285/30/20 is 26.7" tire diameter
https://f30.bimmerpost.com/forums/sh...2&postcount=85
widest i've seen on an f30/32/36. 295/30/19 +45, 26", i believe h&r sport. the tires are 0.7" shorter and have 0.35" less sidewall than 285/30/20.
https://f30.bimmerpost.com/forums/sh...&postcount=201 ...285/30/19(25.7"), +40 offset, unlowered. tires 1" shorter and 1/2" less sidewall than 285/30/20.
since you're lowered the tire shoulder will tuck in a little however its 26.7" height maybe be an issue. it'll be tight.