Auto Racing: SCCA SM Racing, negative camber, spec miata

Question
My son and I race a spec miata in SCCA, we are small budget, out of pocket team.  We started in 2007 and have slowly advanced in competition.  I understand the need for correct weight distribution, but we have a problem setting the car up for different tracks(ride height, castor, toe in/out etc.) if we change any of the aforementioned it changes the weight distribution.  Is there any way to know ahead of time if you change the settings, say you change the toe on the rear, do I know ahead of time what that will do do the weight distribution, if I change the sway bars, soft/hard will i know ahead of time where, if any this will change the distribution?

Answer
Hi Ken!

Thanks for writing.  
Changing the toe out, front camber or castor shouldn't affect the weight distribution, at least not to any significant degree.  I don't have any great "secret" numbers for Miatas, but I think I can get some good advice from a couple of friends should you need it.

Altering the ride height, epecially front to rear will change it, and raising and lowering individual coil over spring heights will alter it diagonally across the car.  Since adjusting the sway bars tends to slightly raise or lower that end of the car it will also affect your weight distribution but very little. If you want to get real kinky you can use assymetrical preload on a sway bar to favor one corner, and perhaps to get some weight off the left front.

If you want to find out what effects are from each adjustment, you can use a weight checker (which I'm trying to catalog without success) which is a $200.00 gizmo you can use on a flat surface to check weights as you work.

AS far as calculating affects beforehand, I think you would spend as much time in calculating as you would just doing the trial-and-error thing. I know of no computer software that does this for you.

Here are some numbers you may wish to try as a base line.

Front:  toe out 1/8" total. Less on a long track like Daytona.
       Negative camber of 2 1/2 deg both sides.
       4 Deg. positive castor and more if you can still turn the steering wheel
Rear:   toe IN of about 1/16" and NEVER straight up, talk about EVIL !
       Negative camber 2 1/2 deg both sides.  Less on the RR if it's light.

Tire temps should be even on the outside and center, and about 10 to 15 Deg.F hotter on the inside.  Get air pressure from the tire guys, and if the center is a bit hot remove about a pound at a time 'til you get it right. On test day, run five laps each time out, then come in HOT for tire temps. Do other adjustments during the breaks.

I'll see if I can find who has the weight checker thing available and send you a follow up answer.

Good luck !

Dan Liddy
Sarasota, Florida