Both! SumoSprings are used for too many applications and benefits to list. Because of their progressive spring rate, and cushion like urethane material, SumoSprings absolutely increase ride comfort. SumoSprings are also springs! Meaning, they will help carry loads. Without SumoSprings, your original equipment carries 100% of the load. SumoSprings work in conjunction with your original equipment to share the load, helping level out sag and reduce wear and tear on your original equipment.