Here's what I know
I have a data acq system and a downloading playback Tach that I've used to
determine Engine Rpm. When I take that engine rpm and the total height of
the tire and multiply them... I get a number that can be divided by 336 and
then divided by the gear ratio and it gives me the TRUE Ground speed in mph.
so it's Rpm X Tire ht in Inch's... divided by 336 divided by the final drive
gear = MPH...
I understand that the tire contact patch squishs the tire a bit due to
weight... BUT when you consider centrifugal force... it about comes up even
with the higher tire pressures I run...
This concept works well both for planning and has given me the exact run
numbers when compared to the SCTA,USFRA and the ECTA timing systems. it's
not off by more then 1 mph ... Sooo if you need to be closer then that maybe
we are working on the wrong thing....
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