That's interesting. I have never seen pressure plate loads in service manuals. There are different methods of measuring clamp load so you have to compare apples with apples.

The method we use measures peak load going both directions (compression and rebound) which actually measures load plus friction in one direction then load minus friction in the other direction. We average the two numbers so that friction cancels out and all you have left is true clamp load.

Some aftermarket clutch companies will measure only at the new installed position which only matters when the clutch is new. They might place their performance clutch directly on peak clamp load and then it wears goes down from that point forward. Compared the stock which actually gets stronger with wear first then falls off they might claim a 30% increase when really it's about 15% when you compare peak clamp load. The kicker is that the clutch doesn't last as long either.

Some companies claim all kinds of numbers but actaully don't do any clamp load measuring. These are really entertaining when you know what they actually produce. So there is a lot more to it than what one might think when it comes to clamp load.

To get away from measured clamp loads, we always publish a percentage of increase and estimated peak torque capacities. We also provide the math formula we use to calculate torque capacity right in our catalog.

 

Regardless of the gearing or launch rpm, the clutch torque capacity doesn't change, except when the clutch is actually hot. What happens is the resin that holds the friction material together which is lapped in (glazed) starts to melt. Not only doesn't this create a terrible smell but it also rapidly takes a layer of material off the disc. Once it cools it will actually hold more power until you break it in (glaze) again. It will also keep wearing rapidly until you do glaze it again. The other problem with overheated clutches is that the surfaces warp and you don't get full contact. If overheating is the issue, then it will be a major problem to contend with.

Materials: The material on the EVO disc is really good stuff and there is a lot of it compared to some cars. I cannot think of a good improvement in an organic material since you are basically at the mercy of the resin's melting point. Our performance organic might help a little but both materials have worked well for John Shepherd in his 9 sec. DSM and his clutch is much smaller.
Kevlar will wear slower but will hold less power and will heat the opposing surfaces prematurely since it doesn't conduct heat away from the surface.
A metallic will be too harsh for street IMO but may conduct a little more heat, depending on surface area.
A multidisc metallic will have even more trouble with warpage, wear, etc. if heat tolerance while slipped is the real issue. This is why you don't see race cars (Nascar, IRL, others) slip the clutch. It is better to just break the tires loose. On the EVO you don't have that luxury.
Carbon/carbon is more heat tolerant, but hell on the wallet and not really meant for the street.

From what I know so far, I think the EVO clutch failures are not from one single problem. We will see.

 

I was suprised myself to find this number in the specs. Only thing I figure is maybe they have a procedure for checking the pressure at the clutch fork, where the slave cylinder pushes. I will look again and see if they have a procedure on checking this on the car or off, or if it was just FYI data.

There was a noticeable difference in feel once I adjusted the free play of the clutch, the pedal was a good 10mm lower then it should have been and therefore the travel distance was not within spec. Interesting to see if anyone else checks theirs to see if the are all like this. I could clearly see the pushrod was well threaded into the u-bracket that attaches to the pedal. It automatically seemed like it was in to far just looking at it.

After a good drive, I did crack the bleeder to check for pressure and only got normal flow, so the the master cylinder is reseating properly and not holding pressure in the line.

 

Hi all,
My EVO is in the shop now because the throwout bearing was bad. After mitsu pulled everything apart they decided that they needed to replace not only the throwout bearing but also the flywheel, and pressure plate(all defective from factory). I went ahead and replaced the clutch disk($111.00) myself to save labor costs later on. It was pretty worn already.
I now have 13,000mi on my EVO.

 

Ah HA!!!!

Is this the culprit in most??

 

So what symptoms would a bad throwout bearing show?

 

Noisy?? Weak engagement??
ACT MAN??

 

Dirk Starksen of ACT Inc seems to be the knowledgeable resource here. I don't know about everyone else but the rumors and hear say are getting real old. Let's see what ACT comes up with and go from there. I believe Mr. Starken knows more about clutches than anyone else here.

 

Noise that changes (gets better or worse) by slightly depressing the pedal. When it gets really bad sometimes you will get a vibrating pedal you can feel in your foot.

 

Of course ACT knows more aboutthe clutches then anyone else here. Everyone is just asking questions and discussing the topic, after all this is a forum. I don't know that it's rumors and here say. For the most part people are relaying thier experiences with the clutch to ACT to try and give them information from the users perspective, since they don't get to see all these cars directly.

 

Spoken by a true newbie..

Duh..


Spoken by a moderator and someone obviously READING thses posts before jumping aboard and commenting............NEWBIE!

 

Thats funny (sarcasim) because when I showed my regional rep that applying a slight bit of pressure to the clutchpedal while the car was making the decelnosie that the noise went away (testing to see if the noise was clutch/throwout bearing) he said it was becuase I was applying just enough pressure to unload the drive line and that was preventing the back faces of the gears from "being excited." BTW that is what mitsu contends the decel noise is, the back faces of the gears. Not saying that isn't part of it, but I think the audible portion of the vibration is coming fromt he clutch prings or the TOB. Anyway, don't want to get too far off topic......

Once ACT gets a setup for the evo to market I'm going to petition Mitsubishi to check my throwout bearing and clutch assembly. If they won't do it I'll take it to a certified third party and have them do it and install an ACT setup while there at it. Then If the bearing turn out to be the source of the noise and or turns out to be bad I'll petition mitsu to reimburse me for the labor. Like they ever would....

Thanks again for your involvement ACTman.

 

I have to tell you that I am going with them on this one. At least that is my internet expert evaluation since I have no clue what this noise actually sounds like. If it changes with accel or decel or coast, it has nothing to do with the TO bearing. A highly doubt if the disc is defective. The stock disc is pretty indestructable. A new one will most likely do the same thing.

The engine's natural torsional vibration is what normally causes transmission decel noises. The possible reason that the noise goes away when you push on the pedal is that friction of the thrust of on the crank reduces the amount of vibration. Torsional vibration and disc dampener design are not subjects I want to try and explain in a forum like this because it gets really complicated. I do still have other work to do.

 

Darn,

So TOB and even a new clutch may not help with the decel noise?

Oh well, maybe I'll just live with it and go ahead with a power mod, heh. Definitely want to replace the clutch anyway if it starts to give me problems.

Thanks for the info.

FB

 

I haven't noticed any odd decel noise coming from my car. I even heard a sound clip of someone having the decel noise. Guess it is the luck of the draw, lol. Maybe I just got lucky. I'll have to try to get it up on the board if anyone is interested.