This SES Suspension Upgrade replaces the jounce stop on the frame. Its unique design ensures superb ride quality – loaded or unloaded. (There should be a ½” to 1 ½” gap between rubber spring and frame to ensure unloaded ride quality.) Unlike other auxiliary spring systems, the SES Suspension Upgrade guarantees the best of both worlds.Timbren Suspension Kits (SES Kits) are designed to enhance the suspension of your vehicle. Easiest to use: Rubber cushions absorb road shocks and automatically adjust to uneven loads or road conditions. Easiest to maintain: There are no airlines or fittings to allow leaks. Simply bolt the kit on and you are set for a lifetime of trouble free suspension. Easiest to install: There are no holes to drill, no airlines to route and SES Kits can be installed in a matter of minutes using basic hand tools. The softer ride quality of todays trucks and the mediocre suspensions found on most trailers can cause excessive trailer sway, instability and suspension settling. Timbrens high performance suspension packages will ensure added safety and peace of mind.