Rear Toe/Camber Options

[Lurker27]

So I been readin' this site:

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

And it occurs to me that, instead of eccentric bushings or camber correction subframe kits, why don't we just raise the TA mounting points (rip out, add steel, weld in new) equivalent to roughly whatever the drop is?

You'd maintain the best part of the camber/toe curves by bringing the rest position of the suspension back to nearly horizontal.

Am I crazy? Failing this, are the correction kits superior to eccentric RTABs?

[Lurker27]

While I'm here, is this feasible for the E30 Subframe bushings/Diff mounts? I can't tell if the E30 ones are hollow at all like the e28...I guess new bushings are so cheap it's not even worth it though.

Looks like it: http://www.turnermotorsport.com/imag...gpnrsfm_lg.jpg

http://www.flickr.com/photos/fritz_da_kat/4187025020/

http://www.tycksen.com/bmw/tech/flexane/index.php

[Wh33lhop]

I believe Massive Lee was selling a kit awhile ago to raise the rear subframe for exactly this purpose.

[jlevie]

It would seem to me that the hard part about raising the trailing arm pick up points would be doing it in a manner that resulted in equal camber and correct toe. Small errors in the placement of the new tabs has a big affect on camber and toe.

Between eccentric bushings and camber/toe correction kits, the latter wins hands down. The eccentric bushings tend to drift out of alignment and getting camber and toe correct is a real pain since the adjustments aren't independent.

[Lurker27]

Good point. It seems like the weld-in tabs would suffer that fate a little, too. So, correction kit + Poly RTABs is the trick setup then?

[whodwho]

There have been discussions on raising the subframe to do this by flipping the bushings upside down. Massive is making solid bushings ones and looks there are some poly ones available now that do this with more offset.

http://www.akgmotorsport.com/catalog/catalog.php?page=3&category=New%20Products

[nando]

raising the subframe is not new.. BMW did it way back in the E30 M3 DTM days. 12mm, and it does make a good difference in toe/camber.

funny how a lot of "new" parts/ideas these days are actually recycled stuff from the early 90's..

[Lurker27]

raising the subframe is not new.. BMW did it way back in the E30 M3 DTM days. 12mm, and it does make a good difference in toe/camber.

funny how a lot of "new" parts/ideas these days are actually recycled stuff from the early 90's..

You'd just think it would be more common, since it decreases suspension binding compared to the other solutions...but there is no commercially available solution for it now.

[nando]

look in the post above you..

[Lurker27]

Ah, good stuff. Thanks. Anyone running those?

EDIT: At this point I might just let search run its course

[surebimmer]

Good info. Didn't know AKG had ploy bushings that would raise the rear. I'm going to do this soon.

[Wh33lhop]

funny how a lot of "new" parts/ideas these days are actually recycled stuff from the early 90's..

I don't see how this is a surprise; we don't really know anything more relevant nowadays than we did back then, which was also when people actually cared about E30s, as they weren't 20 year old shitboxes.

[g22]

Can someone explain how raising the subframe changes things? I'm missing something and not able to visualize how this works.

[Lurker27]

Basically, you have your alignment settings at some value based on the position of the trailing arms at some distance away from being straight back off the subframe (parallel to the ground)


When you lower the car, the arm is already at an angle pointing UP off the ground, which also increases negative camber and toe in. When the suspension compresses under load, you'll gain even more negative camber and toe in, to the point of having too much. You can change the static setting (but retain the portion of the camber and toe curve you're on) by using the weld in subframe fix or eccentric trailing arm bushings.

Raising the subframe, on the other hand, is basically anti-lowering from the standpoint of suspension geometry (but retains the lower CG benefit). You totally shift the position on the camber curve, so your static camber and toe are closer to stock, and the camber and toe-in gain under suspension compression are closer to stock.


With respect to wheel motion, the camber gain is linear, so the effect is the same. However, by raising the subframe, you'll get less dynamic gain in toe-in compared to correcting with the weld-in fix.

I'm not sure which is faster in practice. Some toe-in is desirable to plant the rear in cornering.

[g22]

When you say raising the subframe do you mean moving it away from the car, essentially spacing away from the body?