Changing tire size

[Viberrrr]

The question was just asked in another posting how easy is it to change out the overdrive. I'm assuming to improve mpg. My question is would changing to a different tire size change the gear ratios enough to effect the gas mileage? I don't care that it would effect the speedometer if it improved things by 1 to 2mpg

[djb383]

The Vibe 1.8L is not exactly a torque monster, so going to a larger diameter tire just puts that much more load on the the engine and drivetrain. The factory has already figured out the best overall diameter for performance and economy. My $0.02.