some brake fade, but that's off-topic.

quote Originally posted by Isolde: Mine was spooky above 70 mph, and the '88s were solid mounted, so I did aluminum. No regrets. Ride quality is actually a little better, now that the suspension can do it's job. I was able to keep up with a Corvette running down into Flaming Gorge, where HP didn't matter. I did end up with some brake fade, but that's off-topic.

Unless the're made of Jello.....cradle mounts have nothing to do with the suspensions "ability to do it's job".

Yellow

worn out, decomposed, rotten rubber is not far different from jello. The difference was night and day.

quote Originally posted by Isolde: worn out, decomposed, rotten rubber is not far different from jello. The difference was night and day.

Oh....I agree. If the front and rear wheels are not on the same page....the confusion would be pretty spoocky for the human in between.

On pre 88 cars, I go with baisc poly everywere. Install a anti-roll bar and. Install new tie rods and wheel bearing if there is ANY slop AT ALL. Finaly..... set toe to zero and enjoy.
Nice stiff tire/wheels ...but thats another thread...

Yellow