A max-rate turn as I understand it is >60degrees (I think about 75 degrees in the Robin I fly) - full power, and turning on the edge of the accelerated stall. It's "max rate" because there's no power to turn harder. Get it right and you can do a 360 while feeling the stall buffet and then bump through your wake. Good fun
(edit: looks like ASI just beat me to it
and for spelling
)