mrr23

Read some people wondering about this. So? I decided to take some measurements and see the results. This was on a subaru wrx.

First picture is straight ahead. Second picture is about 10* left and third picture is about 10* right. Person sitting in car.

Also notice how much the toe changes as well.

Solofast

This is the effect of caster increasing camber as you turn the wheel. The WRX has a modest kingpin angle so your negative camber is increasing as you steer.

With higher kingpin angles eventually you will lose camber as you go to higher steering angles. Would have been more interesting to measure at higher angles and on a car with more kingpin inclination. At small steering angles the kingpin angle doesn't make much difference since it is a sinusoidal function. At higher steering angles it can predominate. On the later C4's you could feel the grip go away as you cranked the wheel past a certain point.

mrr23

Next car that comes in, I'll try to take measurements at 20* as well. Can't control SAI too much.

flash911

What I've learned ...

You are correct in that you can't control SAI / KPI at all unless you swap them out for fabricated units. Vette spindles have between 8.35 ~ 8.65 KPI. I say between because I have seen both measurements and not verified myself (I emailed Lou G about this once, but only got as far as confirming his road race spindles match factory KPI specs).

Three things you can do to control camber gain to your advantage under compression:

- get those control arm bushings solidified, Watch the Pfadt vid on utube for evidence.
- start with your LCA level or pointing up .5 - 1*. This will start your camber from negative to more negative as you compress your front suspension in a turn.
- KPI / Caster split. Try to get 1 - 1.5* of caster above your KPI. This will keep your contact patch as flat as possible under compression as camber increases.

I do not know what the factory camber gain per inch is. I have measured on a fabricated front suspension using C6 components (similar, yet different mounting control arm points) and found .5* per inch. On that car I started with -2* camber and 2.5 inches total compression for a little over -3* total.

mrr23

next corvette i have in, i'll try to remember to take SAI measurements.

davidfarmer

Set you castor to zero and this problem will go away. Of corse so will your handling and steering feel!!!!!!!

mrr23

per request i did a 20* left/right measurement today on a c6 z06.

mrr23

did some measuring today on my own car for reference. what i am going to show here is how much difference there is measuring whether you are sitting in the car or not. i am 215 lbs

first up is me out of car

straight ahead


10 left


10 right


next up is me in car

10 straight


10 left


10 right

mrr23

this is how much difference there is when adding 215 lbs to the driver seat.