So I recently picked up my first mini a month and a half ago.

This is Ava. My dinky, old, leaking 221K R53.



Well along with whatever I am working at to repair, I am also considering a few little mods. I am trying to figure out what is the most wide wheel I can run on a stock R53. Ideally id like to run 17x8 RPF1's with 225/45. I have the 17" white 7-8 spoke wheels with 215/45 PSS that I put on, and it seems to work well but I want more stick so I can utilize the power the car has better.

Would it be safe to run a 17x8, and if I can, what offset is required and what tire size is required?

 

Not sure of the offset but from what I know, (which isn't all the much), anything more than 8 inches wide and there will be rubbing issues. Get some Pilot Sport PS2 tires. Just about the stickiest street tire you can get and still get "some" tire life.
https://www.tirerack.com/tires/tires...ilot+Sport+PS2
If you have the S-Lites, which it sounds like you do, get new wheels, those things are HUGE bricks, very heavy. ANYTHING is better the S-lites.
http://minicooper.wikia.com/wiki/OEM_Wheels_and_Tires

 

I run 15x8 949racing, I think +35? with 225/45/15's for autocross/trackdays with jcw springs I had to run 5mm spacer in the rear to clear trailing arm. Fronts fit without spacers but they really need 10mm to look right. I could easily fit more front tire on with this combo.

On my track r53 with KW v3 swift springs, I have to run 10mm spacer up front to clear the coilover adjusters.

 

I'm running a 17x8 +38 with a 215/40R17 and I rub slightly under full compression in the rear.

 

17x7.5 et-35 with 215 40 17, rub slightly in the rear. but it is flush to the arches at ride height (stock ride height)