radius. however it was supposed to be in mm not cm.
so I’m out by a decimal point above.
I’m getting 2200 RPM at 30in diameter to match the Panda.
Edit: apparently I pulled two versions of the same formula. the one above needs radius in mm. the one I posted in Delta Separations CUP - #5 by cyclopath uses radius in cm. just to keep you on your toes 
actual radius on CUP 15 is about 13.75in. CUP 2.0 hits 1800rpm. Need actual radius on Panda.