The spring creates 25% greater contact pressure on the discs and is therefore particularly suitable for tuned engines. We have many other articles related to clutches in our shop. S&S diaphragm clutch spring for Harley Davidson We offer a diaphragm clutch spring of very high quality for the following Harley-Davidson models: 98-17 Twin Cam Big Twin (except 14-17 models with A&S clutch; 2017 M8) The spring creates 25% greater contact pressure on the discs and is therefore particularly suitable for tuned engines.