Running NITTO Dura Grapplers 275/70/18, also using a X3 tuner which requires 'revolutions per mile' for tire setting. This tire comes out to be 608 rpm. The X3 settings are in 5rpm increments. Is it possible to figure the setting to include the "3% 'squish' factor" with this set-up ? Or is it even possible with this unit ?

 

with 3% it should be 617 rpm

 

Set it at 610 and you will be good. After you hit 40 or so mph its out the window on rpm anyhow.

 

If it's revolution per mile data from the manufacturer, it already has "squish" factored into it. Just enter it into the programmer.

 

Obviously that is not the manufacturer's published rev per mile data. I just looked it up on Nitto's site and it's 625. Just plug that in the programmer and you're good to go. 608 x 1.03 = 626, so you must have used the published O.D. in your 608 figure.

 

i used the pegasus calculator to figure it off of the given tire size, and it came to to 617. i used the same calculator for my truck just with a 5% squash and it dead on with both gps and local pd lasers.

 

Thanks for all the help guys !! I got the 608 figure from another tire sizing site...I'll plug in the 625 and call it a day !

 

A good website is www.powerdog.com plug in your tire size and the results will be close....

 

Sam, to fine tune it, compare the programmer's speed readout with a GPS, if it can monitor vehicle speed.

 

I also have a gryphon I am using just as a gauge pod at the moment and a GPS. I plugged in 820 with the X3 and between all three (speedo, Gryphon, GPS) everything was within 1 to 2 mi difference with each other and on occasion they were the same. As stated Thanks Again folks.