chunky

***PLEASE READ THIS ENTIRE THREAD AS THERE ARE ISSUES WITH THE UNSPRUNG HUB*****

If you're looking for a smooth engaging clutch that can take the abuse of hard street driving, look no further. I had some issues with my car not wanting to shift smoothly after some spirited driving. The problem was intermittent so I figured it was the clutch and not the gearbox itself.

I took a gamble and only ordered a clutch disc since I was pretty sure the pressure plate was fine. The disc came from Clutchnet directly. I can't say enough good things about the guys there. I asked them if they had an RSX-s solid hub kevlar clutch in stock. He said "No, but I will make you one and send it out today." I had requested overnight service. There is definitely something to be said for a company that manufactures their own product instead of outsourcing everything.

It's essentially a full face clutch. With an unsprung clutch, the clutch will fit both ways, but the correct orientation is with the snout of the splines facing out and the flat side towards the flywheel.

Here you can see the construction. There is the kevlar friction layer, a cushioning layer and then the steel disc.

You can see here that my gamble paid off. I caught the damage early enough to prevent anything really bad from happening.

I can't say the Exedy stage I was a bad clutch. Sprung hubs and I just don't get along.

More parts = more stuff that can break. Unsprung FTW.

The 9lb flywheel.

Everything is set for the pressure plate.

Exedy Stage I pressure plate. Should have plenty of clamping force for my n/a motor. Kevlar discs do need a stronger pressure plate because of the material's friction properties.

She's in there, hopefully the last clutch I will have to install on this car. Kevlar lasts forever and there are no springs to break!


Honestly, this is the SMOOTHEST engaging clutch I have ever driven, bar none. Even smoother than the sprung Exedy organic disc. A lot of people are scared of unsprung hubs. This clutch engages ultra smooth with none of the jerkiness I would sometimes get due to the sprung hub. The clutch is so smooth for two other reasons, the kevlar material and the full face construction (no pucks). Major props to Clutchnet for offering this style of clutch and it's now my pick for the ideal street clutch.


Modified by chunky at 1:19 AM 2/14/2007

b19coupe

Nice clutch. Those crazy Russians at ClutchNet are good guys

BarracksSi

Awesome; never heard of those guys before, but it sounds like a good option.

Two questions:

Will this stress the clutch hydraulics any more than stock (pedal effort the same, etc)?

What would be an advantage of sprung clutch discs, anyway?

9bells

"What would be an advantage of sprung clutch discs, anyway?"

Less shock to the drivetrain.
The material used (kevlar) doesn't like to be loaded at the strip though,
soi you can't do that to minimize shock.
Just have to have good parts if you plan to launch on sticky tires.

I have to agree, my carbon/kevlar clutch is the best I've driven, even though it's sprung.

Mugen Dom

something i may consider

chunky

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 9bells &raquo;</TD></TR><TR><TD CLASS="quote">"What would be an advantage of sprung clutch discs, anyway?"

Less shock to the drivetrain.
The material used (kevlar) doesn't like to be loaded at the strip though,
soi you can't do that to minimize shock.
Just have to have good parts if you plan to launch on sticky tires.

I have to agree, my carbon/kevlar clutch is the best I've driven, even though it's sprung.
</TD></TR></TABLE>

I have to disagree somewhat.

An unsprung clutch doesn't really affect the drivetrain shock on a hard launch since the springs on a sprung hub will coil bind almost immediately. The springs are really there to smooth out the torque pulses from the crank. Supposedly this increases spline life for a street car. There are no conclusive numbers showing that splines last longer with sprung hubs.

The kevlar material this clutch is made of gets stickier the hotter it gets. In fact, I forgot to adjust my clutch pedal for the extra thickness of this disc when I installed it. I was driving around in some stop and go traffic and the clutch started to get heated up. It got to the point where I couldn't put the car in gear because the kevlar got grabby and the clutch would not release fully. I simply needed to adjust my clutch pedal and then the clutch would disengage fully even when hot.

Kevlar is a great clutch material, however you can glaze it if you're not careful so it gets a bad rap.

9bells

Fair enough, that's what I was told.
Had a similar experience...
Let the car roll out of the box,started to bog a bit. Put the clutch in,roll close to beams.
Only thing was it had gotten hot from rolling-out of the burn(I'm and idiot)
in 2nd. The thing would grab 1mm off the floor, really threw me off.
Redlit and bogged because it grabbed instantly. Oh well, learned.

