V2Rocket

Hi,
I need to replace the bushings on my rear suspension soon. The spring plate bushings are entirely shot and the trailing arms can't be far behind.

My car is 30 years old this month so I think I got my money's worth for the stock ones

I am wondering if going with OEM-style rubber is worth the extra cost vs using the purple Powerflex bushings offered by Ideola.

My car is 100% street driven. Road quality here is crap, and I'm not willing to sacrifice ride comfort for the allegedly sharper handling that a poly bushing can provide due to stiffer compound. I don't want to have to grease anything which puts a potential negative on Poly.

I intend to upgrade torsion bars from stock 23.5 to 26mm while in there, but that spring rate change should be offset in the comfort category by new bushings/maybe new shocks.

So basically this is a question of ride comfort/noise vs cost. I know either option will be better than what I have now which is why I am considering poly. Experiences?

Dimi 944

I would recommend Delrin and you will not sacrifice any ride comfort.

SOB Racing

My experience with poly (non-Porsche) has been ride quality is fine, but your noise and vibration increases somewhat.

V2Rocket

From what I've read on delrin is that it is squeaky, harder, and wears out faster than rubber...is that your experience?

harveyf

If you check user experience with poly (as a generic term for any bushing made of hard plastic material, includes Delrin) versus rubber bushings, in general I think you would find a consensus that they will eventually sqeak. Anticipating this, folks go so far as to add grease fittings. They are harder, which is a good thing only from a pure going around corners at the limit standpoint. If you are driving on public roads to the point that this makes a difference to you, then you are a braver man than I am. Will they wear out faster? This is related to the squeak issue. Rubber bushings twist in the space between 2 metal rings, an inner ring and an outer ring. Poly bushings can't twist so one of the 2 surfaces has to slip. Thus there is squeak and wear that you don't get with a rubber bushing.

Another issue is the fitment. Read my post here http://newhillgarage.com/2013/06/13/...sion-bushings/ for the long version but fitting the poly bushing can be an issue.

A lot of engineering goes into OEM bushing design, at least of well engneered cars like Porsche. I am a big fan of OEM bushings if they are available, if you can afford them, and if you are driving on public roads vs the track.

As a counterpoint, our friend Sir Speedy put in the "black" bushings, which are best described as a softer version of the various poly compounds on his S2 and really likes them.

There is no real single answer to this question but that's my 2 cents worth.

Dimi 944

Not in my experience driving a dedicated track car. For the road, I cannot tell as I do not have them on my street car...yet.

bill3

Poly/delrin will definitely squeak and the ride will be worse (I have them on the front A arms). I second the "go with OEM" if you can afford it for any street driven car (my car is dual purpose street/track and I have Fabcar lower arms on the front for safety reasons)

V2Rocket

bumping this up as ordering will happen soon.

anyone trying to defend poly over rubber?

divil

I had the same decision to make recently, and I ended up buying Elephant Racing polybronze spring plate bushings, and spherical trailing arm bushings. Whatever about the spring plates, the trailing arm bushings are like the front control arm bushings in that they have to be able to move in more than 1 axis...only rubber or sphericals can do that properly. A solid bushing shaped like the oem rubber one seems wrong to me, form my understanding of how they work.

Unfortunately I haven't had a chance to install them yet so I can't actually offer any real feedback

MAGK944

I have Delrin spring plates on my daily driver, zero issues with squeaking. They were not a easy "drop-in" fit though, you need to clean up the metal where they contact on both the spring plate and the carrier then grease them up with thick poly grease before final fitting. I also have solid bearings in the rear trailing arms back there.

My theory is that Delrin works best when there is only one plane of movement so on the spring plates there is only up and down, especially if you positively locate the arms to stop any side to side forces at the spring plate. If you fit delrin on anything with two or more planes of motion, like the front a-arms I've found they squeak.

marc abrams

My experience with poly bushings is I had a 80 vette that the diff was leaking gear oil. So I pull the diff to reseal it. I noticed the front diff support was hammered, so I replaced all the diff support bushings with poly bushings. And while I was in there, I replace all of the rear suspension bushings with poly also. Well between the harsh ride and drive line noise transmitted to the frame a month later that car was back up on jack stands and replaced all that poly stuff with good ol' rubber. Didn't like doing that but, when I did the bushings in my Porsche, you can guess what I used. And thank the good lord for Elephant racing rubber spring plate kit, otherwise I would have been wrapping that spring plate with a bicycle inter tube.

MAGK944

Difference here is your trans poly bushes mounted the trans to the BODY, spring plate and rear trailing arm bushes do not connect to the body. There are huge rubber bushes and blocks that attach the whole rear end to the body, so if you replace the spring plate with Delrin or the rear trailing arm bushes with something more substantial, there is minimal to no noise transmitted to the body.

marc abrams

One thing I would like to add is I live in New York and the roads are rutty. My folks live in Florida. They got some nice smooth roads down there. So road quality may sway peoples opinion on what to use.