...to clear my 255/60/15's that don't fit under the fenders. I am using air shocks to gain about 2" of height(60 to 70 lbs pressure). This is working fine but, I don't think this is the best way. I installed those bolt on "spring boosters" this weekend. They gave me about 1/2" and some stiffness, which I do not mind. The stiffer it is, the less I have to raise up the rear.