Originally Posted by special tool

Yes - I use something similar to the 6 puc solid hub on that site.
But mine is copper/ceramic.

Jimbo1111 has found a disk tthat is BRONZE/CERAMIC. Thee bronze material is supposed to ease the engagement just slightly, yet retain the awesome friction (and heat management!!!!!!!!!!!) of the copper/ceramic.
If I was buying one now for a 951, I would probably get the one that Jimbo111 got.
I don't know where the hell he got it, however.
Send him a pm - hopefully he'll be in a good mood.....

Originally Posted by Charlie944

I did a some more research and found an article in Turbo Magazine on clutches: Kevlar, for instance, is known for its insulating properties. As a friction material, this is a problem. Kevlar doesn't recover from overheating very fast because it doesn't transfer the heat off of the surface. The result is a material that can cook the mating surfaces (flywheel and pressure plate) and has a lower-than-stock coefficient of friction to boot. Yes, it lasts a long time if treated right, but it's not ideal.

Contradictory to the above I found this: http://www.southbendclutch.com/kevlar.html

I will have to find the friction coefficients of carbon type clutches and the Kevlar.
The formula for torque capacity is:

T = P x F x N x R
where:
T = torque in ft-lbs
P = pounds of clamping force
F = coefficient of friction
N = number of surfaces (generally 2)
R = radius of gyration (mean radius of the friction surface) in feet