Hey,

Posted this in the Aftermarket Chips/Tuner forum but only 16 people viewing. Im out now testing this and data logging and had a friend ride next to me. at 70 mph he was having to do 77 to keep up,

So his truck is stock, and Im thinking Im off 6-7 mph.

I have 265/70/17's

The best I can come up with Im turning about 638 Rev's a mile. Can someone dbl check me on this and make sure Im accurate!

Thanks
Tom

 

your calculations are off.

I am running BFG 35" KMII's an have my tuner set to 625 revolutions/mile and read 1/2 MPH off against a GPS speed reading.

 

check tirerack.com find your tires, look at the spec page, and it will give you the TRPM

Im going through this right now because i went to a smaller then stock tire.

 

5280ft / [(tire size in inches)*(3.14)/12]

This formula should give you revs/mile

 

Section Width: 10.43 in 265 mm
Rim Diameter: 17 in 431.8 mm
Rim Width Range: 7 - 9 in
Overall Diameter: 31.60 in 802.64 mm
Sidewall Height: 7.30 in 185.42 mm
Radius: 15.80 in 401.32 mm
Circumference: 99.27 in 2521.4 mm
Revs per Mile: 658.2

 

265/70/17

265 = 10.433 inches
* 70% = 7.303 inches for sidewall height
* two sidewalls is 14.606"
+ 17 inches of rim = 31.606" in diameter

so your circumference is 99.244 inches.

If every mile is 5,280 feet or 63,360 inches

Your tire goes around 638.4 times in a mile.

--

Of course that assumes that your tire really measures 265/70/17. Sometimes they're bigger or smaller and only the manufacturer knows.

 

Check this out.

http://www.discounttiredirect.com/di...TireMathNS.jsp