new rims - offset for 18x8.5?

whats going on everyone,

i am thinking about putting on some 18x8.5's on my e36 m3. the particular wheels i want to get come with a few offset choices of 15, 30, or 40mm. i don't know much about rims and tire sizes, and which match together well, so i wanted to ask if anyone knows which combo would be better...

- 8.5's with 245/40 all around
- 8.5's with 235/40 all around
- 8.5's with 235/40 front, 245/40 rear
- or maybe drop the front down to 7.5 & 8.5 rears (w/ 225 in the front?)

1. will any of these combos rub either when turning the wheel all the way, and/or with a drop?
2. is fender rolling needed?
3. will i need spacers?

any and all recommendations or tips are appreciated. or if anyone has a better setup for 18's, that would be great.

thanks alot

tk

Don't know much about what your m3 will take but you're definitely asking the right questions per rubbing et al. My son has a jeep with oversized tires and needs to beef up the rear as when all seats are full the tires drag against the plastic extendo-fendos. Bummer and more expense.

By the way, if your old rims will fit a 93 325i and selling is a consideration, keep me in mind.
Good luck on fitting your wheels of choice.