There has been a lot of confusion for tire size limitations in the State of Maine for several years now. The general thing I have heard is that “you are allowed to go up or down two sizes.” But, does that mean inches, p-metric sizes, martian tire size units?
I’m interested in running some non-stock size tires on my truck, so I emailed the Maine Bureau of Motor Vehicles to get a good answer. As it turns out, that isn’t the exact law. You are allowed +/- 2″ in diameter from the stock tire height (whatever is in your door frame) regardless of if you have ABS or not. If you do have ABS, any change in tire diameter will require your computer to be adjusted to be legal. Regardless of size, it is against Maine law to put on a tire that does not meet or exceed the speed and load rating of the tire that came on the vehicle out of the factory.
For posterity, here is the exact message I got back:
Good morning Mr. Raymond,
The tire size you would like to go to is legal. Two tires sizes larger
or smaller is defined as not more than a 2″ change in overall tire
diameter. Since the two tire sizes are equal to the same height the
215/85/16 is fine as long as the load range meets or exceeds the
manufacturers recommendations. If the tire size were a different
height, but within 2″ and the vehicle was equipped with ABS then the
computer would have to be reprogrammed or replaced so that it is
synchronized to the new tire size. Since the tire you want to got to is
the same height there is no need to have your computer modified.
Have a great day!
Lt. Brian P. Scott
Maine State Police