+Tire Diameter 4 Better Look/Lower RPM

[DSAviate]

Just bought a set of used style 87s. Had them evaluated and "spun" at an independant wheel shop - OK. Now looking at my tire options.

I'd like to address a few issues with my new tires . . . for looks, I'd like to fill in a some of the large clearance between our 29.1" tires and the fender . . . also want to reduce the high rpms of my 5speed.

Check out the pic of one member's use of 285/50 R20 tires on page 138 and 139 of "Show Us Your X" thread. His tire diameter is 2.03" more than standard issue on our E53s, 31.13"!! And he claims to have no issues, don't know how long he's been using this setup on his 200k+ miles X.

So, a few questions for the incredible knowledge base here:

1. Is the large clearance between tire and fender necessary? For seriously stressful off-roading, I imagine so. But some here have lowered their E53s and maintained 29.1" tires in widths of 275+, thereby reducing this space and clearance. The gentleman above filled the gap with larger tires. At what point would one expect to run into inner fender tire rubbing in tight turns with normal street driving?

2. Larger tires = Lower RPM. 31.13" tires have a 6.9% larger circumference than our stock. At 80 mph, my rpm could be reduced from 3800 to 3535 with this larger diameter. I know this would affect the OBC estimates for mpg, range, etc. . . . but are there any damaging repercussions if the OBC is NOT reprogrammed for the new diameter?

3. Transfer case considerations - With staggered 87s and directional tires, the tires will stay in place for the life of their service. I'm towing a 5987# load and anticipate more wear on the fronts than the rears. Would it be prudent to find a tire combination for the set that starts with a SLIGHTLY larger diameter in the front? Thus the fronts could wear down to equal diameter . . . and then only approach a diameter disparity limit when the set of four is due for replacement . . . ideas?