Monday, September 19, 2011

Difference in mileage due to tire size change?

I went from a tire size P235/70R17 to a LT265/70R17. The P235 has a diameter of 29.9 and the 265 is 31.6. ( I think that's correct) How many miles will it have actually gone when the odometer shows 100 miles? What difference will it be in MPH on my speedometer? Is there a online chart that will tell me?Difference in mileage due to tire size change?Mesafuzzy has the math down to a science. However, to clarify a point: larger diameter tires result in the speedometer under reading actual speed. So using the 5.3% correction factor: indicated 60mph is actually 63.2mph. Note two things: 1) the speedometer counts tire rpms to indicate speed (usually indirectly). 2) Since the speedometer's original calibration is based upon tire circumference of 29.9%26quot;, a circumference change to 31.6%26quot; will result in more distance traveled per tire revolution.Difference in mileage due to tire size change?Had the same question myself recently......discount tire has a chart on their website with that info....or it might just be easier to give them a ring on the phone and let them look it up for you...:)Difference in mileage due to tire size change?Lets see.....

5280 feet = 1 mile

29.9%26quot; tire = 93.93%26quot; around = 674.5 revolutions per mile

31.6%26quot; tire = 99.27%26quot; around = 638.3 revolutions per mile

5.3% difference, 100 miles = 94.7 miles.

Speedometer error will be the same 5.3%

60 MPH = 56.8 MPH