rangerruck

Let's say for sake of argument, you don't change your gears/tranny any.
If you get tires that are 2 inches taller than WHATEVER you are currently running,
even if they are allready taller/aftermarket than the factory tires, to get the mileage off of your odometer- for every 12 miles you drive, add another mile for mileage. Does this sound about right? Is this close? Does anyone have some real world experience with this?

I have a call in to b.f. goodrich, on mileage on tires, that are only 2 inches taller or less, than the factory size tires, but a person of ill qualification to answer, called me back, to clarify. Finally she says, she will have to pass along the info to one of their engineers, so I am waiting on that call...

rangerruck

...okay, I get it. that is like a reversal, of the other way to figure it out exactly; i was just wondering if there was a general rule of thumb. So if you added a mile for every 11 or 12 miles driven, and if you have a 15 gallon gas tank, and can go 300 miles, that would be adding an extra 27 miles, which is not exact, but it is fairly close...

but I like knowing the exact way, better.

alfio

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

go there, it will give you the exact differential percentage versus your factory equipped tires. then all you gotta do is the math (+/- whatever percent)

alfio

ayoung101

the equation for the perimeter of a circle is 2 x pi x radius. you can do the math to get the perimeter of each size tire, and that will give you a length ratio for each tire revolution. not that you'd count the number of tire revolutions, but you can use that same ratio to figure out the new distance. (for example, let's say the ratio between the 2 tire perimeters is 3/4, or .75. if you went 100 miles according to your odometer, you actually went 75 miles).

or, a much easier way to do it, drive on the freeway for 100 miles (according to either your odometer or the mile markers, your choice), and compare it to the other #. that will give you the same ratio without doing the math.

rangerruck

all good ideas, plus if only the height of your tire is changing, without diameter of wheel, you should be able to go new height/old height x distance= % of distance traveled.