[eschaider]

Ernie,

You're right about the owner's driving style. The best parts can be broken by a determined individual. That's not what we are looking to emulate or evaluate.

The caveats for friction clutches apply equally to both single disc or n-disc clutches. Abuse the unit and you shorten its life. Abuse it a lot and you shorten it a lot.

The clutch manufacturers came out with streetable twins twenty maybe thirty years ago. I believe McLeod was the first but I am not absolutley certain about that. I do know that there are multiple manufacturers that have offered these units for at least ten years, some manufacturers more.

The big benefits are additional friction area, reduced plate loads (softer pedal), silky smooth engagement, and substantial torque capacity reserve. They simply remove the bad manners and reduced service life of the high capacity single disc equivalents.

If you put serious power through the clutch in a drag race environment then you need sintered iron components, floaters that center on clutch stands and are not secured by straps along with a borg & beck or better a long style cover for the more secure locating of the pressure plate. You will benefit from the tunability and adjustability of plate load through in can finger height and adjustable static pressure on these units. These are brutes but they are not street units and should not be compared to them. One is a severe duty race clutch the other a high capacity street clutch.

I think release mechanisms tend to be a preference election of the individual builder and could essentially be anything you choose. Moreover a release mechanism failure is a different animal than a clutch friction component failure. Although a release mechanism failure could induce the other. Release mechanism induced failures tend to fall into the same category as operator misuse induced failures. As you pointed out in your own case the single disc failure was most probably not a shortcoming of the unit but rather an unintentional (I presume) misuse/operation by the driver.

You are absolutely correct about the number of single disc units in service vs the number of twins. I suggested that for evaluation purposes "... All it takes is simple four function add, subtract, multiply and divide skills. In fact you can be average in three of the four skills as long as you can add." However not withstanding the evaluator's ability to be average in three of the four skills, unstated he would still have to be able to divide otherwise you can't determine the failure percentages. Of course a fall back would be a four function calculator and let the machine do the work.

Data collection would probably involve some type of a thread including a poll and suprise suprise we get numbers that not only tell us how many type info but also problem type info. Of course this would only be interesting if the individual wanted to know. If he wanted to complain or perhaps make untoward remarks about products or manufacturers then this approach would yeild less than desireable results.

I think we have enough folks who have replaced one or more clutches and spent good money in the process, that this type of information represents real value to them. It deserves to be made available without potentially misleading remarks that would otherwise obfuscate the real world.

Most people below 550/600 HP don't have the same types of clutch service issues those above 600HP do. When you hit the 600 level a lot of things begin to behave differently especially in terms of wear. The thread's title "Beware of dual disc clutches" along with the poster's admitted non use of the product speaks volumes about the message. Interestingly, although I am sure somebody has, I didn't turn up any posts of dual disc users complaining about those stated "problems".

We should be expolring ways to make things better for each other not clouding up an already demanding variety of choices and decisions to improve our cars and pieces.

Ed