pcburnout

I would only recommend it for those who change tire sizes more often than a women changes her mind.



TRUE! TRUE!

JHardwick

Okay, I'll buy that, because mathmatical calculations will not distiquish between static and dynamic circumference.

Lets take an advertised 35" tire ...........

35 x 3.1416 = 109.96"

If you ran a stagger tape around it, you may come up with 108", 112" or maybe even 110", who knows? All depends on mfg, air pressure, etc

Now take 63,360/109.96 = 576 revs/mile

Now, if this were a solid rubber tire, it would be pretty accurate.

But, dynamically, depending on actual tire radius, air pressure, vehicle weight, etc, this number is over 600 revs most likely.

Try this sometime .............

On a flat, smooth surface with your truck standing still, put a chalk mark on the tire and a corresponding mark on the ground. Roll the truck 10 revs (for simplicity of equations) of that tire (preferrably rear tire) and make another chalk mark.

Measure the distance in inches and divide that number by 10.

Take that number and divide into 63,360 ............................ that is YOUR revs/mile based on tire selection, normal air pressure, vehicle weight etc etc

Oh, I forgot to say that this is due to tire squat ......... yanno, the buldge ........... the rolling radius is smaller than a measured/calculated radius.

DR3500

the pinion factor is what they need to adjust, the dealer where i used to live did it for $40. If you go to your tire dealer and ask for the specs on your tires you should find revs/mile somewhere on it. BFG's website lists it for sure. I have 35 12.5 r17 BFG mud terrains (about a Quarter of an inch bigger than 315's) and they set mine @598. the Larger the tire, the lower the number of revolutions per mile.

Dan_K

Dealer set my pinion today at 603 for a BFG AT 35" He also had to change the tone ring to the middle setting.
This was an ordeal for the dealer, but definatly worth it.
Dealer did it for free!!
DK

JHardwick

DR3500, you got it goin on dude