I have an 08 FX4 with the factory 18in wheels. Can I go to a 17 in wheel? The ones i'm looking at are 17x9, 5.980 in backspacing and a +25.00mm offset. Will they clear the brakes and what does all the offset, backspacing stuff mean? What will the sit like?

 

those will fit. the rims you speak of would stick out 1" more than your stockers.

backspacing is the distance from hub face to the edge of the rim. if you took the rim, flipped it over so you are looking at the wrong side of it, took a ruler and put in on the hub area and measured to the outside of the rim, that would be your backspace. now offset and backspace go hand in hand. offset is measured from the center of the rim, imagine a fake line cutting the wheel in half, that would be 0 offset. now + offset means the face of the rim is closer to you, - offset means pushed further away, you would have a big lip on a - offset rim. now you can't get a +30 offest with a 4.5" backspacing, just not possible unless you are making them custom.