Carl Fausett

A direct replacement for part number 928 331 588 13 "Rear Control Arm Bushing" which is no longer available from Porsche.Item #40 in the schematic below.

The rear lower control arm is responsible for maintaining even tire wear and good alignment of the rear of the vehicle. If the bushings are worn, cracked, or flattened out, the rear alignment will be lost with subsequent tire wear and handling problems.

Our bushings are graphite-impregnated polyurethane, a step up from the original rubber. Polyurethane suspension bushings are popular wherever cornering performance is important because they hold their dimensions even under high cornering loads. For the 928 performance enthusiast, rear camber is lost mid-corner when the rubber bushings yield to their loads. Replacing them with polyurethane bushings means you will be able to maintain higher camber angles mid-corner and faster lap times!

Can be installed with the rear suspension in the car, but it is easier if you remove the link so you can get it to a press. Our instructions will show you how.

Our price includes all 4 bushings, 4 new replacement lower pin nuts, and instructions. The OEM bushings, when available, were a LOT more.

I would like to get some feedback on these and get some miles on them. I will let a few kits out at $95 (normally $129.50) so I can hear back from end-users what they think. I know what I think - I think they are fantastic, and I can hold a hard corner even better than before.

If you would like to read the installation instructions before purchasing, please follow this link and download them from the "Suspension" section.
http://www.928motorsports.com/install.php

Carl Fausett

I also have polyurethane replacements for the "banana link" bushings, number #22 in the picture above, but they are untested, so I do not have them available for sale as yet.

The one I am working on now is the polyurethane replacement for bushing #39.

I am focusing on those bushings that yield under lateral loads causing us to loose camber mid-corner. By going to the stiffer polyurethane, we will keep more of our rear camber mid-corner, and my hope is for lower lap times as a result.

FLYVMO

Are they out of stock AGAIN?

I just got 4 new ones a few months ago....someone must have bought the entire batch. Definitely appreciate the time and research you're putting into getting alternatives out on the market. Porsche seems determined to make it hard to acquire parts.

Cheers!
Carl

KenRudd

Any time frame on bushing #22 and bushing #39? If I'm going to tear the rear end apart, I'd rather buy them as a package and do all at once.

BC

For the rears, who other than someone like you, or myself, are ever even going to buy them? That's the issue.

FLYVMO

Small market, I agree...until more people realize their old rubber bushings are so hard and deformed that they can't get the rear aligned properly any longer or can't pinpoint that annoying vibration...

Sorry to hijack the thread Carl, nice work coming up with new stuff.

Cheers!
Carl

BC

True. I feel we are at a precipice with the car. You used to see dozens of crappy unrestorable ones on CL and elsewhere. Now you see less of those, more of the desirable and well taken car of ones, and the cost is increasing. How may of those will be driven in anger where someone actually notices these bushings are dried and cracked?

Carl - make these, but my word of caution is watch your distributor on those bushings. Urethane is a chemical reaction, technically. It is not completely stable over time, pressure, and heat. I bought some (a long time ago, and not from you) for the front lower a-arms. They were installed but never driven on.

They completely disintegrated in 5 years. Crumbled like erasers.

ROG100

For clarification and not to detract from the new product that Carl is offering - the parts are NOT NLA - Porsche up issued the part number to 928 331 588 15 and it is a currently available part. Current price $98 each so if these work good value for money.

Carl Fausett

I have the bushings and banana links done (#22) but they are untested.

I have the first poly bushing for #39 on my desk, don't like the fitment that much, going to another specification. I'd say about 2 months on this one. .

Carl Fausett

Certainly sounds like they were not cured correctly. Then they crumble like old erasers - you are right. May have been cheap imports? I have my bushings made in the USA and they are the same manufacturer I have been buying my poly bushings from for about 8 years. All 1st-rate quality, and never seen them harden or soften or change over the years. I have some of their products on my front and rear swaybars that are quite old and well-abused and they are still good.

Carl Fausett

Then that's the 2nd time I have seen them come back from the dead. I started these more than a year ago when they were not NLA but OOS, then a small batch of them showed up so I stopped. Then they went NLA (according to my contact at Porsche) and I re-started this project.

I would expect them to continue to be hit-or-miss from this point forward.

...And then there's the fact they are $98 each...

Lizard928

I honestly feel that poly eurathane should be outlawed in suspension conponents. Anyone who truly understands how it works would never use it.

Carl Fausett

That's a unique outlook.

So all the after-market suspension bushing kits are bad as well as our own well-tested polyurethane upper A-Arm bushings?

There are so many suspension bushings kits available from BMW's to Mustangs to whatever...

Please tell me why you have that opinion, and where is your data?

Lizard928

Carl,

You will not find poly bushings on ANY professional race car.

For the average autocross junky, or weekend track warrier you may. And just because they are made,and used by some, does not make them a good idea.

I have tried to explain how suspension bushings work to you in the past and will try to again. But before I do so, I will state for those less understanding, either stay with STOCK rubber bushings, or if you wish to track only your car go to full heim jointed/bearinged suspension.

The stock rubber bushings are a very dense injected rubber where there is a metal outer and inner sleeve that the rubber is bonded on to (90% of the parts). The rubber is adheared to the metal sleeves 100%.
For these bushings that are listed above, lets look closer at how the stock ones work.
The outer sleeve is pressed into a steel housing and cannot rotate.
The inner sleeve is held captive but the large pin that goes through them, the shock, and the hub. When properly tightened the inner sleeve it held 100% captive and rotates WITH the bolt/hub.
When you look and understand this, you then look for what does move.
Then you see that the rubber acts like a large rubber band, as the hub rotates the inner bushing rotates while the outer doesnt and the rubber twists. There is no rubbing of parts, there is no binding, or squeeking.

Then we look at poly/delrin bushings,
There is no bonded outer metal sleeve which is a press fit. The inner metal sleeve is not bonded either.
What this means is that there is no twisting, now there is a rotation, a rubbing as it were.
The inner sleeve is still captured by the hub/pin so that the rubbing doesnt occur on the pin itself.

However where you have rubbing, you have wear.
This is why poly sway bar bushings make noise. As will these bushings.
Where things are rubbing they will wear out. Where they are driven on the street there will be dirt that gets in between the parts and they will wear out in as low as 1k miles.

Poly/delrin does have some uses though, for example, the delrin bushes that Roger sells to hold the rack are an excellent use. Or where they make poly pieces for reinforcing motor mounts on a great deal of tuner cars.

If you use these do NOT drive with them on the street. If you use them on the track, inspect for wear/play every time you come into the pits, and keep spares on hand.

ROG100

928 331 588 15 = 288 sitting in Germany with about 30 in the USA so not likely to go out of stock anytime soon. As I said yours are certainly better value.