Poly vs. Cradle Mounts

CincinnatiFiero · Post by **CincinnatiFiero** » Sat Apr 19, 2008 6:20 pm

Since the cradle is out on the 87 and I had to destroy the mounts to get it out, I may as well upgrade my mounts. So here is the question, poly or aluminum?

Poly is $55, aluminum is $85, theres one pro off the bat. I like the idea that poly will still have some give, but the solid cradle in my 88 doesn't bother met. Lets hear your opinions.

Xanth · Post by **Xanth** » Sat Apr 19, 2008 6:27 pm

I vote aluminum, don't get why they decided you need a floating cradle. Not to mention the suspension is mounted to the cradle, just seems like an unnecessary amount of movement.

Aaron · Post by **Aaron** » Sat Apr 19, 2008 7:14 pm

CincinnatiFiero wrote:I like the idea that poly will still have some give

There's no reason for your cradle to have play. That is what we have suspensions, and poly/rubber motor mounts for.

Aluminum.

The Dark Side of Will · Sat Apr 19, 2008 8:18 pm

The Fiero cradle is rubber mounted because the Citation cradle is rubber mounted. Who the fuck knows why the Citation cradle is rubber mounted... It's a stupid idea in that car also.

If you want the car to handle predictably, you need to keep the suspension geometry consistent. That's partially done by making the cradle as rigid as you can.

CincinnatiFiero · Post by **CincinnatiFiero** » Sat Apr 19, 2008 9:14 pm

Other fiero buddies are saying aluminum too, the only people I know with poly have them beause they bought the whole prothane kit.

Kohburn · Post by **Kohburn** » Mon Apr 21, 2008 8:25 am

the poly mounts are really stiff and drop in easy. I used them because they were half the cost of aluminum, go in easier, eliminate movement just as well. if they do anything that aluminum doesn't then it would just be reducing some of the high frequency vibration.

imo i'd just use poly unless your exhaust is going to be close to the mounts and you are pushing a lot of power. if the exhaust gets too hot near them it can cause them to melt.

Series8217 · Post by **Series8217** » Mon Apr 21, 2008 3:09 pm

Poly moves more than you think.

Kohburn · Post by **Kohburn** » Tue Apr 22, 2008 9:25 am

Series8217 wrote:Poly moves more than you think.

and how much does it move compared to how much you think that I think it moves? have you tested its movement on the craddle? because if not then you can't make that statement.

yes it provides a certain amount of cusion on a-arm bushings and sway bar end links. but the forces are a lot different on the craddle and the bushings are also a lot different on the rear of the craddle. the poly is also about as stiff as bass wood. you will likely get more movement out of frame flex than the bushings on the rear end of the fiero.

so IMO the only reason to go aluminum is for heat concerns.

Pyrthian · Post by **Pyrthian** » Tue Apr 22, 2008 11:08 am

Kohburn wrote:
Series8217 wrote:Poly moves more than you think.
and how much does it move compared to how much you think that I think it moves?......

why am I picturing a scene from the movie Dodgeball? :scratch:

whipped · Post by **whipped** » Tue Apr 22, 2008 12:41 pm

I honestly don't think you're ever going to be able to feel the difference.

It's like an extra 15 hp. Bragging rights? Maybe. But swap them back and you'd never know. Unless you're a Nurburgring veteran or something trying to shave off 0.1 sec

Just don't get rubber and you'll be fine.

Series8217 · Post by **Series8217** » Tue Apr 22, 2008 3:29 pm

Kohburn wrote:
Series8217 wrote:Poly moves more than you think.
and how much does it move compared to how much you think that I think it moves? have you tested its movement on the craddle? because if not then you can't make that statement.

I have not tested its movement on the cradle. I used it on 88 lateral links and it compressed over 1/4" from cornering forces. It's the same material as used on the cradle bushings.

yes it provides a certain amount of cusion on a-arm bushings and sway bar end links. but the forces are a lot different on the craddle and the bushings are also a lot different on the rear of the craddle. the poly is also about as stiff as bass wood.

Polyurethane deflects wayyy more than bass wood. I can easily deform the polyurethane bushings with my fingers. It's not very hard!

whipped wrote: It's like an extra 15 hp. Bragging rights? Maybe. But swap them back and you'd never know.

Unless you started with 100 to 130 hp...

