Diaphragm vs. Borg and Beck.............

yellow rose said
Typically, it's a bit longer than that.

But like everything else, you try and simplify it beyond what is reasonable. If you think big base pressures (I consider that to be over 1200 pounds for the applications WE are discussing) and slipping the clutch is good, welcome to 1975.

I have used as low as 600 pounds of base and 300 pounds of counter (which was just the fingers) and the clutch was locked up. At the time, I shifted at 8500 and two stepped it at 6300 (depending on conditions).

So why in the f£€k would I want to use 2400 pounds of base and just make it slip? Why not use a disc with a high coefficient of friction and make science work for you instead of brute strength?

It ain't that hard. Until you come along and screw it up with your hillbilly antics.

Not sure what size clutch you have, but my calculator says a typical single 10.375" od x 6.550" id segmented iron disc with 900 lbs total clamp is only good for around 260 ft/lbs cold.

2400 lbs of base on a typical segmented iron disc holds about 700 ft/lbs. If you dump that clutch and the tires stick, that clutch will draw whatever torque the engine is making plus whatever is available from the rotating assy until that 700 ft/lb slip threshold is met. That is unless you break something first. This is the 1975 result. I'm very familiar with how we did things back then, in 1975 I was buying Hapco clutches from my local E/MP national record holder for my tunnel rammed 301 powered '65 Chevelle, my high school ride. 4.88 gears and Mcreary circle track slicks that i had to air up every morning before school, if i washed the tires with soapy water the sidewalls would foam. Every friday was open headers day back then. Learned a lot when i bolted an aluminum flywheel on that car.

Fast forward to now, we have found better ways to make things come together more smoothly. Temporarily limiting clamp to say 2000 lbs instead of 2400 effectively limits torque that the input shaft sees to about 575 ft/lbs during those first few moments when you are most likely to break things. No longer need the monster heavy parts to hold the same power. Low base + centrifugal = 2000 lbs gets you the same slip threshold as high base - temporary reduction = 2000 lbs. At that point the clutch sees no difference clamp pressure or wear. The difference is that your method gains clamp as the engine gains rpm, my method gains clamp at a hydraulically timed rate.

My personal street/strip car currently has a 2800lb diaphragm with a 10.4" solid hub full face iron disc. It NEEDS that much clamp to hold 800ft/lbs for those times when the little 355 has both kits turned on. When i was at 700whp I used to use a 900 series segmented iron disc and that typically lasted 2-3 years with about .5 to .7 seconds of WOT slip. But here's the thing- the car gets faster the longer i let the clutch slip. For me personally, dialing in 1 second of slip is a good compromise that puts me in the comfortable position of a clutch disc lasting a full season without needing maintenance.