I recently installed Kosei K1's, 13.5 pounds but went with 195/50/15 vs the factory 195/55/15. I'm curious as to how much my MPG readings might be off being that I'm running a smaller tire? I filled up today and had an average of 38MPG but the wheels/tires had only been on for one day.


Thanks!

 

i am wondering that myself!

 

Use a tire size calculator, which will give you the overall diameter of the wheel size you chose vs. what you should have. It will also tell you what the difference of the rolling circumference in a % which is the difference that your mpg reading is off. Use google and search tire size calculator.