I made that change at one point and the new tires are 4.3% bigger. At 60
mph on the speedometer I was actually going about 62 mph.
Doug Fedeli
Seth Hollander wrote:
> Ok this may sound really stupid, but my truck came
> with 215/75/r15, now I have 235/75/r15, what is my
> percentage difference...no onehas messed with my
> computer. I wonder if I am actually getting better
> mileage than I think. -Seth
>
> --- Jason Yates <onebad4x4dak@yahoo.com> wrote:
> > OK . . . you've got me wondering here. My truck
> > came with the
> > 31" tires (so the CABS should be set to 689 already
> > right?). I
> > changed to 32" when the bad-years wore out. I
> > haven't had the
> > computer flashed or anything. I thought my mileage
> > would only
> > be off by the difference in percentage of
> > circumference between
> > the 31" and 32" tires which is like 3.1%.0 If what I
> > am reading
> > here is correct, the real difference is 9.3%? I'd
> > appreciate
> > the confirmation.
> >
> > Thanks,
> > JY
> >
> > --- Ronald Wong <ron-wong@home.com> wrote:
> > > Nothing to do with trig. Just good ole fashioned
> > geometry.
> > > The difference
> > > around the outside of the tire is called the
> > circumference.
> > > Circumference =
> > > diameter X pi. The tire revolutions per mile is
> > the number of
> > > times the
> > > tire rolls the length of the circumference. If
> > you have a 32"
> > > tire you are
> > > right in your calculations. That percentage is a
> > whopping
> > > 9.3%.0 The next
> > > time you calculate your mileage, multiply the
> > mileage your
> > > odometer says
> > > you've gone by 9.3 0x1.f727070616e55p+871nd add that figure to the
> > total because
> > > that's how far
> > > you've actually gone. Divide that by the number
> > of gallons of
> > > gas you used
> > > for your MPG. This all presumes the dealer
> > flashed your CABS
> > > to 689.
> > >
> > > Ron
> > > 00 PB SLT QC 4X2 5.9 46RE 3.92 LSD
> > > For modifications see my DML Profile (URL follows)
> > >
> >
> http://www.twistedbits.net/WWWProfile/dakota/Kw9pV1EkFeOYY
> > >
> >
> >
> > __________________________________________________
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> > Yahoo! Auctions - buy the things you want at great
> > prices
> > http://auctions.yahoo.com/
>
> __________________________________________________
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