I just up-sized from 17"'s to the following: Fronts 8.5x18 ET 30 with 245x40x18 PS4s. rears 9.5x18 ET 35 with 275x35x18 PS4s. Need to compare to what is on the car now.
One site to look at. Lets you compare side by side.
https://www.wheel-size.com/calc/
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2011 35i BMS High & Low side OCC, Custom tune, CDV delete, Eldor coils, ER Charge Pipe w/Tial BOV, ER Comp. FMIC, K&N drop in,40W LED Halo, LCI side markers, M-Factory LSD, NGK plugs, Racing Dynamics strut brace, Stubby, Windrestrictor