There are two major factors to going fast: torque and traction. But getting the torque from the engine to the tires warrants some attention. If you're of the stick-shift persuasion, you've got your work cut out for you selecting the right clutch-too much clutch and you've got an unmanageable bear on the street, not enough clutch and you'll be singing the blues on the side of the road. High-powered street cars with a lot of torque are in a no-man's land of sorts. Many of the aftermarket offerings are just too soft to hold up against the onslaught of twist coming off the flywheel. Since our theme this month is managing torque in high-powered street cars, we wanted to take a look at those limited clutch offerings that fit the bill of a max-effort street piece. We'll look at the important considerations of selecting the right clutch, and the materials you have to choose from. Finally, we'll get into some hard-core recommendations that just might fit the bill for you.
To dig deeper, let's look at what problems can occur if the improper clutch is chosen. Most complaints about heavy-duty, sometimes overkill clutches are about chatter and heavy pedal pressure.
Chatter Chatter occurs when two hard surfaces touch each other, and a vibration is started. The clutch is not the only thing responsible for this feeling, though it is a major contributor. Worn U-joints, incorrect pinion angle, a bad finish on the flywheel or pressure plate, loose motor mounts, a worn pilot bushing, or any loose drivetrain or suspension components can exacerbate what may have started out as a chatter too minor to have noticed on its own. The best thing to do first is to fix all the non-clutch variables. The nature of the harder, longer lasting, grippier materials that are best at managing high torque loads is that they are more prone to chatter. The way the top clutch manufacturers combat this problem is to employ what is called the Marcel. A Marcel is a crimped plate between the two layers of friction material that acts as a spring to cushion the engagement and disengagement of the clutch. This is the only thing a manufacturer or rebuilder can do to the clutch disc to relieve chatter without changing the composition of the friction material.
Heavy Pedal The grip of a clutch can be figured by a simple formula. Surface area, plus spring pressure, plus friction material, equals desired holding power. Any of the three variables can be changed, as long as they are compensated for someplace else. The old-school, four-speed drag cars of the 1960s and 1970s increased their holding power by increasing the spring pressure, resulting in a heavy pedal. Today's technology with better materials and larger discs allows the spring pressure to be decreased for easier operation.