chunky

Sadly, I have to withdraw my earlier recommendation of this product. The splines on the hub don't last longer than 500 miles. The story is as follows. I installed the clutch, drove it locally for about 200 miles, deemed the car road worthy, and embarked on a 600+ mile drive from Atlanta to Baltimore. In North Carolina, near Durham, the car broke down. I was cruising in 6th gear and the engine all of a sudden made a grinding noise and the revs would climb but the power was not transmitting to the wheels. The car gets towed to the nearest Honda dealership. The Honda dealership tells me that the transmission needs to be replaced. I ask them if they've drained the transmission fluid. The service adviser lets me speak to the tech. The tech says he'll call me back in 10 minutes. Ten minutes later I go from needing a new transmission to "most likely needing a new clutch." Their final diagnosis was that the clutch release bearing was the source of the problem but that the clutch disc itself needed to be replaced. I asked for pictures but they were unable to provide them. Going on their diagnosis, I ordered a new release bearing, new clutch disc of the same variety, new pressure plate, new clutch fork, and new pilot bushing. I asked them to save all parts for me to inspect. The car is repaired and I come to pick it up. One look at the clutch disc and my stomach churned. I asked them again if they were sure that the damage was caused by the release bearing as the release bearing was not in the box of used/damaged parts returned to me. I was unsure as to how the release bearing could have anything to do with the splines on the hub stripping out. The service adviser said the release bearing was badly damaged and that's why it was not returned to me but that their best technician had worked on my car and that the repair was sound. I paid $1070.22 for parts and labor - not including the new unsprung hub clutch disc and pressure plate I had overnighted from clutchnet. The total seemed a bit high to me. I looked it up later, and they charged me for 10 hours of labor on a clutch swap. Clutch swaps book at 6.6hrs of labor. The uneasy feeling got worse. After having the car for only 2 full days, on the 3rd day, the car broke down again. Same symptoms. Grinding noise, no power to wheels. I call dealership. Dealership tells me to bring my car in. I tell them that my car is undrivable and located in Baltimore. Dealer says to take car to nearest Honda dealership. I call nearest Honda dealership. They say that if I bring the car in, I become liable for diagnostics and that the original honda dealership that worked on my car needed to pre-arrange for my car to be delivered to them. I call the original honda dealership back. No return call. This goes on for a week. I decide I've had enough and I filed a complaint with Honda corporate regarding the misdiagnosis and superfluous labor charges. So we'll see where that goes.

ANYHOW, regarding the actual product, this is what I have to say.

I haven't really played around a whole lot with various clutch setups so it's been a learning experience for me. I have discovered some things about the possible cause of failure for the hub. In short, the hub does not offer enough spline enagement.



I sent the damaged disc pictured on the left back to clutchnet. After inspection they immediately made the same observation I had made over the weekend. The picture above shows the flywheel side of the clutch discs. On the left is the clutchnet unsprung hub, on the right is an Exedy stage I organic disc. The obvious difference is that the Exedy disc extends back towards the flywheel about 6mm. The overall length of the splines is about 27.5mm. A little math tells us that the clutchnet unsprung hub has about 22% less spline engagement than the exedy disc. I asked clutchnet if they could make me a disc with an unsprung hub that offers the same spline engagement as the OEM style sprung hub disc. He said that it's not really possible without paying a lot and will require time. They have agreed to send me one of their sprung hub kevlar discs which do extend backwards from the disc surface towards the flywheel like the OEM style sprung hub disc. I hope this will get me up and running.

Anyhow, I'm still a bit surprised that the unsprung hub failed so quickly considering that it had 80% enagement. I thought about it a little more and realized that having the splines terminate on the plane of the disc itself is a bad idea. Maximum shear forces occur on the splines on the plane of the disc. The weakest point of the splines are at the ends where they terminate. So putting the end of the splines on the plane of the disc is putting the weakest part of the spline where the most strength is needed.

Hopefully at some point in the future clutchnet will revise their unsprung hub design and address this issue. I keep saying it, but I really liked the unsprung hub kevlar clutch. I wonder if the exedy unsprung hubs could be bought from Exedy and fitted to the clutchnet disc. I'll have to chat with the boys at clutchnet about that one the next time I call them. Thankfully they've been very reasonable with me through all of this.

The honda dealership that fixed my car is a whole different story. . . . they misdiagnosed my car and then didn't return my calls for a week. I've given Honda's corporate offices a call as well as doing a chargeback through the credit card company. I'm a very laid back guy until I feel like people are jerking me around. Ignoring my phone calls for an entire week is one way to get me fired up.

Mugen Dom

thats rough man

chunky

I received the clutchnet sprung hub disc today. I had a small scare with it, but I think everything will work out.

The scare was that the clutch net hub has shorter splines than the Exedy disc. However, upon close inspection of the Exedy disc, it became apparent that part of the Exedy splines were not used (similar to how on the unsprung disc, part of the splines were not used).

Here you can see the wear marks where the splines ended.

recording the depth of the Exedy disc.

Dun Dun Dun, you can see why I was scared! There is a significant difference in overall length.

Here you can see how the wear marks of the Exedy disc coincide with the length of the splines on the clutchnet disc.

Another view of the same.

The clutchnet kevlar sprung hub disc.

Fully encased clutch springs, and made in the USA.

You don't see this design repeated because it's Patented!