Kohburn · Post by **Kohburn** » Wed Apr 23, 2008 7:27 am

Series8217 wrote:Polyurethane deflects wayyy more than bass wood. I can easily deform the polyurethane bushings with my fingers. It's not very hard!

then you got shitty poly. stuff i had was hard. not soft poly like they use in the universal trans mounts

Pyrthian · Post by **Pyrthian** » Wed Apr 23, 2008 9:52 am

Series8217 wrote:
Kohburn wrote:
Series8217 wrote:Poly moves more than you think.
and how much does it move compared to how much you think that I think it moves? have you tested its movement on the craddle? because if not then you can't make that statement.
I have not tested its movement on the cradle. I used it on 88 lateral links and it compressed over 1/4" from cornering forces. It's the same material as used on the cradle bushings.

yes it provides a certain amount of cusion on a-arm bushings and sway bar end links. but the forces are a lot different on the craddle and the bushings are also a lot different on the rear of the craddle. the poly is also about as stiff as bass wood.
Polyurethane deflects wayyy more than bass wood. I can easily deform the polyurethane bushings with my fingers. It's not very hard!

whipped wrote: It's like an extra 15 hp. Bragging rights? Maybe. But swap them back and you'd never know.
Unless you started with 100 to 130 hp...

well - with the lateral arm - you are also adding leverage of the lateral arm. with cradle bushings - they bushings are on the outside, and the leverage is the other way around. and, more mounting points.

kinda like a wrench on a poly nut vs a wrench held in a poly holder. yes - you can move the wrench on a poly nut. but - you aint moving the wrench in the poly holder.

and - yes - as mentioned - if you can deform the poly by hand - somethign went very wrong.

CincinnatiFiero · Post by **CincinnatiFiero** » Wed Apr 23, 2008 2:36 pm

I ordered aluminums last night from a friend, thanks for the input guys.

crzyone · Post by **crzyone** » Wed Apr 23, 2008 6:40 pm

Aluminum FTW.

MstangsBware · Post by **MstangsBware** » Wed Apr 23, 2008 9:23 pm

To late I guess but I vote for an 88 cradle swap.

CincinnatiFiero · Post by **CincinnatiFiero** » Thu Apr 24, 2008 2:35 pm

I vote for that too, but its not in the cards right now, I don't have the moola or the donor car.

nfswift · Post by **nfswift** » Tue Apr 29, 2008 7:47 pm

Poly is great for convenience... where can you get a "full AL bushing kit"?
I'd be interested to check one out, seeing as the cradle is coming out and a 3500 is going in, alum mounts would be pretty nice.

What's the big deal about 88 cradles? Isn't a pre 88 with an aftermarket swaybar just as good? Drop me some knowledge?

Boscolingus · Post by **Boscolingus** » Tue Apr 29, 2008 8:23 pm

Full AL cradle bushing kit available at WCF...

The big to-do about the 88 cradle would be the overall suspension design, as it is greatly worshiped over that of the pre-88.

To me it just seems like too much brain damage to mod and the geometry is never trully "right" after all the butchering to the shock towers that I have seen, however with all the rocket surgeons over on P F F chances are that I simply just havent seen the swap performed correctly.

To me a pre-88 cradle loaded up with Delrin/AL bushings on the pivot points far out weighs the butchering needed for an 88 cradle install.

Also, kinda touching base on the roller bearings for suspension thread, how come nobody has stepped up and tried using the spherical rod ends that you see some of the off road trucks/buggies using - I don't mean simple hiem joints, but rather pre-assembled units

hang on, let me grab a link......

http://www.ballisticfabrication.com/263 ... -1226.html

Now I have seen these that I could swear would almost be the perfect size to press into the a-arms, thereby bitch-slapping rubber AND poly suspension bushings at the same time

....discuss....

The Dark Side of Will · Tue Apr 29, 2008 8:50 pm

Boscolingus wrote:To me a pre-88 cradle loaded up with Delrin/AL bushings on the pivot points far out weighs the butchering needed for an 88 cradle install.

The early rear suspension isn't even close to the '88 rear.
My Northstar car is about as built as built gets with stock geometry. It's an '87 GT with aluminum cradle bushings, UHMW control arm bushings, Koni coil overs, 325x12 springs, rear bar with rod end links, 16x8 wheels and 255/50-16 Firehawk SZ50-EP tires. The front was just as built with solid bushings, rod end links, Koni shocks & stock springs. It had 16x6 wheels with 215/55-16 tires.

While that car's laid up, the current ride is a Formula that's stock except for Konis all around and rod end lateral links in the rear. It has stock wheels and cheap tires in stock sizes.

The Formula has a more controllable lift-throttle reaction than the GT and is MUCH easier to recover once the tail is out. You can DRIVE the Formula through a slide... in the GT you've just got to stay on the gas and pray. It does GREAT on hillclimbs, but it's scary going downhill.

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