Originally Posted By weedburner
Here's some very general calculated torque capacities per 1000lbs of clamp pressure for typical "10.5" clutch discs (actually around 10.375" dia od friction material)...

organic- 180ftlbs
dual friction- 276ftlbs
ceramic- 293ftlbs
iron- 289ftlbs

From those numbers if a 440 made 600ftlbs, here's the minimum amount of clamp required to hold the torque for various friction materials...

organic- 3334 lbs
dual friction- 2175 lbs
ceramic- 2048 lbs
iron- 2076 lbs

With the typical adjustable you are trying to slip as much as you can off the line without slipping too much in high gear. An organic disc is going to limit what you can do as it loses cof as it gains temperature. Ceramic is a pretty much the same compound as a ceramic brake pad, heat doesn't really change cof much. Iron does exactly what you want as it gains cof as you work thru the gears, which widens your tuning window.

From the above you can also see why ceramic has such a bad reputation for being like an "off/on switch". They are typically paired with a pressure plate suited to hold an organic disc, when they should be paired with a pressure more like that for an iron disc.



ok, so if I would do all clutch slipping with the pedal the "ideal" clutch setup would be a pressure plate that has just enough base pressure to not slip at idle and added counterweight pressure that follows the torque curve throughout the rpm range.
Well, since the added counterweight pressure usually can't follow the torque curve perfectly (centrifugal pressure increases exponentially whereas the torque curve usually has more of a logarithmic shape) you start with a higher base pressure and add less centrifugal pressure, correct?

In my case I have a McLeod B&B/Long PP (360951) with 2400lbs base pressure and counterweights. If I would use an organic disc I need roughly 1000 lbs of centrifugal pressure at the rpm I hit 600 ft/lbs of torque (let's say at 4000rpm) for the clutch not to slip (2400 base + 1000 = 3400 pressure). At 6000rpm the centrifugal pressure is more than double that at 4000rpm which is not really necessary as the torque increase between both points is only a few ft/lbs.
Would I be better off if I lower the base pressure and centrifugal assist (less or no counterweights) and run a disc with a higher friction coefficient than an organic disc?

This only takes into account going through the rpm range without shifting (where you don't want your clutch to slip).
When shifting you want some slippage though - otherwise shifts are too violent (at least for a street car). So is a dual friction disc the solution in a street car? It would have some slippage when shifting but a much higher cof (less base and centrifugal pressure needed).