I don't mind crazy transmission noise. Actually, I love it. But I've never driven a car with a solid hub on the clutch disk. I'm thinking about going with the exedy or cusco twin disk, but i'm trying to decide whether I want a sprung hub or solid hub .

So are we talking herky jerky starts or what?

 

i had a solid hub on my car, the biggest gripe was the noise, since its unsprung, you get a high pitched chip like a sticky lifter sound. at least i did. i would prefer a sprung clutch due to the fact that the springs absorb a lot of shock.

 

On 90-99 DS<, the problem with solid hub is the AWD driveline. When ever your coasting out of gear the unsprung hub is tranferings alot of vibration and so forth to the tranny. the DSM trannys tend to break seal and shim and internal parts, **** gets out of spec and they start falling apart. To much internal vibration

 

get a sprung hub clutch if at all possible.....power levels and intended usage will dictate whether or not that is possible

 

Springs in the center of the disc are designed to absorb torsional vibrations that rattle the gears and make noise. They do not make starts smoother.

An aggressive material (metallics, ceramics, etc) will tend to chatter and solid centers in these discs actually make chatter worse, not better. Chatter occurs when the engine winds up in it's mounts as the clutch is being engaged and the clutch will briefly disengage, allowing the engine to bounce back, and the clutch engages again. This all happens very fast so you get a bucking, shudder, or chatter. Without the wind up affect of the soft mounts, even the most aggressive material will take off totally smooth.

OK, now back to the clutch disc. If you put springs in the center of a disc that wants to chatter you get more wind up affect, not from the engine, but from the disc springs. Chatter is now amplified. This is one reason we do not put springs in the center of our racing puck discs. I am not saying they don't have their place. The vibrations can not only make noise, the vibrations can also wear the gears, etc and shorten transmission life. I don't think this is a matter of shock loads so power or abuse is not really the issue. The springs are not strong enough to really reduce the shock IMO. It's simply vibration that may cause the damage. I hope this info helps.

 

ACTman, what clutch do you recomend for the smoothst and long life for a EVO 8 ?

 

Silly question! ACT, of course. I think we offer a great street setup for higher powered cars. However, I am just a little bias.

Actually Kevlar may be the best if you are only looking for smoothest and longest life. Unfortunately it will not hold the power very well (lower coefficient of friction than stock) and it tends to put too much heat into the mating parts since Kevlar is such a good insulator.

So you see there are other considerations such as torque capacity, heat tolerance, pedal effort, burst strength, shifting quality, etc.

 

So when is ACT coming out with a twin disk for the Evo? I have a 2600 w/ street disk in my talon and I love it. Only reason I'm looking for a twin disk is because I don't want the high pedal pressure on my daily driver.

 

We don't have any immediate plans to make a double disc. I don't like the tradeoffs, especially for street use. I admit, I am kind of a purest so my demands are higher than most. Keep in mind that most high power production cars out there run a single disc clutch. We could always trade pedal effort for clutch life, but I don't think that is a wise choice.

 

Curse you for beating me to the sprung hubbed thing, Dirk! CUUUUURRSSE YOUUUU!!!

Not to stray off topic, but approximately how long (generally speaking) do you think it would take to see the adverse effects of driveline shock on a spring-hubbed clutch as opposed to solid assuming moderate to mildly large power increases?

 

I wish I had a simple answer. Most Honda guys run a long time on a solid disc with no transmission problems whatsoever. I have seen splines strip out on solid or springs break and pop out after only a few thousand miles. If you have a V8 either one will last for a very long time versus a four cylinder. So much of it has to do with the car's setup and where the weaknesses are. Nissan Sentras for instance, hate solid centered discs.

Factors that increase torsional vibration are less cylinders, hotter cams, higher compression and higher boost. Factors that dampen out this vibration are weight of rotating mass (crank, flywheel, dampeners), dampening devices (harmonic dampener, spring center clutch plate, or dual mass flywheel.

John Shepherd's DSM runs basically our off the shelf parts with little problems. On the other hand Brent Rau's DSM car has to have dowels between all the flywheels bolts just to keep the flywheel on. Brent's car makes some wicked torsional vibration. Even his old AWD was like that. Both John and Brent are making similar power, but they act totally different. Obviously one is potentially going to be harder on parts than the other.

 

my question...what is the difference between and advantage/disadvantage of a twin/triple plate clutch as oppsed to a single plate??

 

These are generalizations and can be disputed. Some have features that others don't. In general , here is how I see it.

Advantages to multiplate:
1. Double or triple the torque capacity if all else (clamp load, friction, diameter) remains the same.
2. Ability to reduce size, pedal load and clamp load and still achieve good torque capacity.
3. No drive straps are used typically, which mean that the clutch can take dramatic loads in both directions, not just one.
4. More surfaces to dissappate heat.
5. Lightweight for better engine response.
6. Built for racing and typically can hold great power.

Disadvantages:
1. Cost. You have to replace clutch and flywheel. The parts are not cheap.
2. Exclusive. Your have to use only their parts. If you don't like their disc, or flywheel, tough. Many switch to a push type clutch (less efficient) because of the Exedy Patent on release bearing design.
3. Noise. Gear rattle will not only occur from not having springs in the center (typical of most) but also clutch rattle will occur from the lack of drive straps.
4. Longevity. The clutch rattle is from the cover being hammered by the pressure ring and floaters which is not kind to parts. Also twice or three times as many surfaces are wearing and the working range of the pressure plate is typically much shorter than a single disc.
5. Disengagement. Typically no lift mechanism is built into the pressure plate so there is really no air gap, causing clutch drag which is hard on sycronizers. Having more discs also causes more inertia on the shaft. Warped floaters are common which cause drag and harsh engagement as well.
6. Heat capacity. Many times the multiplate clutches use real thin discs and floaters that get hot and/or warp quickly with the exception of course of the Carbon/carbon clutch.
7. Race parts. They are more meant for racing rather than street driving and not meant for slipping or smooth engagment, and the lack of inertia can be frustating in traffic.