No Calibration Needed!
 

Ok, I went from 32's to 35's and I have been trying to figure out the exact number of my MPG. But here's my theory - so my mpg is off 3 inches, larger tires are making less revolutions per mile which means I'm going a bit farther than a mile when my odometer shows I went a mile. I think it's a great thing as far as warranty wise. :D :D

Re: No Calibration Needed!
 

Here are my calculations:

32's - 630.6 revolutions per mile

35's - 576.5 revolutions per mile

so, 630.6 minus 576.5 equals 54.1, which means 54.1 less revolution per mile for the 35's. Not much but it will add up...:D

Re: No Calibration Needed!
 

Re: No Calibration Needed!
 

Sounds wrong, but just keep good records so you can let the DMV know the odometer isn't accurate before you trade it in and you should be fine.

Re: No Calibration Needed!
 

You should also calculate how it effects your speed, as the speedo will also be off as well. You'll be going a bit faster then reflected by the speedo.. so watch out for speeding tickets.

32's - 638.6 revolutions per mile - ~8.6'/revolution

35's - 576.5 revolutions per mile - ~9.15'/revolution

My math says its about 6.6" diffference per revolution difference so
for every 638.6 revolutions (1 mile on your odometer) you've traveled 9.15 feet on the 35s or 638.6 * 9.15 = 5843 feet or 1.10 miles. Roughly an extra 600 feet.

Edit: Assuming your revolutions are correct...

Re: No Calibration Needed!
 

So, do you have other way to calculate it? Already tried the dealer if they could calibrate it but they can't do it. And I don't think I will trade it in...:D

Re: No Calibration Needed!
 

So for every 1056 miles you will save one mile on your odometer so if you average 12000 miles a year you'll beable to hide or save about 11.4 miles I gues it does kind of add up.
-But have mpg gone down?
-stayed the same?
-or gotten better?
-do you know?
-and what tires andwheels do you have?
-Oh and one more question what air pressure do you run them at?
Sorry for all the quetions but I'm trying to decied if it is worth going from the 33's to 35's thanks.

Re: No Calibration Needed!
 

I used this furmula to figure out - C = 2 pi r for the circumference. They are 63,360 inches a mile. Maybe I could be wrong...:D

Re: No Calibration Needed!
 

Just enjoy the better look and overall wheelability, and don't sweat the small stuff!
~11miles...your gonna lose that in wheel spin in a years worth of offroading anyway!:D

Re: No Calibration Needed!
 

That part is correct, but I think your closer to 1 extra mile for every 10 miles on the odometer. I don't know how you get 5 feet for every 1 mile on the odometer, if I am reading your second post correctly. Not exactly sure what you are saying in that post.

Re: No Calibration Needed!
 

with my calculations, 35's revolves 576.5 in a mile... and 32's 630.5, ... :D

Re: No Calibration Needed!
 

yeah, the 5 ft. was wrong. 54.1 less revolution a mile on the 35's comparing to the 32's..thanks. :D

Re: No Calibration Needed!
 

Too much math...my brain hurts! :D

Re: No Calibration Needed!
 

x 2.5 / 4^7 :D

Re: No Calibration Needed!
 

Use this calc...

http://www.miata.net/garage/tirecalc.html

Re: No Calibration Needed!
 

Ok the math is killing me to but just because I needed to figuer it all out so here it is. And yes I have a touch of OCD at times :D

32's: Cir=100.48" Rev. per. mile=630.57

33's: Cir=103.62" Rev. per. mile=611.46

35's: Cir=109.90" Rev. per. mile=576.52

and 1 mile = 63360"

So 33's will: Get you 1 extra mile for every 32 mile compared to 32's

and 35's will: Get you 1 extra mile for every 10.67 miles compared to 32's
and 1 extra mile for every 16.5 miles compared to 33's

sorry but I had to redo the math for my own sanity. lol...

Re: No Calibration Needed!
 

there you go!!.......and deiTai.. good find on the tire calc. :D

Re: No Calibration Needed!
 

All this math and there is an easier way. Just use your GPS, or borrow one.:D

Re: No Calibration Needed!
 

What, my math wasn't good enough for you? :D

Re: No Calibration Needed!
 

Don't forget that 32"/33"/35" tires aren't really that size. You should go to the mfrs website or tire rack to get actual dimensions.

here's an example for tire rack & BFG AT KOs, 35" is really 34.5"

http://www.tirerack.com/tires/Spec.j...rrain+T%2FA+KO