And the most important aspect, the splines do in fact extend back from the plane of the disc towards the flywheel!

Another shot of the same.


So all in all, I hope this disc will work out for me. It seems like the next best thing to the unsprung hub.

Mugen Dom

looks promising...keep us updated would like to see what happens next...gonna be needing a clutch here soon

loading...

great thread...

95turboeg

Damn I have heard nothing but good things about clutchnet, My friend had a 6 puck unsprung on his 400 whp Nissan SE-R, and all grip, no slip.... Great clutch, we used to launch that car off the rev limiter and it held fine.

-Brax

chunky

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by brax90si &raquo;</TD></TR><TR><TD CLASS="quote">Damn I have heard nothing but good things about clutchnet, My friend had a 6 puck unsprung on his 400 whp Nissan SE-R, and all grip, no slip.... Great clutch, we used to launch that car off the rev limiter and it held fine.

-Brax</TD></TR></TABLE>

Well, I'm guessing that since I'm one of the first if not the first to buy a clutchnet unsprung hub for the k-series, this issue probably has not affected many clutch buyers. The sprung hub will have about 30% more spline engagement than the unsprung will, so that alone may make all the difference in the world.

Note that I'm not saying anything negative about clutchnet. Thus far their support for me after the purchase was made has been good. It's one thing to have something go wrong with a product, and it's another to have something go wrong and the manufacturer leaves you high and dry. Clutchnet is doing their part so I've got nothing bad to say.

BarracksSi

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by chunky &raquo;</TD></TR><TR><TD CLASS="quote"> Clutchnet is doing their part so I've got nothing bad to say.</TD></TR></TABLE>

I'd call this an experimental phase, then. This was their first K-series clutch, right?

chunky

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BarracksSi &raquo;</TD></TR><TR><TD CLASS="quote">

I'd call this an experimental phase, then. This was their first K-series clutch, right?</TD></TR></TABLE>

they've sold some of their sprung hub discs is what they told me. I saw one brand new being sold on CRSX not too long ago. I'm probably the first to use & install one of their kevlar discs on a k-series though.

chunky

That's what I saw when I removed the gearbox this time. The gearbox was a pain in the *** to remove b/c the remaining spline of the disc was no longer aligned with the splines of the mainshaft. That was the hardest part of the entire job.




It doesn't take much to see that significant portions of the mainshaft were not engaged by any spline. Look at the shiny part where the damaged clutch hub shined up the mainshaft. This confirms my idea that the rearward projection of the splines is absolutely critical in a k-series clutch application. I also measured my flywheel's disc mounting surface relative to a reference point on the block. The 9lb aftermarket flywheel that I am using is within &lt;1mm of the stock flywheel's friction surface. There's no chance that the flywheel affecting the position of the clutch disc along the splines - this is definitely a design compromise present in ANY unsprung disc that does not have splines that project fore and aft of the flywheel.



There's a little sketch I drew up to explain why I think that having splines on both sides of the disc is doubly important. I'm sure honda put the position of the disc where they did for a specific reason. It allows there to be equal spline on both sides of the disc.





Just as ACTman has suspected, there was an additional contributing factor. I'm definitely thankful that he kept repeating that throughout this thread otherwise I may not have ordered a pilot bushing to have on hand just in case. Afterall, the honda dealership was supposed to have replaced it. Needless to say, the bushing was fucked up. not a drop of grease on it. The dealership did mention to me that there was some damage to the snout of the crank. I asked specifically if it was the pilot bushing. The tech said no, it's damage to the crank itself. I'm very disappointed in this particular dealership's work. I specifically told them to replace the pilot bushing. Called and gave them the Honda part numbers. They still didn't replace the bushing.

As ACTman alluded to before, for the splines to strip out as they did in less than 500 miles, there had to be a bigger issue at hand than just the amount of spline. The amount of spline that was engaged should have lasted me for a few thousand miles before they stripped. With the design of the hub as it is, I doubt I would have made it past 5k miles even with a good pilot bushing.





And here we have everything re-installed. (the flywheel was removed to take measurements with the stock flywheel, note the blue loctite =P)

I made sure to grease up EVERYTHING. The freaking BRAND NEW release bearing was squeaking like crazy before because honda did not lube the pressure plate fingers at all.

I'll post an update when I get more miles on the car. However, I think all my clutch troubles have been sorted out. It's been a definite learning experience. I actually took measurements of how much spline was engaged/not engaged as well as the overall length of the splines. After collecting all that data, I'm pretty confident that the clutch net sprung disc will work out for me.

I haven't launched the car yet, but I have redlined it with a few high rpm shifts. The clutch engages quick, almost as quick as the unsprung hub. Slipping the clutch when starting from a standstill is infinitely better than with the stock or exedy stage I clutch. Very close in feel to the unsprung disc, but the unsprung was definitely more direct.

At any rate, I'm just freaking happy to have my car back on the road.