Here is the 'what you need to know' information about clutches.
The engine side of this clutch system is made up of one part, the flywheel. The transmission side is made up of two parts, a pressure plate, and a friction disc, (friction disc, six puck version seen here
http://www.deucecoupe.org/img/act6puck.jpg )
The theory is that the engine spins the shaft that the flywheel is on. Now, that needs to be transferred to the transmission, but with just a shaft how can you do it? Obviously a small surface area such as a shaft isn't going to do it, thus you have a flywheel and a pressure plate. That was in the early days. The thought was that the flywheel would create a surface that the pressure plate could grab ahold of. Early testing failed, in order for the flywheel to be light enough to allow the shaft to spin, it would be too weak to stand up to the pressure from the heavy pressure plate. Eventually the friction disc came into the picture. This sits up against the flywheel and spins along with it. Disc ones look like one big round circle, and pucked ones are like the one you can see with the link above. This created a surface that the pressure plate could grab ahold of, and act as a median between it and the flywheel. Think like brakes now. Normal rotors are good but slotted or cross-drilled rotors are better, as proven by design. Clutches are the same way, the different designs are intended to allow more grip.
Next you might ask... my stock system was pretty good, what do I need more grip for? Well when you start making higher horsepower, eventually your disc system with its basic material isn't able to hold onto the flywheel when it starts spinning faster. It slips off the flywheel and you aren't able to transfer all the power your car is making to the transmission. Now you're losing power for a very lame reason. Heavier pressure plates and stronger friction discs are designed to withstand these higher power levels. It's a must for anyone reaching certain power levels.
Another question I hear alot is - Why do some people say that they had problems with a heavier plate or a different disc? Well, that's because the heavier the system, the harder it is to maintain rev's. Ever wonder why you have to rev as you're starting to move your car? Simple! When you're letting off your clutch pedal, and your pressure plate is closing in on the friction disc, when it makes contact, the heavy pressure plate slows the rotation of the friction disc down, thus, slowing your flywheel, then slowing the crank, then RPM's drop and your engine starts to die, you give it gas to maintain those RPM's and the spinning of those particularly vital parts. So with a heavier pressure plate or a stronger clutch disc, when you start to make contact it slows it down even FASTER and you have to give it more gas or at least more abruptly give it gas in order to keep your car from stalling. Thus, making it a bit harder on some heavier systems to enter into 1st gear.
This is real basic and I didn't go into all the detail I could. if you need to know anything else. Feel free to ask
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by that1mexguy » Fri Sep 30, 2005 4:50 am 
