I need some help on getting tires for my 20's. I currently have iForged Daytonas 20" matte black with a polished lip and need to get new tires soon. The current tires are rubber bands and I need tires with a bigger sidewall and want to know what size tires you guys are putting on your M5 with 20's. I had thought that for every inch the rim goes up the sidewall profile has to be reduced by 10, does that still stand true? So 285/35/19 should change into 285/25/20 or am I wrong? Someone help.