Carbon/Carbon Clutches - Single - Twin (not just for race)

I wanted share some info here for Legacy GT and Spec B owners. I have been doing lots of research into the clutch that will be going into my 2008 LGT Spec B (450/wtq or 380/wtq on E85) depending on which Mustang dyno and how it is calibrated. Also, i'm looking at future power enhancement when I need to replace/rebuild/renew the block, so the clutch will need to be able take the increase if necessary, as I may change the turbo too.

 

I originally was looking at Exedy Twin Plate HD, and was almost ready to get one, then heard about the RPS Max Street clutch, but then trying to find one was another issue, then I kept going back and forth between this and the Exedy Twin-Plate (pricewise, RPS is cheaper and holds just a much drivability is smooth, etc.). So I decided to wait and keep researching.

 

I am looking for a clutch that can hold and deliver the power, feel close to stock pressure, yet still retain daily drivability, PP and friction material needs to last and take abuse of the occassional track/strip hard launches and FFS, should be able to rebuild it if necessary, and finally, be affordable, and competitively priced from a reputable company. I know, it's a lot to ask...

 

I believe I have found that clutch that meets the requirements, but I want to talk about what I found out. I was looking at the Carbonetic (ATS/Across) carbon blade, but it seems that the only rebuilding part is the disc itself, and there is not carbon friction material on the PP or FW which is what carbon needs to react to limit the wear on the carbon disc. So, the Carbonetic carbon blade is not a true carbon/carbon clutch.

 

I looked into the RPS clutch and this seems to meet all the requirements. I contacted turboclutch.com (RPS), spoke to RJ Smith (son of the company) and he told me that they are now making and marketing the RPS single and dual carbon/carbon clutches under a different name. Some may have heard, but this was news to me.

 

When I inquired about the RPS Max Street, he mentioned the single carbon/carbon clutch.

 

"Another option that we have is a Single disc Carbon-Carbon clutch with a steel flywheel. This unit has a total weight of 32 lbs vs the 36 lbs of the factory unit. With the 32 lbs you will not have a miss fire code and the gear noise will be minimal vs other steel flywheel options. This clutch is rated for 600 ft/lbs and still has a stock like pedal feel. The nature of Carbon-Carbon is very smooth like the factory clutch. This clutch lists for $1,495.00..."

 

So, I asked for some additional info. and got it:

 

"Our Single carbon is built around the factory stamped PP. We replace the diaphragm spring with our Patented Heat Treated(HT) one and replace the cast steel pressure plate ring with a Billet Aluminum one. This ups the clamp load and removes 3-4 lbs from the pressure plate. Even with the HT diaphragm we still only have a 10% pedal increase. As Carbon-Carbon has to rub against itself we have it in the pressure plate and the flywheel. Both are screwed in making it easy to rebuild by you, the customer, if need be. We offer both a Alum flywheel or Steel flywheel option. The Steel flywheel is recommended for all street cars with factory ECU's as it weighs 32 lbs, which will not throw a miss fire code.

 

These clutches are being sold under the name SpeedSport Clutches. Our website is http://www.SpeedSportClutches.com and it is still having all the content updated."

 

As I found out, looks like they have offered this clutch for other popular vehicle/engines too, such as, WRX, BRZ/FRS, Mazdas, EVO, and Nissan 350Zs, SR20 and KA24DE.

 

Clutch cover for BRZ/FRS showing the carbon riveted to the aluminum billet PP face.

 

 

Flywheel side for the STi 6 speed.

 

 

5/22 - Update. Received the carbon-carbon single disc clutch kit for a 6-speed (Spec.B or STi).

 

 

Removed the cover to expose the rest of the clutch. Weight with the fully assembled clutch with T.O. bearing is a shade over 33 lbs.

Forgot to mention that I found out more details about clutch technology via these fine links, then started searching more until I found out about the Carbon/Carbon clutch:

 

http://www.formula1-dictionary.net/carbon-carbon.html

 

http://www.formula1-dictionary.net/clutch_road_car.html

 

http://www.hotrod.com/techarticles/drivetrain/hrdp_1005_new_disc_clutch_system_news/viewall.html

 

http://www.turbomagazine.com/tech/0407tur_clutch_tech_basics/

I guess this is just too bleeding edge? No one has any comments? I'll probably have to be the guinea pig. I can get the clutch with steel FW for around 1200 from MVP Motorsports. Tempting.

 

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No just wish i saw this last year when replacing my clutch.

subscribed!

Well, I pulled the trigger today and ordered the RPS SpeedSport Single Carbon-Carbon with Steel FW from MVP Motorsports. I'll provide impressions and feedback after I get the clutch installed, hopefully this weekend.

Sweet let us know.

So after over a month, the clutch has finally arrived, i'm picking it up tonight.

Well keep us informed. my biggest curiosity is life span.

