chewy8000

I think from what Lloyd was saying it's not really machining alot off the A-arms. It's more or less cleaning them up and removing whats left of the rubber and maybe inner sleeve. I've never seen one apart so I can't really make that comment with confidence. I'm also curious why one of the UHMW bushings needs to be split?

The UHMW rods are like $30 for a 2ft. rod

The machine work is definately going to be a majority of the $$$$$

Fabio421

Machine work is billed in a per hour basis. Delrin is extremely soft and esily worked requiring less passes and therefore less time. I think you will be surprised at how cheap it would be to make these.

SharkSkin

Scot has cut-down springs, right? With stock shocks? So the suspension will droop more than on a stock 928 when lifted, so I would expect it to have more settling to do than a stock car when set back down.

G Man

Would these Derlin bushings be servicable? Can they be lubed to extend their service life? I'm not familiar with how this stuff works. Maybe some sort of Polygraphite bushing?

mark kibort

when we cut the springs, the droop didnt increase. that is limited to the bushing friction, or binding and the shock piston travel.

one of the issues could be that with such low ride height there could be less binding due to the bump steer angles of the control arms.

It might settle just as fast, as we could be thrown off because the ride height is lower visually. mine, however, even the new chassis, seems to settle almost immediately.

Lloyd

It has been over 5 years since I made these UHMW control arm bushings. Thinking back...after removing the rubber..... Basically just machine each spindle to clean up the surface and make it round. One side was turned on a large gap bed lathe, thus creating the large radius (see above photos). The opposite side could not be machined on the lathe because the part would not swing through the gap. So the part was clamped to the table of a Bridgeport Mill and was tre-panned using a boring bar. I could not find drawings, but I did have some notes on the diameter of the bushing for proper clamping. Reference my photo of the A-arm: Bushing A is 2.360" O.D. and Bushing B is 2.558" O.D.". These dimensions provided enough clamping force without deforming the bushing. These dimensions may vary with your application.
The inside diameter will vary depending upon what size you machined the spindles. You want to have a slip fit of about .002"-.003". As an added measure of safety, I ran a piece of hardened half inch drill rod through each hollow spindle and capped the ends with a large stainless steel washer. The problem with this prototype design is that it does not have a seal to prevent dirt from entering. I usually wrap duct tape around the outside of the bushing to reduce the amount of dirt that may get in. I have not removed these bushings since I put them on the car 4-5 years ago. The UHMW is cheap and the machining was about $150 if you know someone. I have mentioned this modification to Carl at 928 Motorsports and he was considering it. Also, I braced the two front control arm bushings with a steel bar similar to what Carl is selling. This is a much easier task than what it sounds like.

SharkSkin

Did you measure it? Think about what you're saying here. Shocks "top out" at same location as stock(they ARE stock). Car sits lower on cut springs. So, Total droop is more, QED.

Have you measured the total droop of your system? Any data to indicate that the shocks "top out" at the same total length? If not, you're comparing apples & oranges.

In case there is any confusion re: what I mean by droop: Suspension completely settled vs. car jacked up with wheels off ground -- how far does the front axle move downward from the settled position when jacked up.

hacker-pschorr

Once we get going on these, I'll most likely have a batch made up.

When I start to take apart my lower arms I'll take photos.

Thanks again Lloyd!

90 S-4

This is a great project, another option to consider is to
go to a sealed bearing instead of a squeaky delrin bushing.
I did this back around 2001 ? It was on a very similar application,
it was a front lower control arm on a 3400 lb V8 car, not a 928
but the principle worked.
It worked beautifully and contrary
to what you might think it did not cause a harsh ride.
And being that the bearing is sealed there was no maintenance needed.
If this (delrin bushing thing) turns into a group buy and the price is right,
I'd be interested

hacker-pschorr

I've seen that kind of bushing option for other cars, haven't really looking into it for the 928.......yet

Few other options are also floating around up here. Cabin fever is setting in, need to keep the brain working!!!!

BC

Joe - those look BMW-like. True?

90 S-4

Brendan, yes, they went in this car >> http://s296.photobucket.com/albums/mm180/OC570/

mark kibort

do we really want a zero friction system? seems like it would be tough to damp with the shocks. there is a ton of damping in our system that we as racers, tune around. I bet, if you did all near 0 friction fittings, that you would, at a minimum, need 4 way adjustable Motons or JRZs.
If our stuff didnt work so well, Anderson wouldnt have such an easy time keeping up with $200k cupcars on steroids.

90 S-4

On a 928, I'd think that there would still be so much unsprung weight
that it wouldn't be an issue.

BC

Called it! Nice, V8 5 series.