SHOCK SPRINGS
When installing an extended swingarm on your bike, you drastically alter the leverage ratio and load on your rear shock. In order to maintain the correct suspension action, a new spring is mandatory. At Trac we have a complete selection of springs for almost all sportbikes. For street bikes, a stiffer spring is almost always necessary to compensate for the longer wheelbase of an extended arm, For the serious drag racer however, sometimes a softer spring will allow for the maximum performance. Below is spring selection chart for a Hayabusa to illustrate the rates recommended.

RE-VALVING
While a correct spring is always necessary to support the riders weight and swingarm length, it is the internal valving of a shock that is the real secret to proper suspension. Valving is what controls the rate at which the shock is allowed to compress and rebound. When you install a stiffer spring, it puts much more pressure on the shock and causes it to rebound too fast resulting in an unstable ride. For drag racing, achieving the desired results can be complicated. When a very soft spring is used, the reaction of the suspension needs to be controlled by valving. By dramatically increasing the compression damping, we are able to utilize the full travel of the shock at a functionalbe rate. Rebound damping is also a critical part of a drag racing set up, as a controlled rate of extension will keep the weight transfer to the rear of bike, providing continued traction.