Hi, guys. Can someone tell me if it is possible to downsize to 18" rims? The thing is my X5 has 20" 214 tires with 275 40 20 front and 315 35 20 rear. I want a new set of rims to do some light off road and winter driving, this 20" wheel set perform bad as soon as you exit the asphalt . Some people say the 50i has larger rotors and calipers than the 35i so the smallest rim is 19"...