Coil springs are the most common used spring in most all motor-sports today. The reason is because it is very easy to change the component as well as check the rate, unlike leaf springs and some total hydraulic shock suspensions. Furthermore, with the incorporation of the coil-over spring/shock type suspension, the coil spring and shock ratio is close together and operates as one unit. Of the many components that can be changed on a race car chassis, the coil spring change brings about one of the most adverse effects on a chassis.
Simply put it, buying GOLD COILS may save most any race team money. By purchasing springs that are already accurately rated, you will not have to pay your engineer ($$$$), team manager ($$$$), or crew chief ($$$$) to rate springs that you have purchased. Furthermore, a race team will not have to purchase additional springs to fill the void left by the springs that did not rate properly to the theoretical rate that they where suppose to be. In addition, teams would not have to purchase expensive testing equipment. Moreover, accurate spring changes will allow teams to be more progressive in their test sessions and eventually reflect in their qualifying efforts and then onto the race.