As previously mentioned it does both. I went from having saggy OEM springs with about 600 some odd pounds of weight in the rear end to having z71 springs with the same weight in the rear. I also installed OEM length/spec bilstein shocks in the rear when I upgraded the springs. I am far from bottoming out the rear end with the lift because of all that extra weight that is constantly in the rear. It does ride harder when I hit road bumps with the z71 springs but my OEM springs and shocks were totally shot. So bad that I could compress the shocks with my hand. It to me isn't that bad of a ride with z71 but you should look into getting different shocks if you aren't loading down the rear end with weight all the time as you can cause the shocks to bottom out on extension. I have never had that issue with the amount of weight in the rear from my system, even doing 40mph over an intersection by my house that has a huge bump in the road will not make it come close to bottoming out.