Breyton wheels has an 8.5 plus 9.5 wheel combo. Their wheels are 41 or 42mm in the rear depending on which model you choose. They recommend 225/40/18 all around. Or no bigger than 245/35/18 in the rear. I don't know if these figures are for stock suspension or not.
1995 325I, tinted windows, K&N, debaffled air box, BMW style #104 wheels, Nighthawk low beams, smoked side markers, smoked corners, smoked taillights, M3 style heated mirrors, various interior bits, Bosal cat-back