2003 Ford Explorer tire size

It could. It is more important to have same sized tires on a 4 wheel drive than on a 2 wheel drive. If you are in 4x4 you need the wheels to be turning at the same speed as to not be causing damage to any drivetrain components. A 245/75 and a 255/70 series tire are pretty close in outside diameter but I would replace two of them. A larger outside diameter tire will be spinning at a slower rpm than the smaller diameter tire to travel the same distance.