225/45-16.....If it was ok for Alpina, and German TUV, and the E30 M3 2.5 Evo, and all that jazz, it'll be fine for your use. Any wider in my honest opinion will be too wide, leading to poor tracking on anything other than smooth pavement, possible loss of grip due to too much contact area on a lighter vehicle, and definite traction loss in the wet.