Understeer Solutions? Sway Bars?

[Dimman]

We really need to get something down on roll rates and camber curves.

It can help quantify how much of an effect each has on keeping the tire where we want it.

[7thgear]

i'm sure someone's modeled the car in 3D, it wouldn't take much work to make some internet friendly animated gifs.

but they'd want $$$ for it..

[SubiePig]

I just got a copy of Lotus Suspension Analysis yesterday. I plan to tackle this when I get a chance.

[Wepeel]

I've done the math on the camber change as a function of steering angle, caster, and SAI. I'll post up the results.

Camber change as a function of bump/droop - I don't think there's anything unique about the McStrut geometry on the twins - I've seen a few of those curves for Imprezas, if we don't have the exact geometry of the twins we can probably use the Impreza curves as an approximation. There is camber gained during bump (more than non-trivial), just not as much as what you can get from a wishbone/multilink.

[7thgear]

do these models take into account axial body roll and resultant change in the relative position of the suspension pickup points as a result of weight transfer?

[SubiePig]

Originally Posted by 7thgear

do these models take into account axial body roll and resultant change in the relative position of the suspension pickup points as a result of weight transfer?

The software is able to do all of this, just have to learn how to work with it.

[7thgear]

[CSG Mike]

Originally Posted by Dimman

We really need to get something down on roll rates and camber curves.

It can help quantify how much of an effect each has on keeping the tire where we want it.

This isn't exactly what you're looking for, but in our experience, this is our observation with Street tires (RS3, Z2, RE11A, etc) with a -1.5ish drop all around for track used based on wear and pyrometer readings:

12k front springs need roughly -2.8 camber
10k front springs need roughly -3 camber
9k front springs need roughly -3.3 camber
8k front springs need roughly -3.5 camber

14k rear springs need roughly -2.3 camber
12k rear springs need roughly -2.4 camber
11k rear springs need roughly -2.5 camber
10k rear springs need roughly -2.6 camber

These results are based on our observations with multiple Tein SRC and JRZ setups, and are for maximum grip under track conditions, which gives you anecdotal evidence that can be extrapolated into camber curves. As always, YMMV, and this is very, very crude data.

[Dimman]

Originally Posted by CSG Mike

This isn't exactly what you're looking for, but in our experience, this is our observation with Street tires (RS3, Z2, RE11A, etc) with a -1.5ish drop all around for track used based on wear and pyrometer readings:

12k front springs need roughly -2.8 camber
10k front springs need roughly -3 camber
9k front springs need roughly -3.3 camber
8k front springs need roughly -3.5 camber

14k rear springs need roughly -2.3 camber
12k rear springs need roughly -2.4 camber
11k rear springs need roughly -2.5 camber
10k rear springs need roughly -2.6 camber

These results are based on our observations with multiple Tein SRC and JRZ setups, and are for maximum grip under track conditions, which gives you anecdotal evidence that can be extrapolated into camber curves. As always, YMMV, and this is very, very crude data.

Stock bars?

[CSG Mike]

Originally Posted by Dimman

Stock bars?

Yup, stock bars.

[7thgear]

Originally Posted by CSG Mike

Yup, stock bars.

do you think static camber requirement would have changed had the height remained at OEM levels

[CSG Mike]

Originally Posted by 7thgear

do you think static camber requirement would have changed had the height remained at OEM levels

I honestly don't know, since I don't know the camber gain/loss curves under compression. Those numbers above are what is necessary with our setup, and is only meant to be a single data point; it's hardly conclusive.

[Wepeel]

Originally Posted by Wepeel

I've done the math on the camber change as a function of steering angle, caster, and SAI. I'll post up the results.

Camber change as a function of bump/droop - I don't think there's anything unique about the McStrut geometry on the twins - I've seen a few of those curves for Imprezas, if we don't have the exact geometry of the twins we can probably use the Impreza curves as an approximation. There is camber gained during bump (more than non-trivial), just not as much as what you can get from a wishbone/multilink.

Okay numbers are posted here, because it seemed like it should be it's own thread.
http://www.ft86club.com/forums/showthread.php?t=48107

[BRZ RN]

Originally Posted by CSG David

Are you running square spring rates? That alone will induce some understeer. Your alignment should also fix some of the issues as well. Most setups dial in understeer for safety purposes.

what's the recommended spring rates? i out of the box KWV3s