Ended up going with Pirelli Sottozero II winters in 245/35-20 all around.
The diameter is the same in front and 0.01% different with the rear...the load ratings are within BMW spec for the front and rear axle as well.
We'll see how they do with the first snowfall....might be a little sliding but I'll look cool doing it on 20's !!! lol
2013 650i Gran Coupe xDrive M-Sport
2011 BMW S1000RR
2012 535i xDrive M-Sport
2007 X5 4.8 is
2008 550i M-Sport
2007 530i M-Sport