Calculating MPG and Odometer with bigger tires

[TimHerald]

How do I do this ? I have 35” tires (285/75/r18) that replaced factory Michelin 265’s.

I read somewhere that my speedometer is basically off 2 mph at 80, but how do a calculate mpg and miles driven on odometer ?

 

[jay3253]

Test thr speed vs gps speed reading. Mine is now correct going from stock (to slow) to 33.5in tires. Once you have the gps vs meter speed difference the percentage change there should be the same percentage change in mpg. It will get you close enough anyway.

 

[COSmurf]

How do I do this ? I have 35” tires (285/75/r18) that replaced factory Michelin 265’s.

I read somewhere that my speedometer is basically off 2 mph at 80, but how do a calculate mpg and miles driven on odometer ?

Use this: Tire Size Calculator - Compare Tire Sizes | Tacoma World to find the speedometer difference given your new tires. It will give you the speedometer correction factor (1 + error percentage). For mine, I am understating distance, speed and MPGs now by 3.3% given my increased tire size so I can get the computer readout and adjust by multiplying by a factor of 1.033 to give the accurate reading. Hope that helps.

*In your case, if you went from 265 70 R18 to 285 75 R18, your readouts are probably understating your distance traveled, speed and MPGs by 6.4%. So you should be multiplying your readings by 1.064 to know what the actual readings are.

 

[TimHerald]

Thanks guys. The difference in speed accumulates the faster you go but this gives me a much better idea on mph and mpg.

What about distance traveled on odometer?