E30 Roll Centers

[nando]

That's awesome. I always though this was an under-appreciated modification. It's simpler than adjustable TA bushings and it doesn't come loose. I only stumbled on it because I found out ix bushings were taller than RWD bushings, and I had installed RWD IE bushings way back when H&R sports were "it".

[Digitalwave]

Just wanted to update this thread, since I got the car aligned with the new parts a few months ago.

With 12mm riser subframe bushings, H&R Race springs in the rear with 1 thick spring pad, and Bilstein Sport shocks, my rear camber was 1.4* on both sides. Hub center to fender lip height is 11.75" (late model rear arches). I don't remember how much toe, but it wasn't bad.

This was perfect as I am limited in front camber by the OEM size spring perch hitting the strut tower. I would like to run more camber all the way around down the road by switching to coilovers/2.25" diameter springs. In the mean time, the riser bushings taking camber out of the rear was a worth-while solution.

Regarding the roll center spacers in the front. I am running 16" Style 4's, and I went with 13mm spacers. I definitely have some room to spare. I think 19mm (3/4") spacers would have worked fine with these wheels, but 25mm (1") would have hit the wheel.

Overall I made too many other changes on the suspension at the same time to attribute it all to the roll center changes. Switched from 19/14.5mm sway bars to 22/19mm, SLR adjustable CABs, and from stock rubber to full Condor bushings. That said, it is a night and day difference on the track. The car rotates better, is more neutral, and has more overall traction than the previous setup did.

[autox320]

^ Beat me too it. I grabbed all the pages and doubled up on the non-broken images and links, just to be thorough.

I had been looking for an non-broken copy of the trailing arm geometry for the past few weeks... Guess my interneting skills are lacking.

https://drive.google.com/open?id=0B0vcza5E5r15U3ZHdUZLYktaYkE

.zip file for all the tech articles:

https://drive.google.com/open?id=0B0...UpJZXBma2xzY0E

I've a pdf copy of the M3 GrpA manual if you'd like to add it to the archive somehow. It has some interesting tidbits in it even though once again S14 specific. Some suspension setup specs. Literally has the entire break down of service for the whole car. S14 peeps request emailing it all the time and not everyone has a copy. PM me an email address and I'd gladly contribute it.

[autox320]

thanks for bundling and link

really one of the best resources for these cars specifically

if interested there are a lot of material references on s14power forum as well ie some 1992 dtm specs and roll cage designs

some have taken the liberty to even duplicate these parts

[lambo]

^ Beat me too it. I grabbed all the pages and doubled up on the non-broken images and links, just to be thorough.

I had been looking for an non-broken copy of the trailing arm geometry for the past few weeks... Guess my interneting skills are lacking.

https://drive.google.com/open?id=0B0vcza5E5r15U3ZHdUZLYktaYkE

.zip file for all the tech articles:

https://drive.google.com/open?id=0B0vcza5E5r15aUpJZXBma2xzY0E

[agent]

Part 2:

[agent]

works for me?

Somebody should PDF the whole site in case it disappears for good.

I did. Some of the images are broken but I think I got all the pages.

Part 1:

[nando]

they've disallowed the Internet Archive from showing that domain, it won't work for anyone

works for me?

Somebody should PDF the whole site in case it disappears for good.

[M-technik-3]

It still works for me, odd.

[agent]

I was able to access it so I did a quick and dirty print of the pages to PDF.

[kronus]

they've disallowed the Internet Archive from showing that domain, it won't work for anyone

[aventari]

I get this "Page cannot be displayed due to robots.txt."

does it work for anyone else?

[nando]

Gustave made great contributions to many subjects long ago. Here is an archive of his page. You can ignore the kmac eccentric bushings :) that's just shows how long ago this was written. Everyone by now knows the trouble with eccentric kmac bushes and how bad they were in the day. Not the same as eccentric adjusters most use today. Plenty of other very good info to reference and what the dtm guys were accomplishing with this chassis. Plenty of S14 specific parts for those interested.

http://web.archive.org/web/200802210...tech/index.htm

yes, I loved that site! Too bad the original was taken down, good thing for the internet archive. Should make a PDF of all his tech articles as they are still really helpful.

[nando]

Think of the trailing arm as a lever with the fulcrum around the spring, which you've noted won't change position. You're moving one end of the lever up 12mm. Since the motion ratio is about 2/3, it would seem the ride height rises closer to 1/4". Either way I definitely noticed it when installing my risers.

the 2/3 motion ratio is the distance from the wheel to the spring in the transverse direction, it's not really the same thing. if you think of the trailing arm like a teeter totter, with the spring being the fulcrum, the distance from the subframe to the spring in the parallel direction is a lot further than the distance from the spring to the wheel (probably more like 1/4 than the 2/3 motion ratio). Sure, it moves, but it's a very small amount.

[autox320]

Gustave made great contributions to many subjects long ago. Here is an archive of his page. You can ignore the kmac eccentric bushings :) that's just shows how long ago this was written. Everyone by now knows the trouble with eccentric kmac bushes and how bad they were in the day. Not the same as eccentric adjusters most use today. Plenty of other very good info to reference and what the dtm guys were accomplishing with this chassis. Plenty of S14 specific parts for those interested.

http://web.archive.org/web/200802210...tech/index.htm