Sorry I just read this, we had a RPS twin disc clutch in the race car. My son did lots of research and chose them. You should be in good hands.

Correct me if I'm wrong.... But didn't RPS make some of the first clutch kits around 2005 for these cars... and they lasted less than 1000 miles for most people? I'm pretty sure I had one of those. It was garbage.

 

Save some money and get an ACT clutch with the 6 puck sprung disc. It'll hold the power and it drives fairly nice.

Yeah RPS made some terrible clutch kits for these cars originally, but it was technically a conversion, so their carbon clutch may be better. 32 lb. flywheel for an aftermarket clutch system is a lot! FWIW I run a 14 lb flywheel and have 0 misfire codes. The 32 bit Subaru ECU is pretty good about handling a lightweight flywheel. That said, I do not recommend running any flywheel under 10 lbs. My 6-speed ACT full face disk is rated for 505 ft lb. I haven't done any hard launches yet but quick shifts show the clutch grabs hard and I am confident in its holding power.

 

I hope the RPS carbon clutch works well for you, but a sintered full disk like the ACT or a 6-puck may serve you just as well for a lot less money. If you were making 600+ wtq, then I could see the need for a multi-disc setup or carbon.

So I updated the original post with all the pictures of the clutch, as well weighing the entire clutch assembly. The clutch looks terrific, and I hope it performs as good as it looks. I went with the lightened steel flywheel to hopefully reduce noise and maintain smooth engagement and drivability.

 

Everything is included, and the clutch hub splines will need to be lapped prior to installation to ensure trouble-free movement, using the lapping compound and provided instructions. Also, there is blue and red loctite (red for the cover bolts, and blue for the FW bolts) as well as copper anti-sieze for the input shaft hub and splines (after lapping).

 

I hope to get this clutch installed and broken in before next weekend.

Very interesting, thanks for being the guinea pig.

 

I had an Exedy Twin for a while and it drove great, launched great, and put up with many many abusive launches. But after about 20k miles it just stopped disengaging, and apparently that's pretty common after 20-30k miles. The friction discs warp, it's $500 for new discs, and changing clutches is a pain in the ass, so I'm not really keen on that clutch anymore.

 

I have been looking for something that will launch well and last at least twice as long. Maybe this carbon/carbon is the answer.

 

I'm using an ACT HDSS for now, but I'm driving gently on it and still not really expecting it to last.

Google found a long thread from a Supra forum:

 

http://www.supraforums.com/forum/sho...ed-back/page10

 

Sounds like the carbon/carbon single drives OK. The twins and triples, not so much.

Just noticed this was a 6spd. Shoulda gotten an ACT or an Exedy single plate.

 

Enjoy your headache How much was it btw?

Installed the clutch on Saturday 5/24 @68180 miles. I went to Pit Row in Santa Clara, Ca to rent the lift bay and tools. I could have pulled the motor but instead I opted to pull the tranny. The job took me 8.5 hours as I work slow and didn't want to break or forget something. The old stock clutch shows that it was slipping.

http://img.tapatalk.com/d/14/05/27/y5aqa2y8.jpg

 

Yesterday, I put a little over 100 miles on it. Initial feel is a slightly stiffer pedal, like any HD pressure plate. The clutch does not exhibit any shudder or chatter and slips like a standard organic disc clutch. The engagement feels like the stock one as far as shifting and release of the pedal. There is no off-on feel similar to or like puck style disc and you don't have to rev the engine either to smooth out engagement. There is only a slight amount of transmission noise on low speed deceleration in first through third which is what I had with the stock clutch.

 

Update later after 500 mile break-in and that will be before the track event that wpmarky has arranged on the June 1st at Sonoma Raceway.

 

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Sweet let us know.

So tell us... how has the new clutch been treating you?

So I have almost 1000 miles on the clutch it is a little more softer feeling than when originally installed, firm feeling, not stiff. Maybe I got used to it, but it is not horrible as a daily.

 

The clutch can be slipped and it's better to slip it at about 1200-1500 when first engaging it, else at very low RPM it will shudder, feel lumpy, maybe just a bit juddery and so to smooth it out it needs to be slipped. This is probably due to the disc not being sprung and the carbon-carbon friction.

 

It grabs terrific during launch and shifting gears at any rpm it is very easy and smooth like a stock clutch. On the track, it was superb. Daily driving is fine in city traffic.

 

Minor annoyances:

It is a little noisey at deceleration in 1-3 in low speed.

Also, the starter makes a little bit of a whine during startup on the ring gear of the FW.

 

Now will have to see how it holds during longevity.

 

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Only a 1000 miles in 2 months, you need to drive more.

 

Keep us updated.

 

Thanks,

update

Updates?

Drove the car from San Jose to Willows out to Thunderhill Race Park for a two day track event and the clutch is grabbing and holding like new. Mileage is 70800.

This will be my next clutch when i wear out the oem sti one.