I would like to put 315's on on my 07 H3, my dealer says they can reprogram only up to 285's...has anyone dealt with this issue? its a lease so I dont want to go over miles.

 

if you put bigger tires on, then the mileage will be lower than actual miles... not by much, but over a period of a couple of years it may add up a bit.

Larger tires = more distance covered with fewer rotations of wheel. Think of it as "Bonus Mileage" lol You MPH will be lower than "actual" as well.

It will cause less MPG, but again, your mileage wont be correct, therefore causes lower mpg too.. (im sure the added weight causes a little, but not enough to calculate)