Getting a new clutch soon, I just wanted to hear some recomendations, war stories, or just what info you people have. Any info is always good info.

My application will be daily driver + track days + autocross (BSP scca).

I have always leaned towards ACT in the past. I am interested in trying somthing new. Like I said, any info is good info.



Lee

I would suggest sending a PM to Charles R Hill. He'll not only answer all your questions but his company , BHR, can sell you all the parts you need.

I got an exedy stage 1.. the pressure plate clamps down a lot stronger than the stock.
So it does feel different but after about a weeks use i got the hang of it. I wouldnt recommend getting anything higher than a stage 1. Seems like it would be a PITA for a daily driver. IMO .. and i also purchased the kit from Charles

Well guys, thanks for the info.
I am going to try an exedy stage one per your recomendations.

It is nice to see that there are peoiple with usefull info in car forums again.:hahano:

talk to BHR. they will take care of you. im very satisfied with my clutch/flywheel combo

The interesting thing here is that for the stated driving the car will be seeing, the factory clutch is well-designed. I have about 70K miles on my factory clutch and that is with much nitrous/drag use.

Lemme repost something about clutches in a minute........

Most performance clutches for the RX-8 will handle 300+ lb./ft. of torque at the flywheel and, just out of my own preference, I don't use percentages when thinking about driveline losses. The OEMs use percentages as a target when they are developing a new vehicle platform but, once that target is attained the percentage is moot. As such, I typically use 40 h.p. as a driveline loss figure for RX-8s with factory flywheels and 25 h.p. loss when using 9-10 lb. flywheels. SpeedSource, from what I have heard/read, uses 33 h.p. as a driveline-loss figure but I am not sure if they are were using a factory flywheel in that particular case or not. This is NOT to imply that a 9-10 lb. flywheel will result in a 15 h.p. gain at the rear wheels. It is only to say that I use these numbers as a vague way of predicting power numbers one way or the other.

Anyway, Exedy is sometime vague about the specific torque levels their clutches will handle but they do express the clamping force of their pressure plates.

ACT will mention the torque-holding capacity of their various pressure plates.

SPEC also mentions the torque-holding capacity.

Clutch discs are not generally chosen for their torque-holding capacity because they are actually dealing with heat-containment. As an example, Indy cars built using the Honda powertrain actually use off-the-shelf Honda discs. They can do this because their chassis only weigh, what, 1,500-1,700 lbs. or so? (I have a friend who works for Ilmor and they build engines for Indy, Champ, Nascar, and Off-Shore racing teams and we discussed all this. He knows what goes on and I tell him why, from a business perspective. Nice to have friends all over the place, eh?)

I will start to whittle it down to specifics in a few.........

Exedy has a couple different pressure plates for their standard diaphragm-type clutches, the "A" and "AHD". The "A" has a clamping force of 1,395 lbs. and the "AHD" is 1,455 lbs. These two pressure plates are used in their "10803" and "10902/10952" (Cerametallic) applications. I can only assume that the factory clutch has a clamping force in the low 1,300-range. Confused yet?

If I am allowed to move forward with my assumptions, we see torque-holding capacities for the Exedy stuff roughly in these ranges;

Organic disc kits;
1) Factory clutch, #MZK1002 or #MZK1006, 230-240 lb./ft.
2) Stage 1, #10803A, 260-270 lb./ft.
3) "MazdaSpeed", #10803AHD, 290-300 lb./ft.

The Cerametallic applications have rather harsh engagement and they tend to chatter in street applications. Remember, discs deal with heat (slippage during takeoff) and, although ceramic-type discs will handle more heat, street applications do not demand this level of heat-containment.

Ceramic disc kits;
1) #10902A, "Thin" disc, same pressure plate as the 10803A.
2) #10952A, "Thick" disc, same pressure plate as the 10803A.
3) #10902AHD, "Thin" disc, same pressure plate as the 10803AHD.
4) #10952AHD, "Thick" disc, same pressure plate as the 10803AHD.

