Is this how to measure break away torque?

[Zmanco]

Now that I've got some miles on the new R180 PowerBrute, I was curious to measure the breakaway torque. Here's how I did it:

 

- Jacked up just the driver side leaving the passenger side on the ground.

- Using a beam-type torque wrench, I put a 13/16" socket on it and put it on one of the lug nuts. I aligned it so the line of the torque wrench goes through the center of the wheel.

- I gradually increased pressure on the wrench until the wheel turned smoothly and took the reading.

- The length of the torque wrench from center of the socket to the tip of the beam where I read the value is 12.5". The distance from the center of the wheel to the center of the lug nut is 2.5".

 

I am assuming that my total lever arm is 12.5 + 2.5 = 15". Hence my readings need to be scaled by 15/12 = 1.2.

 

My readings were all between 48 and 50 lb-ft. So if I've done this correctly, the breakaway torque is ~60 lb-ft.

 

Is this a proper way to measure it? And does that value seem ok?

[jt1]

The length of the torque wrench from center of the socket to the tip of the beam where I read the value is 12.5".

 

Don't use the distance to the scale, use the distance from the socket c/l to the center of your hand where you are applying pressure to the wrench. Otherwise your method is good.

 

I don't know if that's about right or not, maybe some other PB users will chime in.

 

John

[bjhines]

that sounds like a pretty good approximation for breakaway torque...

 

Keep in mind that the low(60*) ramp angles make these competition units lock up tighter under power.... typically they do not need to be shimmed to have 100+lbs of breakaway torque like the cheezy factory 300ZX units...

[JMortensen]

http://www.gordon-glasgow.org/lsd4.asp

 

That's the correct procedure. Without taking it out of the car I think you'd need to at least drive it around between each test to get oil on the clutches. John is right, what you've got should be fine and the more aggressive ramps should make it act like a more tightly shimmed cheesy one even without the high breakaway torque.