tire question

im looking to buy new wheels for my 2007 530xi, i have not herd good things about 20" wheels on this car, so im thinking of going with 19" now if i do that what size tires will i need to keep some what of a good ride?

I have a 2007 550i and I went from the ugly 17 inch stock 225 50s to a staggered 19 inch 275/35 in the rear and up front I have 245/40s. Unfortunately the fronts rub a little on big bumps with the suspension. (no issues with turning) I'm super careful and it's only happened a couple of times. A 235/35 should clear the front suspension though unless you use approved spacers then you could probably go with a 245 up front.

The ride is noticeably stiffer but not too stiff.