Originally Posted by
danr1
I can see why things are all based on 45mph but where rim size comes into play I'm still kinda at a loss. Ford uses 1.33" for tire mash under the weight of the truck, that doesn't change the amount of rubber in tread surface that has to be covered each full rotation. The rim could be any size within that same circle but what da heck do I know! lol
I was wondering that also.
I have never worried about changing the constant even with 15 years of ownership.
Just yesterday I checked constant for the first time and I was shocked.
Going to calculate correct # and change mine too.
Not to throw another formula or method out there and possibly confusing someone, but couldn't you mark the length of a tire revolution, in inches on your driveway and take the results and divide into 5,280' (63,360") to arrive at the revolutions per mile?