Here is the way to hand calculate your Revs Per Mile (the most accurate measurement). This is not my idea, I'm just passing the info along as it was given to me.
Originally Posted by Bcarriveau
I know alot of us use the calculators out there to figure out the number for the sct or rely on the tuner to figure it out from tire size... well they are off. Lonnie brought this to my attention.
After correcting the number the shifting got alot better then what it was..
Here's the simple way if you don't already know how..
Put a mark or piece of tape on the 6 o'clock position of your tire(side of it) and then make a mark on the ground next to it(starting point) , roll the truck forward or back one full turn so the mark is back at the 6 o'clock position again. make another mark on the ground. Now measure how far apart the 2 are in inches.. mine was 99"
There are 63360" in a mile..
so 63360/99 is 640 thats how many revs per mile the tire will make..
Iv been putting in what the calculator told me and that was 617.. Tires are 285/70/17s.
Yah that's a bit off now isnt it..
Go try it out for your self it really made my shifts alot quicker and nicer. only took my 2 years to learn this
Ill add there was never any problems but this made a change that i like.
If a Moderator could please make this a sticky, I would greatly appreciate it, as I have gotten a ton of PM's asking for this information.