Correcting m.p.g. for 285's

[fencebuilders]

I did a search and found tons of info,but not the specifics i need. I am trying to figure mileage as accurately as possible,by hand. I have 285's on my truck and need to account for the difference in tire size. Assuming trip meter was at 550 miles and i fill up 32 gallons that would equal 17. 18 m. p. g. That being said,what is the corrected number?Thanks,Mark.

 

[smithinc]

assuming you had 245/70r17 before, the difference is about 7%.



552 miles plus 7% is 590 miles devided by 32=18. 46 miles per gallon.



gary

 

[jponder]

If you can, use a GPS they will really tell you whats up

 

[fencebuilders]

Originally posted by smithinc

assuming you had 245/70r17 before, the difference is about 7%.



552 miles plus 7% is 590 miles devided by 32=18. 46 miles per gallon.



gary

Stockers were 265's. Thanks.

 

[DF5152]

a little less than 4%

 

[Moterhead]

If you go here:



http://www.csgnetwork.com/tireinfo4calc.html



and plug in your two tire sizes, you will find



265/70/17 RPM = 638. 1 and

285/70/17 RPM = 616. 6



subtracting one from the other, you get 21. 5

that's the difference in RPM (rotations per mile) between the two tires. Then divide the 21. 5 by the RPM of your original tire,

21. 5/638. 1 = . 0337 or around 3. 5%. Not much of a difference. An indicated 60 would actually be 62. Another way to look at it, and indicated 10,000 miles is actually 10350. All in all, not something I'd worry about. JOIBO! Another way to do this is to note the mile marker on the eway, note your odometer reading, then 10 miles later note your reading. Do the calculations based on the error shown.

 

[DF5152]

try this

 

[smithinc]

Originally posted by fencebuilders

Stockers were 265's. Thanks.

why are my stock tires 245's



they are 265's i dont know what i was thinking. i believe the 17 inch rim and R70 instead of R75 messed me up.

 

[fencebuilders]

Thanks for the links/help fellas.

 

[fencebuilders]

Originally posted by smithinc

why are my stock tires 245's

Are you 2wd?