Since we have Exedy's ratings as a basis, and ACT uses them as their own starting point, we can then take a look at ACT's own website for guidance.
Taking a look at this link we see the following pressure plates, street discs, and race discs (left-click on the bar graphs in the upper right corner);

http://www.advancedclutch.com/products/clutchkits.aspx

Pressure plates (percentages are ACT's estimations for comparitive purposes and values are at the flywheel)
1) SP, "Sport", 20-40% torque-holding capacity over stock. (280 lb./ft., +/-)
2) HD, "Heavy Duty", 40-60% over stock. (330-376 lb./ft.)
3) XT, "Xtreme Duty", 80-120% over stock. (423-517 lb./ft.)
4) XX, "MaXX Xtreme", 120%+ over stock. (517+)

Street Discs
1) OO, Stock Street. This one is a stock replacement, full organic.
2) MM, Modified Street. This one I am not sure which materials are in it and ACT isn't clear about it. My guess is that it may have a little Kevlar material to help with heat a bit.
3) SS, Performance Street. This disc contains copper strands as well as whatever is in the MM disc and is actually a pretty sweet disc.

Race Discs
1) R4, 4-pad.
2) R6, 6-pad.
3) G4, 4-pad, sprung.
4) G6, 6-pad, sprung.

All these "Race" discs have cerametallic or other exotic materials and are NOT suggested for any street driving.

By looking at the link above we see up to 20 different pressure plate/disc combinations offered by ACT but not all combos are available for all platforms and for 99.9% of us on this forum our needs can be covered by these following combos (ZM8 is the prefix designation for the RX8 application)

(Model-Pressure Plate/Disc)
ZM8-HDMM, 40-60% over stock.
ZM8-HDSS, 40-60% over stock, better heat handling.

The ONLY thing I do not like about the ACT kits is that they include the lousy Koyo release bearing and many of us know how poorly those bearings handle even factory pressure plates. IIRC, they DO include the pilot seal, which is a plus, as well as the pilot bearing and alignment tool. Exedy does not include the pilot seal.

Hey Ray, what is the difference between thick and thin pressure plate disks? Do the thin plates dissipate more heat?

Hey Ray, what is the difference between thick and thin pressure plate disks? Do the thin plates dissipate more heat?

To be honest, I haven't really looked into it because the cera-metallic discs, themselves, are not good for anything but the hardest-core of racers.

wow,

killer info.

to leemoshuffle

i have a exedy stage one clutch. that has less than 10% wear on it. comes with a brand new bhr throw out bearing. long story.

you win.

send me a pm.

beers :beer:

wow,

killer info.

to leemoshuffle

i have a exedy stage one clutch. that has less than 10% wear on it. comes with a brand new bhr throw out bearing. long story.

you win.

send me a pm.

beers :beer:

Long story, indeed. And you guys wonder why I don't do "killer" deals anymore.

Wow, thank you for all the info.
It is much appreciated.

I may have not mentioned that I can hear thepilot bearing is beginning to
tear itself apart.
I know the stock clutch is pleanty strong for the app. However, later when i decide which
power adders to use. Or maybe a 20B. I will need a stronger clutch.

Again, Thank you so much for the info.


Lee

the 92-95 RX7 have a problem with the act heavy duty pressure plate, they will bent the fork or wear the pivot ball. I don't know if the RX8 did the upgrade on those parts yet.
you should get the flywheel at the same time while you do the clutch.

Different clutches.

Charles, would it be safe to assume you recommend the ACT SS Street Disc? My car is stock for the moment but will eventually have a few power upgrades. I'm looking to replace the clutch and pilot bearing as soon as possible and just need a lil advice as to what to get. Thanks.

Ludo

I've been running the CenterForce Stage 2 clutch for about 30k miles now and absolutely love it. The pedal feel is about the same as stock but the engagement is much better. I really like it so far, it's a very snappy clutch which throws some that have driven the car off since it doesn't feel like it's going to be.