I love your work that rear end is not going anywhere!
This is something I have seen a lot a lot of people do without realising the Consequences. When you lower ride height plus lower the crossmember the lower trailing go from angling down to straight or even worse angling upwards.
They angle down for a very good reasion. It is called roll centre What happens as the control arm moves up during compression during Cornering this forces the wheel outwards, the opposing force resists the compression reducing body roll. If the control arm is flat or angling upwards the wheel moves inwards during cornering compression and induces more body roll.
If does not make any sence just google roll centre for a better explination.
My suggestion would be to lower the engine in the car without moving the steering rack and control arm mounting points.
You can get roll centre adjusters for wrx's that move the tie rod end and ball joint lower but not a much as 2" and they are very expensive.
I am actually making custom front control arms for my brumby(brat) that mount higher and further out on the cross member and spacers for the tie rods so i can adjust out the bump steer and my crossmember has only been lowered 1/2"
Ps You can get plenty of negative camber with adjustable strut tops or lengthened control arms.
I am no stranger to suspension tuning
and everything you say is correct, but the are a few items I have not yet set up in the suspension that will fix some of these problems.
The rotary is significantly taller than its subaru counterpart, even the distance from the oil pan bottom to the crank center line is significantly larger on the rotary than the subaru. In order to maintain the low CG I am keeping the rotary under the hoodline. There is no way to get the engine lower without fouling the steering rack, as it is I have ~5/8in between the rack and the oil pan.
The FB rx-7 front suspension is the same basic setup as the sube, just mirrored front to back (rx tension links are forward, instead of rearward to the tranny mount). In the rx world we use offset roll center adjusters that space the suspension arm down by bolting between the ball joint and hub. Towards the end of the project I will be milling these out. The other consideration is that the legacy wheel/tire combo has a significantly larger rolling diameter so I wont be lowering the front suspension as much anyway.
Next year I will be swapping in the Legacy front suspension, which by my measurements gives me almost an extra inch to work with as far as oil pan clearance goes. This leaves me with only 1in of subframe spacers, and custom roll center adjusters to set the arms where I want.
All in all this car will spend most of its life slammed and sideways, so the spring rates will be very stiff, and likely large sway bars added to the mix.
thanks for the comments
its always nice when someone spots a potential problem.
Edited by flight_of_pain, 21 December 2010 - 01:05 AM.
I R can spel gud?