being that the Gryphon wants the circumference that is 2*pi*radius, so it should come out to about 109.96 inches, which turns into 279.29 cm, which is 2792.88 mm, then times that by .97 gives you 2709.1, but since your gryphon cant do the .1, enter as close to 2709 as possible and you should get a fairly accurate speedometer.
The other way to figure it out is to find out how many revolutions per mile that your tires make and then divide 1609344 (mm per mile) by that number and you should get pretty close to 2709 but with less calculations, kinda like bill says on
this page.
Hope that helps!
