on the "Read SPEED at TIRE DIAMETER" part of the calculator, is the speed read supposed to be your speed at the end of the 1/4, or is it just your speed at the set RPM? instructions are: pull slide to set engine RPM at gear ratio. Read speed at tire diameter. dosnt say if its for est 1/4 or not. my guess is its speed at your RPM only, and up to user to figure the rest.