High gear clutch slippage

[Mark Madison]

Originally Posted by Jeff Lee

Besides the mechanical issue of changing gears due to ratio, the clutch will slip more or less dependent upon the time spent between gears. A racer that uses the clutch to shift, no matter how blindingly fast he may think he is, requires a completely different clutch tune that a racer that does not use a clutch to shift. On top of that, the transmission (clutch or clutch assisted by design) choice affects slippage even if the clutch is not used to shift gears.
All of these issues can be tuned with the proper clutch. That includes not only the basics like base pressure and counterweight, but also lever design and friction materials used. The Sportsman Single 10" I have used in the past and the Sportsman Dual 7" I am going to use in the very near future has heat shields made from specific alloys not found on competitors components. The clutch disks employed on these, while not a trade secrete by design (like the heat shields), are specific to the application by material and density.
Finally, a racer that has had his clutch friction materials "rebuilt" by resurfacing instead of having friction materials replaced with new components will not see the same results by rebuilding vs. replacement parts. The reason is rebuilding by cutting surfaces lessens the thickness of the materials and their ability to absorb heat and as a result the clutches friction materials service life can be severely shortened. The thinner the parts, the quicker they will warp. The quicker they warp, the quicker you reduce the plate loads to unacceptable levels. This causes the racer to run excessive base and / or counterweight in an attempt to overcome the slippage. In the end, this is just a band-aide and performance (and more importantly; consistency) is impacted greatly.
So Stewart, there are many factors to consider. Hope this helps.

So replacement of heat sheilds is normal with a $900.00 clutch rebuild. mark Madison