Whiteline told me their roll center correction kit (KCA435) doesn't affect camber

[Pat]

I was hoping this kit would decrease the amount of camber loss as my suspension compresses, but they said it does nothing of the sort. An email I got from an employee of Whiteline in California said, "So I got word from my AU office that these actually don’t affect camber static or dynamically. This is purely for making sure the toe stays true to the alignment while cornering." This is surprising and disappointing to me. I understand that isn't the primary goal of something like this, but with a Mac-strut front end, I would think camber loss through suspension compression would be less with a kit like this.
I feel silly second-guessing what Whiteline themselves say this kit does, but what do you guys think about this?

[wparsons]

Primary focus is to correct roll center and bump steer (two different things). As a side effect they do put the LCA's into a better location so you have a slightly better camber curve at the same ride height. I don't know how much the balljoints are extended, but it should put it back close to stock if you're lowered an inch.

[maslin]

If the LCAs are level at right height camber will increase as the shock compresses. Below level, the camber will decrease until the point that the arm crosses level, then increase.

Lowering the arm in relation to the spindle will help, although probably not a huge amount.

[jamal]

I mean, technically there would be a change, as you are moving the suspension to a different part of the camber curve, but it's going to be very small.

And how do you know that you are losing camber as the suspension compresses? have you seen a plot of camber vs bump? Due to steering axis inclination I'm pretty sure there is still negative camber gain past where the ball joint and inner pivot are level.

[Pat]

Originally Posted by jamal

And how do you know that you are losing camber as the suspension compresses? have you seen a plot of camber vs bump

I guess I don't know for sure. I have not seen a plot of camber vs. bump. Can anyone here confirm this or provide data?
I am lowered about an inch from stock. I am really curious to know much more camber I have (if any) at maximum lateral acceleration with the KCA435 kit than without it. The first guy I spoke with at Whiteline in CA estimated .5* to .6*, but after I pressed him for data his confidence seemed to dim, at which point he kindly emailed the guys in Australia for a response. I would LOVE to see .5* more camber at maximum lateral acceleration, but based on what you guys are saying that seems improbable.

[maslin]

Going off this post:

http://www.ft86club.com/forums/showp...&postcount=175

Camber switches to gain at 1" of bump, where you are sitting now. So anything will help, but it's really going to be marginal.

[Pat]

Hah! I just saw the exact same post and was coming here to share the link. But I'm not sure I understand the chart. I think I understand the shape of the line. Basically, the first part of the suspension travel creates camber gain, but past a certain point of bump travel, it stops gaining camber and starts losing camber. I think the BRZ gains camber up to 1" of bump travel, then starts losing camber. And because my ride height is 1" lower than stock, I basically lose more and more camber as my suspension compresses more and more, right? I'm just having trouble understanding the units of this chart. How much camber is lost from 2" from stock right height? 3"?

[maslin]

Originally Posted by Pat

Hah! I just saw the exact same post and was coming here to share the link. But I'm not sure I understand the chart. I think I understand the shape of the line. Basically, the first part of the suspension travel creates camber gain, but past a certain point of bump travel, it stops gaining camber and starts losing camber. I think the BRZ gains camber up to 1" of bump travel, then starts losing camber. And because my ride height is 1" lower than stock, I basically lose more and more camber as my suspension compresses more and more, right? I'm just having trouble understanding the units of this chart. How much camber is lost from 2" from stock right height? 3"?

Yes.

Chart is for stock height, compression runs across the bottom.

For the first inch on compression the camber goes more negative, to a max of -0.2* at 1" of bump. From there the camber increases, at 2" of bump you're back to where you started, at 3" you're 1* positive of starting.

Since you're lowered 1", you LCA is flat sitting still. All positive camber from that point on. At 1" bump you gain 0.2*, at 2" bump you're 1.2* positive of the starting point.

Cut it all off, multi link it and move on

[Pat]

SUPER helpful, maslin. BIG thanks.

[maslin]

I had some wonderful scheme in my head, but this is what Paint gave me. Black line is the imaginary line between the inner LCA bushings and the top of the strut. Red is the strut/spindle, blue is the LCA.

[ZDan]

Jamal has it right. Camber goes more negative until LCA goes past perpendicular to axis formed by top of strut and ball joint. I.e, well past where LCA is horizontal.

Imagine the illustration above but where the blue line representing LCA actually stays the same length! Instead of getting radically shorter at the bottom...

[maslin]

Originally Posted by ZDan

Jamal has it right. Camber goes more negative until LCA goes past perpendicular to axis formed by top of strut and ball joint. I.e, well past where LCA is horizontal.

Imagine the illustration above but where the blue line representing LCA actually stays the same length! Instead of getting radically shorter at the bottom...

I tried. And you’re right, it’s when the angle between th LCA and strut goes past 90*. If the strut were straight up and down it would be when the LCA is level.

It’s the LCA relative to the strut, not the ground, that matters.

[jamal]

There is a really old plot of an sti front camber curve that looks like the one posted above



And for a long time I took it as accurate. But I think that both curves are only considering the motion of the lower control arm and not accurately modeling the strut travel.

There is a company or two that has modeled the suspension of these cars, but I believe you have to pay them. I really should have done it myself a long time ago (for other subarus I mean, which all have basically the exact same front suspension).

Here is a guy who actually stuck an angle gauge on his hub and jacked the suspension through it's travel.

https://legacygt.com/forums/showthre...es-266122.html

It's a legacy gt, so a little different, but if the above curve for an sti I posted was accurate, it should be close. But it's not. The curve is actually closer to a straight line where negative camber increases all the way to the bump stop. Like I mentioned, this is because the strut inclination is pulling the top of the upright inward, even as the control arm is going past level.

[maslin]

Originally Posted by jamal

There is a really old plot of an sti front camber curve that looks like the one posted above



And for a long time I took it as accurate. But I think that both curves are only considering the motion of the lower control arm and not accurately modeling the strut travel.

There is a company or two that has modeled the suspension of these cars, but I believe you have to pay them. I really should have done it myself a long time ago (for other subarus I mean, which all have basically the exact same front suspension).

Here is a guy who actually stuck an angle gauge on his hub and jacked the suspension through it's travel.

https://legacygt.com/forums/showthre...es-266122.html

It's a legacy gt, so a little different, but if the above curve for an sti I posted was accurate, it should be close. But it's not. The curve is actually closer to a straight line where negative camber increases all the way to the bump stop. Like I mentioned, this is because the strut inclination is pulling the top of the upright inward, even as the control arm is going past level.

I spent too much time trying to make a 2d CAD drawing that proved the chart. Keeping control arm and separation the same, decreasing the length of the shock an inch at a time. Camber kept decreasing until I got to an excessive bump travel, 5" or so.

I deleted the file and the app, since it had to be wrong. I guess it was right?

It should add negative camber until the LCA/strut break 90*, right? Sadly, the front struts are basically perpendicular to the ground, not a ton of angle to work with. It's the line from the top pivot to the ball joint, but that's not a huge angle.