good info! I might be tempted to even put a super tbin coat of rtv between them

Did you smooth/polish the bolt?

 

Yes, I did. Soon after I installed the the powerflex LCA bushings I cut 1 coil off the front and 2 off the rear springs. As most know, coil count is just as important as wire diameter when it comes to a springs rate. GB brings up an interesting point, for some reason, perhaps by design, the Lower control arm rubber resists twisting and some consider this resistance contributory to the total spring rate of the suspension as a system. That seems reasonable. I see it a-bit differently and I stress my previous use of the word resistance. Read on for some more details and observances.

Any one that has tinkered with just the OE bushed lower control arm alone bolted to the frame with no spindle can observe this resistance when moving the control arm by hand and with a jack. I found the movement odd, slow and resistive. Didn't think much of it and wondered to my self it needed to be this way. I was thinking about the back end of my Jaguar and how it seemed so clear and communitive. Perhaps it 's the fact that the Jaguar's suspension uses roller needle or tapper bearings at all major motion joints. This allows the suspension to move up and down with great precision and ZERO resistance. I dreamed about some thing like this for the 928 that would allow the suspension to move like this.

I did a bit of a test with the OE setup... I removed with front sway bar, went for a brisk drive and what I overserved surprised me. With the sway bar removed I pitched 928 over with a hard twist of the wheel and it leaned hard as expected, BUT when I straightened out the wheel, it stayed leaned over for a moment as if there was something holding the car in its pitched over position. There was, those awful lower control arm bushes and now I could observe what they do dynamically becasue the 928's rather thick front anti-roll bar was disconnected. I would characterize this slowness to reaction as resistance which not only is contributory to spring rate but also very dulling and produced an un-natural feel through the steering wheel and oddly delayed body motions. Not wat I wanted. We know the LCA bushings do this becasue if you jack up a 928 it take some time to settle. It was at this moment I knew the power-flex LCA bushings and a some more spring rate was going to be transformational for the dynamics of a 928. The first time I dropped my 928 off it's jack stands with the power flex LCA bushings installed it went right to it's natural ride height. Then I went for a drive and I was stunned how different and clear the steering and body motions felt. I was no longer driving through mud. The ride quality was so much better than I expected so I thought my tire pressure was low but it wasn't. Few if any other modern cars use the 928's LCA bushing arrangement and I suspect this is the reason why.

 

That means the bushing was bad.

Every observation past that was based on bad data.

Put new ones on there..and stand on it.

It can be done..different springs/etc...and I dont wanna walk into the cut-spring debate, that has a special place on the internet to discuss it.

But A linear OE spring with the progressive resistance of the OE bushings, will be incredibly hard to reproduce.

Springs for this "fix" are cheap, but you'll spend _thousands_ on shocks to make it work right..the way it all works OE.

IMHO _few_ people really understand how this car was meant to feel when it was new, without a massive overhaul of the OE suspension on new OE parts (and while you can still get them the M474 shocks)..and then assess.

But people are doing..for the most parts, 1/3 of the work, and claiming something else is better.

 

You could probably win a trophy for fast typing.
ive wondered about the diffetence in behavior if bushings are used it don't grip on both sides. My instincts tell me that you want free movement in those bushings and leave it up to the shocks and springs to do what they do but if these were engineered factoring in that rigid grip.... would you need a lower rebound rate in your socks and the stiffer spring rate to compensate?

 

Whats neat, is the front LCA bushing is multiple layers of stainless and rubber. It has a lot of torsional resistance inside it because of this. It's not just 'a' piece of rubber that has a single thick band to twist in.

 

My LCA bushings might or might not have been bad, but even new LCA bushing take a set when jacked and I think its this effect which causes the dullness, resistance, delay and unwillingness to react.

I don't see it this way, there is no way for you to know that the LCA bushing were bad and not operating as designed. I would characterize the observations as empirical, real world, valid and illuminating.

No need to reproduce this effect, no modern car uses this system for a reason. It's dulling and tire technology has improved so much that even track focused tires like Cup 2's are livable as summer daily drivers.

I don't think of the OE LCA bushings as a progressive spring. After the sway bar test I see them more like stuck on "friction shocks"

It's not about lap times, it's about driving dynamics, feedback and feel. In this case its more about the joy or connectedness of the driving experience. Yes that COULD translate into lap times. but as we both know a good driver in a poor car can be faster than a poor driver in a good car. Good drivers adapt to the machine, poor drivers blame the machine.