The RPF1 has always been a very light wheel for the size. I think they make that step because the shorter perimeter of the smaller circle is both stronger and needs less material.
At least that's what my brain came up with. That step is a real annoyance for everyone but the guy mounting the tire.
-Dan
"Capitalization is the difference between helping your Uncle Jack off a horse, and helping your uncle jack off a horse." "'she' also likes to swap since I think I am going to need to give her to woody again." - Dvlhntr "full alphabetic boost mode" - ChristopherTheOne " Purrs like a sexually satisfied black panther." - BigTDogg "Two oil eating, angry, spinning triangles of death." - turtleboy on rotary engines