540I versus M5 tire size

[jeffnlexi]

Why is it that the E39 M5 has 275/35/18 tires with no rubbing but my 540 rubs, could it just be the aftermarket springs only, fenders rolled, are the fenders different?

J

[98M3_4]

M5 rear fender lips are already stamped flat, unlike non-M fender lips. The M5 rear wheel liners also allow more clearance than the non-M liners at the very top and upper sides.
I'm not sure what your wheel/tire setup is, but your lowering combined with that setup may require you to roll the fender lips. Wheel offset, tire size and how much your lowered are the keys to fitment.