Autocross Tuning: Effect of Rake

I used this event as a test-and-tune to play with rake on my 2007 Mazda RX-8. I have adjustable coilover sleeves, which allows me to set ride height. i had been running about 1/4" lower in the front than the rear, i.e. +1/4" positive rake. The RX-8 naturally has a higher rear roll center versus the front, and this leads to a steep roll axis. This tends to enhance front end grip and reduce rear end grip. My car has always felt a little loose, almost everywhere, but especially during aggressive trail braking and during high speed transient maneuvers like slaloms.

For this event, i started the day with my typical +1/4" rake (about 13.50" front hub-to-fender and 13.75" rear-to-fender distances). As expected, the car was pretty loose and made it tough to attack the course with full aggression. During lunch break, i jacked up the car and spun the rear spring perches down one turn, which results in a ~1/8" ride height reduction. This resulted in a more modest +1/8" total rake. The results were transformative for such a small change. I hope you enjoy the video comparisons!

This event was captured at the MBCA Autocross (Solo) event #5 at Summit Point Washington Circuit t on 16 July 2023. This is a great venue that offers lots of runs and lunch time tuning opportunity.

New settings:
13.50" front 13.625" rear ride heights
Max front camber, max front caster, zero toe
Rear camber matching front, +1/32" total rear toe in
25F / 23R tire pressures (hot)

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#512 Mazda RX-8 Summary
32mm front swaybar, redrilled OEM rear swaybar on stiff
Custom bilstein / ohlins / aftermarket frankensuspension
AEM intake (STX modded), underdrive pulleys, Versatuner
Fujitsubo catback exhaust
Kumho V730 265/35/18 on 18" TSW Nürburgring wheels

My data acquisition setup:
   • Full autocross / track telemetry | 25Hz GP...