Long story w/a question at the end. I had a formula for figuring my actual miles traveled and thus the real MPG's, but I don't think it's right. So does any one have the formula for converting the percentage of the difference between the stockers (265's) and any other tire sizes you want to plug in. Which in turn will help w/ speedo corrections. Not as fun as talking about turbos, but it's kind of important. Thanks

 

Just compare the published revolutions per mile of the stock tire with the replacement.

 

Interco (super swamper) say's it's a 5mph increase per every 2 inches over. If you're just trying to get an idea how fast you're actually going. 265/70's are apx. 32". So, with 33's you'd be going 2.5mph faster than what your speedo says. Or you could just by a Smarty and adjust...

 

Old tire diameter divided by new tire diameter would give a number less than 1 if going from smaller to taller or more than 1 if going from taller to smaller. Multiply the product by the odometer reading for actual miles travelled.
Or you could take it up on the expressway and run it for 10 measured miles and see how far off the odometer is. For example, if your odometer reads 11 miles, you're 10% off.

 

Try this link it has a conversion chart just plug in the oem to the new.
http://swatt.j.porter.name/tech-cent...ire-calculator
Hope this works

 

265x70/2540x2+17= 31.61" Stock tire diameter.

Now then: Your new diameter tire/31.61= 1.?? the amount to multiply your speed by. This is how fast you went. Or how far you went if you multiply by your tripometer distance.

 

By the way....The stock Michelins are spec'd at 31.41. Thus the stock setting showed the speedo going a little faster.

 

Try this link for the difference in tire sizes and speedo.

http://www.1010tires.com/TireSizeCal...bmit&reset=yes

 

Thanks for the formula Inferno. Now, does anyone know the exact diameter of toyo 285/70/17? Is it exactly 33 or slightly bigger 33.something?

 

Errr never mind firemansdodge link gave me what i need I was posting the same time as him.

265 diameter = 31.6
285 diameter = 32.7

 

Gentlemen, Thank you, I did know how to figure the speed. Part of the problem is that the web sites with numbers you plug in, don't allow for tires with standard sizes, i.e. 35's,and some sites would come up w/different speeds, which made me question their formulas. Interestingly enough 35's are 10% off from stock, by that formula, some sites said 9%, others more. This is a great site! Lesson? Do the math yourself,and know!! Thanks Inferno, and thanks all for contributing