Fixing the rear geometry once and for all...

[e304me]

while in the market for suspension for the GRM, i had that idea of rocker geometry open game as motorcycle components are easy to come by and rebuilt relatively cheaply/easily. i already have some sketches for component design in that regard, in case you want to discuss that topic further.
But thats all second hand to what has to happen first, the suspension arms and frame.
What about a trailing arm from stock subframe (Groupe-A style) for lower-front a-arm, a cross bar from equal distance perpendicularly for lower-rear, and the upper arm mounts perpendicularly to the trailing arm from under the car's frame. ..the geometric complexities from the resulting setup makes my head spin :)
lets work with a different car that already has this suspension, eh?

that seems like it could work, if you could get the lower rear a arm to be in a position to keep toe constant through the travel range. seems like that would be damn hard though

[e304me]

whats this grm you guys are talking about

[matt]

How much of a benefit? A lot.

Will the car be as fun to drive? Who cares, if it's faster.

GRM = www.grmotorsports.com

The only way I can see doing this is to use two a-arms mounted to a new rear subframe around the diff. 2 A-arms and a fixed tie rod to control rear toe.

[e304me]

you may be able to barrow parts from the ultima gtr, although it seems like it may be a dated design. The car holds like 1.15 gs on the skidpad on street tires but it doesnt have much body roll.




we should also look at lowering the front control arms outer mounting point to bring back some of the camber gain. I wonder if the inner bushing would fit in place of the outer bushing? that would make it easy as all you would need is a special spacer and a welder.

[matt]

I already have a solution in the prototype phase for the front end. Results will be posted as they become available. (This will be installed on the WR car.)

[Mike B.]

From Gustave's site...



If you can create something like this, with CAB's around the same size as the Treehouse racing one's - count me in!

[Mike B.]

we should also look at lowering the front control arms outer mounting point to bring back some of the camber gain. I wonder if the inner bushing would fit in place of the outer bushing? that would make it easy as all you would need is a special spacer and a welder.

You can already do that for $150.

[matt]

You can already do that for $150.

http://gsperformance.com/products/rc-spacer/pic-2.jpg

Those only work with M3 struts, not standard e30 ones. My solution will work either way. (and for e36s also)

[e304me]

does it require welding? just make sure that shits strong enough

[Mike B.]

Matt,

Yep, you're right M3-only (works for me though :)). Still really interested in what you come up with though.

If you haven't already, check Gustave's site, LOTS of good suspension info there. Should help in avoiding some basic pitfalls before you start fabbing.

E304me,

The spacers are bolted into place with aerospace grade hardware - should be strong enough.

[e304me]

oh i was talking about the one matt was making. I wish that setup worked for regular e30s!!!

[matt]

I am not going to sell the roll center and bump steer spacers or anything... they will just be for the WR car.

The setup I'm playing with for my own car will probably use e30 M3 struts with a spacer like Gustave sells. I am very familiar with his site, BTW.

I have a couple of suspension guys who are current and former LMP engineers helping with the project, so I think I'm in good hands.

[e304me]

aww come on man why not? are you planing on selling the rear suspension?

[matt]

Only installed at our shop, if it ever comes to that. It will be outside the budget of most r3v-ers also.

The complete 5-lug swap/A-arm rear suspension with all the special tricks would probably run $6k.

[Mike B.]

Only installed at our shop, if it ever comes to that. It will be outside the budget of most r3v-ers also.

The complete 5-lug swap/A-arm rear suspension with all the special tricks would probably run $6k.

You forgot to add at the end of the first sentence - But would be willing to sell to other shops for installation on the shop owners car... :D

It sounds like the project is in good hands.