determination of aero vs. mechanical grip

I have a track dedicated e46 M3 with a significant front splitter and rear wing, limited undertray of the car beyond the front splitter. Curious how I adjust the suspension setup in this course (i.e. ride height, lateral weight transfer calculation) based on the additional aero downforce being achieved, focused primarily on mid-turn, medium to high speed corners.

Basically you start with getting the handling / balance correct in low-speed turns (30-40mph). If you can use a skidpad this can be ideal. This will be the mechanical grip balance, and you adjust the springs, anti-roll bars, rake (ride height different front vs. rear) and tire pressures to achieve balance. It's important to get this right first, or the aero will be fighting an unbalanced car.

Next observe how the car handles in high-speed turns (90mph+) -- this is the aero grip region. Now you can adjust the splitter depth, ride height and wing angle to achieve the balance needed to carry maximum speed through high-speed turns.

You may also wish to introduce some sort of travel recording. The ideal is a sensor for each wheel's travel/compression, but tie-wraps on damper shafts can give a basic check on compression under bump, cornering and/or earo' loads. A very basic check is a dab of grease, or grease paint, on the compression stops that will witness if the suspension has bottomed out. The last is often the cuplprit for a high speed twitchiness on bumbier corners, or even straight line.