I have a 4" Superlift with lifted rear springs and they highly recommend extened brake lines. When the shop had the lift on and standard brake lines they were stretched tight as guitar string when the suspension was fully extended. It looked like the line was kinked to the point of snapping. Since my lines were 18year old I figured it was a cheap investment considering what that they are resposnible for. With the extended lines from Rough Country (nice quality) I not only have fresh new lines I have peace of mind as well. Get new extened brake lines period.