in KingBobDole's example above the tyre circumfrence changed from
3 feet / revolution to 5 ft/rev,
so,
the speedo thinks 1 mile equals 333 revolutions,
but,
333 revolutions actually equals (333 x 5) 1.666 miles,
so,
the speedo thinks 1 Mph equals 333 Rev / hour,
but,
at 333 Rev / hour you're really doing 1.666 Mph,
so,
at 100 Mph on the speedo you would be going 166.6 Mph!!!
because,
there is some error intoduced for EACH revolution,
so,
the more Rev / Hour you're doing the bigger the error!!!
166.6Mph in tha Brumby = some scary S__t!!