Originally Posted by Kevin in Atlanta (Post 17405270)

1. Is this lower control a candidate for new bushings? The PS side spins and polished the aluminum.
2. Who sells the bushings?
3. Extra credit question: How does this happen on a 100k 89 S4?
4. Can bushings be replaced while the lower control arm is on the car?

Originally Posted by Kevin in Atlanta (Post 17405270)

https://cimg8.ibsrv.net/gimg/rennlis...945d4ccb24.jpg

1. Is this lower control a candidate for new bushings? The PS side spins and polished the aluminum. Yes, virtually mandatory if you are trying to get the car back to anywhere near the original handling. The "wear" on the aluminum arm will be minimal. That "radiused" area (which looks like it got sanded from dirt) actually looks that way, originally. They wanted that surface to be as rough as possible to help keep the rubber from rotating.
2. Who sells the bushings? 928 International. I believe Mark has both the bushings separate or the rebuilt lower arm.
3. Extra credit question: How does this happen on a 100k 89 S4? Super common. Expecting a rubber suspension bushing to last over 30 years is the mistake that people make.
4. Can bushings be replaced while the lower control arm is on the car? With the proper tooling, almost anything can be done. However, why would you want to? That lower arm is about 5 minutes from being in your hands.

Edit: Additional research reveals that the front bolts must be torqued to 88 ftlbs and while on the ground. I suspect a previous mechanic did not do that.
Only the rear matters when tightening. The front is designed to twist, from the initial position.

Originally Posted by FredR (Post 17405356)

The arm is buggered as is. No, what is pictured there is 100% normal. Whether it can be refurbished by Mark at 928 International remains to be seen depending on how much metal has been lost in the polishing process that should never have happened.
As I understand the stock bushings are not directly available and the arms are remanufactured in Germany- presumably by some outfit who made them originally?
Age related deterioration probably takes out the rubber - I often wonder if ozone may play a role in this process given the proximity to the alternator- stranger things have happened.
I suppose if one tried hard enough and had the right kit, the bushings could be replaced with the Powerflex type of bush with the arm still attached to the lower ball joint but why would you want to do such when it is so easy to remove the lower arm?. The lower front arm has a large amount of spring rate, because the rubber twists, instead of rotating. And since the rubber isn't supposed to rotate, but deflect only, that spring rate is progressive...the farther the arm travels, the higher that spring rate goes. Replacing the lower arm bushings with Powerflex bushings, without taking into consideration the change in spring rate turns out to be very interesting, if no other changes are made....whoever does this needs to be well experienced with oversteer.

Originally Posted by GregBBRD (Post 17405586)

Originally Posted by FredR (Post 17405733)

What you appear to be saying is that if Kevin pushes the spigot back into that bush it will be OK to use once more. My point of view is that that arm is shot until such time as it gets refurbished and even then the folks doing the work may conceivably reject it as being suitable for refurbishment albeit I suspect that would not be the case
I'm absolutely not saying that he can re-use the lower arm without new bushings! I'm not even sure how you could possibly come to that conclusion.
When you say:
The arm is buggered as is. Whether it can be refurbished by Mark at 928 International remains to be seen depending on how much metal has been lost in the polishing process that should never have happened.
I'm saying exactly what I wrote back...the arm is fine and there won't be enough aluminum worn off to be of any significance.

Your thoughts on the Powerflex bushings are what they are however the question that Kevin asked was whether new stock bushes could be fitted in-situ and the answer to that one is "no" assuming they have to be vulcanised in-situ. I stated that the Powerflex type bushes could be fitted in-situ if there was some compelling reason why such was absolutely needed bizarre as it may seem to both of us. For sure it was not an endorsement of them. The stock bushings are not vulcanized in place. They are a press fit. As I said, with the proper tooling they could be removed in place....but it would be dumb.

On the subject of the Powerflex bushes I actually wrote to them and asked their technical department what consideration they made about the point you like to make and their answer was simple- they didn't make any consideration. Yup. No clue. This kind of put me off the concept somewhat. On the other hand as a further FYI one of our friends used the Powerflex bushes and thought they were amazing on both the road and the track. I'd submit that your friend has not pushed the car to the limits....or is not terribly sensitive to understeer/oversteer....because it is way different, now.

Perhaps a more interesting aspect of the lower arm concept is whether the perceived resistance to rotation is an attribute of the design or an unwanted consequence. Given the way alignment shops seem to get it so wrong one cannot help but wonder whether this system is somewhat oddball.Actually, I'd submit that the additional progressive spring rate, from the front rubber bushings, did exactly what Porsche legal department told the engineers to do. It's actually pretty brilliant, for what they were trying to accomplish!

Originally Posted by GregBBRD (Post 17406048)

I'm not going to get very far into this discussion.....much beyond this simple stuff about stock cars needing the proper lower control arm bushings is very proprietary information, to me.
I'm not even going to tell anyone how much "progressive spring rate" is actually "in" the lower bushings...I'm just "warning' that it is significant and should not be ignored.
I have, quite literally, spent the last 5-6 months studying/measuring/testing 928 suspension pieces and figuring out what the effect of each and every single part is and figuring out, in detail, what Porsche was trying to accomplish.

I've also been designing and making pieces that will bring the 928 suspension 45-50 years further along, from when it was designed....a complete "modernization" of the 928 suspension.
The 45-50 year old design isn't capable of complementing the current generation of tires...it was barely able to complement the tire technology changes made from 1978 to 1995.

Originally Posted by dr bob (Post 15717292)

Those bushings are molded in place on the arms, and for the front they are molded into the carrier too. There is no rubbing. In the front carrier, if there's rubbing it means that you need to replace the bushings. In the rear, rubbing means your bushing isn't securely clamped, and it's slipping.

There are some aftermarket bushings mentioned over the last few years, You get to remove all the old rubber to clean metal, and then get the new bushings bonded in place. Meanwhile, Mark at 928 International has arranged with the original manufacturer to have used pieces rebuilt with all new rubber parts made as they were originally. He offers the arm on an exchange basis.

The upper arms are similarly available, and they include new balljoints too, so a plug-and-play installation really. Contact 928 International for details.

Originally Posted by Kevin in Atlanta (Post 17407038)

Ordered a pair of LCA bushings from Mark.