chewy8000

Ok so most of us have been through everyones alignment DIY's and there is some REALLY good information out there. My question is could the cars upper and lower control arm bushings be replaced with delrin or even sphericals to eliminate the "settle" of the stock rubber? I'm sure it would be super expensive but it would probably handle well and you could jack it up all day long without the alignment changing. It's probably alot more complicated than that. Not having to go through the "settle" period would be worth it to me...

I just enjoy driving the car as much as I like working on it. This process is annoying everytime it's in the air.

Imo000

I'm fairly sure the settling is from the shocks and not the bushings.

chewy8000

I just put Bilsteins and H&R springs in. Would that still be the case? Are the stock struts and aftermarket options the same and have the "settle" factor? The only difference I see in the 928 is the rubber bushings? Maybe it's the geometry of the front suspension that gives it this characteristic.


Quoted from Earl Gillstroms site:

"The PORSCHE 928 has very unique suspension bushings compared to other cars. If you jack up a 928 and let the wheels hang down, the bushings immediately take a "set". When you lower the car back down on its tires and roll the car back and forth to "settle" the suspension, the car will now sit ~1" higher than before it was jacked up. The car will now have to be driven up to 100 miles depending on how rough the roads are to settle the car back down to its proper height. The Porsche shop manual says "after a longer journey or longer operating period".

SharkSkin

Nope, it's not the shocks it's the bushings. Run over a few speed bumps at a good clip(medium-sized so you don't bottom out), do some right-left swerves and hard braking, like on the verge of locked up... you can get the suspension 99% settled in just a few miles this way.

Mrmerlin

I think its a combination of both the lower/upper control arm bushings and the shock bushings

SharkSkin

My understanding is it's just the lower control arm bushings. The uppers flop around pretty easily when disconnected from the steering knuckle.

Also the only way the shock could play a part would be if the lower mounting eye were extremely resistant to turning on its mount. Since it only rotates a couple of degrees between the "Settled" and "not settled" position, I just don't see it being a factor; the rubber can easily flex this much.

One final point, if you loosen the caps over the lower bushings and bounce the car a bit it settles right down. Obviously you don't want to do this unless you are planning to get an alignment soon, but there it is...

Landseer

Maybe help your tire shop to rig a winchdown mechanism.

chewy8000

Exactly. So wouldn't replacing the lower bushings with a delrin option eliminate most of this if not all of it? Maybe Carl has some input since he makes the uppers already. I know he has different hardness options for the lowers but maybe there is a reason why there aren't delrins...

SharkSkin

Delrin is much harder than rubber, maybe too hard for this application. One of the things I do to mitigate this is to use ramps for any service that doesn't require pulling the wheels.

mark kibort

no, most of it is in the shock, some in the bushings. I can jack my car up and down and only have .25" difference. I use H/Rs and koni adjustables which are oil filled.

dont fight it. just drive the snot out of it before you want to do an alignment. simple as that. I dont have to drive as far with my set up.

mk

Gary Knox

I have a road about 1/2 mile from my house that is 2 miles long, and essentially "washboard" surface for 1/2 of that distance. Driving over this road at 30-40 mph up and back and the car is completely settled. If you have something similar nearby, that's a quick solution. Earl G. has ridden with me a few times since his earlier posting, and agrees that it is a solution.

Gary Knox

SharkSkin

You have a completely different spring rate, so I think this is apples & oranges.

hacker-pschorr

Which is specified in the WSM as the proper way to align the car. My shop already has the setup for this.

This is from the WSM for installing the lower control arms:

"Screw in until only 2 threads are visible. Do not tighten to 120Nm (88 fltb) until assembly is completed and springs have settled"

76FJ55

It should be an easy expiriment to determine if the shock produce much of the effect. you could loosen the bolt that goes through the lowe shock eye a few turns (leaving sufficient threads in the nut to ensure it won't fall off) then lower the car back down. If it is the shock this should let it "settle" when the weight is lowered onto the wheels. If it still sets high then you would have to atribute it to the control arm bushings.

Fabio421

I can say without a doubt that it IS NOT the shocks. I have tested both new and used shocks and they will rebound completely within a couple of seconds. Thats without the spring attached. Now imagine how fast they would rebound with a ***lb sping pushing them apart?

The problem is in the bushings. Race cars use poly bushings, metal bushing or spherical bearings. These types of rubber bushings that we have don't allow the suspension to move as freely as you would typically want in a performance car. It's just one more thing to show you that Porsche didn't think of the 928 as a performance car.