You could run a 235/60r17 size tire if you want more sidewall. This is the size I use for my summer setup.
I wouldn't go below 29 psi on the front tire pressures and 32 on the rear as per the BMW manual recommendation.
Even a 225/65 r17 can work for a skinnier and taller tire. This is the size I use for my winter setup.
I should clarify that I'm using 17"x8" wheels.
Also, if you search on Michelin's website for example, it will show the safe "rim width" for each size tire under specifications.
If I look at Michelin Pilot MXM4 in 235/55r17 size it shows the safe rim anywhere between 6.5" and 8.5"
Last edited by mlukas161; 11-15-2012 at 07:22 AM.