Well, I measured an RA1 and an R888 static unmounted and here are the results.

RA1 bead to bead measurement is 9.25", section width is 10.5"
R888bead to bead measurement is 10.0", section width is 11.25"

Those of you right on the cusp of track width beware...you just gained 3/4" in track width... I know I will be illegal with all of my current wheel inventory that clears my brakes.