285/35/20 for E70?
 

I am looking at the new Vredestein Ultrac Vorti tires for my X5 - seems like a great tire from all I've read.

The only problem is the closest size (to stock fitment) would be 285/35/20s.

I would do a square setup on a 20"X10" wheel.

The 285/35/20 has a smaller circumference and diameter compared to a 315/35/20:

Circumference Comparison
285/35/20 - 87.5 inches
315/35/20 - 90.1 inches

Diameter Comparison
285/35/20 - 27.9 inches
315/35/20 - 28.7 inches

Speedometer Error
At 90MPH the actual speed would be 87.5 MPH

Has anyone tried this? Do you think the size difference is too great?