Don Juan

My 2 cents since I researched a lot when ordering my 20s and tires and got lot of input from people here
Just as a reference , factory tires and diameters in sport models
Factory Sport #
245-45-18 D: 25.72"
275-40-18 D:25.58"

Option#1 :
easy to get, not too expensive , many brands to chosse from and best compromise. this will raise your overall diameter by 1" and will make the car look a bit higher
245/35/20 D:26.75"
275/30/20 D:26.50"

Option#2:
These will raise another 1/4 inch diameter (meaning a bit taller) in the rear. Some people in this forum opted forthis choice as it makes the tire a bit wider.
245/35/20 D:26.75"
285/30/20 D:26.73"
ps:285/25/20 is too slim and risky as simply thre is not ebough rubber to protect the rim plus in my opinion seems to small for the E60 rear look overall

Option#3:
another size some people opt to get as it maintains the original factory diameter. With this setup you have to have to have the correct offset otherise it will rub. This setup has a nce wide tire in the rear, little sidewall but not too skinny BUT they are EXPESIVE, hard to get and not too many brand choices to look from.
255/30/20 D:26.02"
295/25/20 D:25.81"

Hope this helps