We started setting up my wife's 07 Mini S when it was still in G-stock and never really got very far. She wants to keep racing it on street tires and we're ready to buy some suspension parts along the lines of STX prep. Luckily she's not racing it in SCCA so we're not stuck with the exact rulesets for STX.
The car is stock with the front camber maxed up with factory adjustments, Koni yellows on factory sport springs currently. We'd like to get an aftermarket spring setup that will encourage a more neutral balance (car understeers too much). Also interested in a larger rear swaybar to achieve the same thing. What are the popular parts out there to achieve this? Is the 19mm rear sway large enough or is something like 25mm required? The car is still a daily driver primarily and autocrossed on the weekends for fun.

1. What size/brand rear swaybar? Solid or hollow?

2. What spring setup to cut some of the body roll, encourage a more oversteer bias?

3. Camber plates?

4. What size wheel/tire either in 15, 16, 17 diameter and what size tire? Can you fit a 15X8 6UL wheel over the Mini S brakes? Would a 225/45/15 tire fit?

 

Camber plates - Vorshlag is my choice of camber plates

I think that the OEM brakes are too large for 15's, although, could be incorrect. If it were me, I'd get the Willwood 11.79"(I think that is the size) brake kit for the fronts to allow for 15's. Either that or go with 17's since there is a selection of 17" tires in the 235/245mm width. If I were to run STX I would certainly test fit a Toyo R1R in 245/35/17 on an 8" or 9" rim(9 inch might be tough to find). Optimal setup would require shaving of the R1R since they have a good bit of tread squirm unshaven. I also think the Hankook RS-3 might be a good choice. If I remember correctly, I think the Hankooks like heat(you would want to research this) so that might be an excellent choice for the Texas summers.

Not sure on the other questions as I have been away from the Mini scene for a couple years. If I were to go with a different spring setup, of course, my choice would be AST coilovers.

 

Thanks, may look at 17 instead of 15 route. Vorshlag is just down the road from me so that's a consideration. Thinking about changing the rear sway first and then springs and then wheels tires. Right now just running on the factory 16" star wheels with some 215/45/16 Kumho XS.

BTW I ran against your old car last weekend at BMWCCA with the new owner Jeremy, very close race against my Elise