Originally Posted by SydneyRoo
I've checked it out, the rotations ratio is negligibly close. Factory 18s are 235/45/18 and my winters are 205/55/16
According to here:
There would be about a 6% increase with the smaller tires.
In other words if you traveled 100 miles your odometer would actually show 106 miles.
It actually says 5.833%, which @ 30mpg would show as a 1.7mpg increase.
That is just what that site says, I do not actually know how to do any of the tire size calculations.