Rear Suspension Pics Needed - Not a 'Show your drop' thread

[tinkwithanr]

Hey R3v,

I'm currently in the middle of installing the e30 rear subframe and suspension in my '75 2002 body (build thread in sig) and I need some help. I want to make sure that the position I fabricate the mounts in will leave the trailing arms in the correct position with respect to the subframe at my desired ride height. After a few hours searching around I've come to the conclusion that no one ever takes a picture of the underside of their car while it's on the ground (loaded suspension), go figure.

Basically I need someone with a close to stock ride height (not slammed, messes up the geometry to much) to snap a few pictures of their rear subframe/suspension and their angles in relation to the ground.

Something like this, but with the wheels sitting on the ground and the suspension loaded at a normal ride height:





If anybody has a picture like this already or would be willing to take it for me it would be greatly appreciated!

[AndrewBird]

Your ideal position would be level trailing arms at normal ride height. Any change either way starts to mess with suspension geometry and characteristics.

[tinkwithanr]

Really? I mean I understand how the camber and toe change as the arms sweep up and down, but from what I've mocked up so far it seems that 'level' trailing arms have a LOT of static negative camber. It appears that the wheel hub assembly is angled off of the trailing arms, as opposed to being perfectly in line with them (which would give zero camber with level arms). It looks to be around -4 or more degrees. I really want to find the angle that will give me around -1 degrees static so that I will have a range of 0.5-2.0 degrees overall once I install the adjustable link mounts.

Thanks again guys, I'm sure someone out there can help.

[nando]

Really? I mean I understand how the camber and toe change as the arms sweep up and down, but from what I've mocked up so far it seems that 'level' trailing arms have a LOT of static negative camber. It appears that the wheel hub assembly is angled off of the trailing arms, as opposed to being perfectly in line with them (which would give zero camber with level arms). It looks to be around -4 or more degrees. I really want to find the angle that will give me around -1 degrees static so that I will have a range of 0.5-2.0 degrees overall once I install the adjustable link mounts.
Thanks again guys, I'm sure someone out there can help.

why don't you just do it that way instead of going off a picture?

the camber curve is pretty linear. I'd read all of this:

http://www.e30m3project.com/e30m3performance/tech_articles/susp-tech/index.htm

http://www.e30m3project.com/e30m3performance/tech_articles/susp-tech/rear_curves/index.htm

[LJ851]

Your ideal position would be level trailing arms at normal ride height. Any change either way starts to mess with suspension geometry and characteristics.

Sorry, this is not true.

You do not want this in the rear because of massive squat under acceleration, especially with the power OP is planning on putting down.

[tinkwithanr]

why don't you just do it that way instead of going off a picture?

the camber curve is pretty linear. I'd read all of this:

http://www.e30m3project.com/e30m3performance/tech_articles/susp-tech/index.htm

http://www.e30m3project.com/e30m3per...rves/index.htm

Thanks, but I already went through his site. While the camber curve is linear, the graphs on his site are only for the change is camber angle, not the actual measured camber angle with respect to the ground. I could do that fairly easily if the spindle axis was in the same plane as the trailing arm mounts, but it's not. And since I don't have a way of accurately measuring static camber right now, I was thinking basing it off the stock setup would be the next best thing.

[LJ851]

Why don't you just put an angle finder on the hub to determine your camber angle ?

[tinkwithanr]

Don't have one at my disposal right now.

Worst case scenario I'll just order one, but I was hoping to knock out some of the fab this evening.

[mikeedler]

here's a few of my car ON the allignment rack. yes, it is lowered, but probably only about 1" lower than stock. hope it helps a bit even though it isn't the compete rear.
I have camber/toe adjusters installed, and in the pic, it has almost all of the camber dialed out of it ( so where it should be at a stock height car, I think it was just a tad over -1 degree .

[tinkwithanr]

Great, that's just what I was looking for. Thanks!

It also confirms my thinking that the trailing arms are angled down in their static position (even on a lowered car) while the axles are at a slight upward angle.

I'll have to see if I can borrow an angle finder (good thinking LJ851) from one of the local machine shops to double check everything. Together I think that should get it pretty dead nuts on.

Thanks again guys

[AndrewBird]

Why not just go by one of these? They are cheap.



And my previous comment was a generalized, best case scenario for any car, not specific to e30's.

[tinkwithanr]

That's the last ditch option. but an option none the less. Not really as accurate as I would like (hmmm, is that 1.25 deg or 1.75 deg....) but it could work in a pinch if I need it to. I would really prefer a digital readout, helps take human error out of the equation a bit.

[e30trooper]

i only got this

[Vivek]

[tinkwithanr]

Thanks guys!

Vivek - Any idea if that's a stock suspension or lowered at all?