I've been taking my daily driver R57S to the track latey and have been having a blast!

Suspension:
Stock S springs
Bilstein HD shocks
TSW X-brace
Eibach 19mm RSB on stiffest setting
free front camber mod (locator pins removed and struts pushed all the way in)

Alignment:
Front Camber -0.8
Front Toe 0
Rear Camber -1.0
Rear Toe 1/16"

I feel that I'm still understeering. Before the next track day, I plan to get IE fixed camber plates to get approximately -2.0 front camber. Would this likely overwhelm the rear alignment and cause a lot of oversteer? I am looking for neutral handling. With -2.0 front camber, should I change the rear camber to -1.5 or keep it at -1.0?


Aftermarket springs are out of the question, as I don't want to deal with possible vibration issues that have been reported, not to mention I would probably scrape up the TSW x-brace. Although, I would go with JCW springs in a heartbeat, if MINI ever decides to make some specific to the convertible.

 

Although on an R53; I run -2.0 camber with a little toe-out in the front and -1.5 camber with zero toe in the rear. I have a 19mm rear sway bar set on stiffest.

This is a pretty neutral setup. I have not had this setup at a track day but I did a high speed auto-x (3rd gear turns) and it was neutral with a slight tendency towards oversteer. For a track day I would start with the rear sway bar on the middle or softer setting and adjust stiffer if needed. With -2.0 front camber and the adjustable rear bar you should be able to dial in the handling you like.

I do have JCW springs with a little lighter car so your handling will be a little different.

I have tried a 22mm rear bar and thought it to be too much with -2.0 front camber. 19mm bar is just right.

 

Neg 2-3 deg camber in the front will work much better.

 

I wouldn't expect it to take you too far into oversteer land.

The camber will help your outside front grip mid corner to corner exit once the car leans over and sets. Too much might make it hard to put power down coming out of corners, because don't forget the inside front will be leaning the wrong way.

There are inexpensive rear swaybar options that can dramatically or not so dramatically reduce push. These should help reduce push starting right after initial turn in all the way through corner exit, too much might make the car a little spooky on hard LR transitions.

You might also want to try reducing the rear toe. I run 0, and like it very much. This will help everywhere, most notably in slower turns where you have a high wheel angle. I tried negative rear toe and did not like it - it was unnerving to have the rear sort of wandering at speed.

You can also play with tire pressures a little. Every tire has a "perfect" pressure that maximizes your contact patch. More pressure and the tire bows in the center, less and the tire can roll over onto the sidewall more. Either will give you less grip on that end. Also consider that a tire is part of your suspension, and a higher pressure tire acts like a stiffer spring for the very initial part of compression. Some of your push, especially if it's late in a session, may be from your front tires having too much pressure. Check them right after you pull off, and bleed them to where you want them. Take note of what they drop to when cold, and you know where to start on the morning of your next track day.

I had a guy who road raced Mustangs tell me they started races with their rear tires a 18psi - but after the out lap they would be up to 36psi.

Regardless, I'd do one change at a time and take notes. That way you know if something suddenly is way wrong just to hit "undo" once.

 

Amen,

Cheers,

Charlie

 

About staggered wheels and tires on a FWD
https://blog.tirerack.com/blog/bens-...heel-drive-car
Comment from discussion:
Wednesday, August 15, 2018 byITEM9

On my Honda CR-Z, I run a 245/35R17 up front with a 195/55R15 in the rear, all are Toyo R1R. This setup has been incredible and the balance is pretty much neutral, but still has a slight tendency to understeer, which means it's not dangerously tail happy. So many advantages to doing it this way: minimal rotating mass in the rear, more rear tire compliance to compensate for the torsion beam suspension, rear tires get to temperature more quickly and of course a more favorable front/rear grip balance. Highly recommended.


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Some key items- Wider front tire and wheel with narrow rear tire and wheel is possible as long as there is room for the wide setup in front with no rubbing. Tire diameters need to be equal and a bit of testing for handling balance needs to be done to get predictable and controllable oversteer with track/autocross use. One consideration is that FWD cars may tend to lift the rear inside wheel on hard turns leaving all the rear weight on the outside tire- therefore having enough tire when this happens and driving so that three wheeling is kept to a minimum could be important.


FWD racing
https://www.roadandtrack.com/motorsp...-drive-racing/
https://jalopnik.com/how-to-be-fast-...lai-1795906825

Rally driving- the Basics (see FWD racing)
http://www.oldrallysport.on.ca/articles/Driving.html

I have done Rallycross with my R53 MCS, I put true Rallycross tires on the front and snow tires on the rear giving much more grip to the front drive axles and limited grip for the rears but better than all season tires which I have also used. The sidewalls on the rallycross tires are super stiff and don't flex, the snow tire sidewalls were very soft as were the treads. the thing about rallycross is you are on many different surfaces with each run and course conditions keep changing so one tire may not always work well. Picking the right driving line on the less chewed up portion of the course can be a good strategy.

 

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