Clutch pressure rating and spring pressures

Transmission to Rear-end

Moderator: Team

Post Reply
BirdMan
Expert
Expert
Posts: 584
Joined: Mon Jan 19, 2009 11:19 am
Location: Topeka, KS

Clutch pressure rating and spring pressures

Post by BirdMan » Fri Jun 17, 2016 9:31 pm

I have several old used drag racing pressure plates. Some with less than stock pressures. I have disassembled them all and will check all springs on tester.

I tested two sets and 1.700 appears to be close to installed height using a .315 disc. I get 190# on the red springs and 165# on the yellow springs which is supposed to have 2100/2200 pressure but multiply 165 x 9 springs = 1485# not the 245 x 9 = 2200#??

I am assuming multiplying each spring pressure times the total quantity to get the rated pp advertised rating and if not can someone who builds them enlighten me. Some did have different thickness of fiber washers in them, but same in all one pp. A couple had different thickness and or 6 shimmed and 3 not.

I am going to measure the springs at different installed heights after measuring the shims themselves to get the ranges, like .050,/.060, .090/.100 etc.
Dale C.

joe 90
Guru
Guru
Posts: 1990
Joined: Tue May 27, 2014 4:02 am
Location: The land of the long white cloud

Re: Clutch pressure rating and spring pressures

Post by joe 90 » Fri Jun 17, 2016 10:58 pm

You're confused.
Springs have a load which will be lbs or newtons.
The load changes with the length.......spring rate.
Pressure is usually in PSI which means you need to factor in an area.

It's one of those easy things which nearly everyone gets wrong pretty much all the time.


But anyway, adding them all up should work.
Springs go soft over time which means the spring rate changes.
Shimming them adds preload, doesn't change the rate.

BirdMan
Expert
Expert
Posts: 584
Joined: Mon Jan 19, 2009 11:19 am
Location: Topeka, KS

Re: Clutch pressure rating and spring pressures

Post by BirdMan » Sun Jun 19, 2016 10:17 am

I check one spring from seven different pressure plates @.030, .060, .090, .120, .150 etc shorter than the my base height of 1.700.

Color 1.70 1.67 1.64 1.61 1.58 1.55 1.52 1.49 1.46

Red 175 200 210 220 235 245 260 270 280

yellow 175 190 200 215 225 240 250 265 275

Clear 240 250 260 270 280 290 300 310 325
Dale C.

Post Reply