evodude32

iTrader: (1)

***UPDATED with results on page 6!!***



Hey guys, most of you that own the QM twin disc clutch unit knows that these things are hard to get anything over 10-15k miles out of them. One thing I did noticed after my started to slip on me is when pulling the clutch out that the disc don't really look very worn, still lots of pad thickness left on the disc.

So I took a new set of disc and started to think, would if we "could" get 10k more miles out of these?
I have a theory as in why we can only get 10k miles out of these, even though the disc look fine for the most part.
As most of you know these clutches have raised hubs. one hub being taller then the other. Have you ever tried to put the higher hub to the flywheel side and realized the hub was making contact with the other disc hub? Making the disc to not make full contact with the floater plate due to this. So obviously the disc with the lower hub goes towards the flywheel side and the disc with the higher raised hub goes towards the pressure plate.

Now when you look at the clutch hubs when you have the clutch put together, it sure seems the 2 hubs are fairly close together, but are not making contact.
This is where my theory began, as in why these clutches do not last long enough. After time obviously the disc pads are going to wear down, bringing the hubs closer together. Once you get to the point of these 2 hubs contacting each other, the clutch will start to slip since it's not making a good enough contact with the floater plate by this time due to the hubs contacting each other ever so slightly.

Now ideally it would be nice if you could just flip the flywheel side disc around, but you cannot as the splines will not reach the inputshaft of the transmission due to the raised hub design.

Here are 2 photos I chopped to explain what I am talking about, the 1st pic is of them new.



2nd photo would show after the pads on the disc are worn, causing the 2 hubs to make contact and will not seat against the floater plate properly.



I'm going to experiment with the flywheel side disc/hub. We have a lathe over here and I plan on shaving maybe ten thou off of the hub and see what happens. If this does fix the issue, maybe we can get QM to redesign there flywheel side disc/hub so it's not so raised up so high.
Is my Theory flawed here? Or would anyone agree with this theory?
I dunno about you guys, but I've seen the pads on a exedy twin disc and they are extremely thin but can get above 20k miles out of them with no issues, mainly cause it does not have the raised hub contacting the other hub problem as the QM clutch does.

20gmr

iTrader: (7)

good point. let us know how your testing goes. I'm sure this could be useful info for QM owners.

evodude32

iTrader: (1)

edit..

evodude32

iTrader: (1)

I am now 98% positive about my theory after taking some simple measurements tonight.

1st off, here is the condition of the 2 disc that came out of the car, this clutch was slipping at 10k miles. Doesn't look bad at all, infact it looks like it has plenty of life to both disc!



Another view of the disc thickness


Disc 1 measured out to 0.237"


Disc 2 measured out to 0.239"



Now onto the good stuff...

1st I put the 2 disc together without the floater plate to make sure both hubs were contacting each other and measured between the 2 disc, I came up with 0.169"
Pic of the 2 disc being measured without the floater in between them.




Next I measured the thickness of the floater plate all by itself, I came up with 0.173"

pic of the floater plate being measured



Now I took the 2 measurements and subtracted them, I came up with 0.004"
So the hubs have 0.004" breathing room before making contact.

To give you an idea of how thick 0.004" is, that is 2 pieces of paper! Not much huh?


Now ponder this for a second, all these measurements are without the clutch cover all sandwitched together. These measurements were all unloaded, no pressure under the disc/floater plate.

Now put the clutch together, tq the clutch cover bolts down and it will squish everything together. I'm sure it will squish ATLEAST 0.004" or more under a loaded clutch cover since the clutch cover is what? 1600lb pressure plate? or more? Thus making the 2 hubs contact each other ever so slightly, causing the clutch to slip as it does not have and will not have a proper seat against the floater plate. When this happens, it's hard for the pressure plate to seat both disc, even to the flywheel since the one disc is not making 100% contact with the floater, hence will not apply pressure to the next disc then to the flywheel.

SO I think I have proved why these clutches only last for so long, it's not a disc issue, it's a hub to hub contact issue.
I will be shaving atleast 0.010" off of the hub and reassemble the clutch to confirm my theory. I should be able to get all this done by the weekend and see if the clutch still slips. I'll keep everyone posted of my findings.

evodude32

iTrader: (1)

After thinking about this, I think I'm going to take a bit more off the hub, more along the lines of 0.045"-0.055" This should give it plenty of breathing room for the disc to wear down to atleast 0.034"
Once the pads on the disc reaches this thickness then the hubs should make contact again, but this time will be some what of a warning to let me know the disc are done completely but not metal on metal. The disc PAD thickness currently on these disc are at 0.089" (one side of the disc/pad) total both sides of the pads (one disc) are at 0.179" (not including the metal surface the pads are on, that would come out to 0.239")

blackgsx01

iTrader: (17)

Please keep this updated! I would love to buy this clutch and modify it new like this and be able to get 20k out of it.

keeler

iTrader: (3)

I'll give you props for trying. Hopefully it works

CMB

iTrader: (5)

I understand your theory..I wonder if the engineers at QM know this and just produce them that way so we can buy rebuild kits? Maybe its not so much the thickness as to what happens to the disk material and floaters when it hazes? Should be interesting, thanks for the effort!

04WWRS

iTrader: (18)

Have you adjusted it at all after it started to slip? I'm not sure of the peoceedure but I know they are supposed to be adjusted after awhile.

APM Racing

iTrader: (4)

Interesting theory. I'll contact them (QM) today and see what they think. I know the disc start out at .250 thick and somewhere around .230-.235 start to slip. They claim right around .030 total wear is where the clutch loses it grip. So i am not sure if i would take off that much material on the hub. Maybe take off the .015 you lost and see what happens?

sabastian458

iTrader: (25)

I would take the full .045-.055 but split it between both hubs.

boostedtres

iTrader: (4)

subscribed....very interesting theory. props to you for trying something new. hopefully it all works out and either you get more life outta it or QM changes the desgin! gl brotha

feautoevo

iTrader: (8)

Bump... I just ordered this clutch... any updates yet... lol

Good writeup!

WHTEVO

iTrader: (18)

I would be careful when taking more material off of those hubs. I think QM made them thicker for a reason. On the DSM units, the hubs are thinner and not as beefy, but they also have issues with the hub area cracking. Definitely keep us updated though. I am interested since i have a QM in my Evo as well. Good luck.

Aaron

PATRICK B.

iTrader: (5)

Sub'd for results i don't DD my Evo w/ the QM so i don't worry too much about longevity but would liek to see what you come up with!