Tim Suddard
Tim Suddard Publisher
3/3/22 11:55 a.m.
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When hopping up an early Mustang, like our 1965 vintage racer, usually you’d run a standard or lightened 157-tooth flywheel mated with a 10-inch clutch. In the past, we have used clutches from Centerforce and others and have had good luck.

This project would be different. Our expert, Curt Vogt, told us that for an all-out race car, we …

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Tom1200
Tom1200 UltraDork
3/3/22 12:16 p.m.

As always I have questions; what are the real world advantages to this set up?

I'm assuming the smaller diameter in effect works like a lighter flywheel and this clutch set up is less likely to slip.

Are the advantage worth the trade off? (I'm sure that answer will vary by user)

frenchyd
frenchyd MegaDork
3/3/22 1:17 p.m.

In reply to Tom1200 :

For racing absolutely. But••• do not drive it on the trailer or off. Buy yourself a winch.   Try not to get stuck in pit traffic. 
    Do not ever attempt to drive it on the street.   If I sound like I'm warning  you not to slip the clutch I am.   Those thin disks get real thin when you do. 
   If I'm not mistaken the Mustang is  going dog ring?   If so that's absolutely the application for a triple disk. 

Noddaz
Noddaz GRM+ Memberand UberDork
3/3/22 2:07 p.m.

No blow proof?  I realize there is less mass there to blow up, but...

fearlesfil
fearlesfil New Reader
3/3/22 2:54 p.m.

0.190" is "perfect" between 0.170-0.023 ? 

fearlesfil
fearlesfil New Reader
3/3/22 3:03 p.m.

Suggestions: 

"clutch forks" should read: pressure plate tongues, fingers or release levers.

The hydraulic throw out bearing replaces the conventional "fork"

Cheers!

Colin Wood
Colin Wood Associate Editor
3/3/22 3:41 p.m.
fearlesfil said:

0.190" is "perfect" between 0.170-0.023 ? 

Thanks for catching that. It's meant to read 0.230 and not 0.023.

"clutch forks" should read: pressure plate tongues, fingers or release levers.

The hydraulic throw out bearing replaces the conventional "fork"

Confirmed that "clutch release fingers" is more correct than "clutch forks" for this application.

mke
mke Dork
3/3/22 4:02 p.m.
Tom1200 said:

As always I have questions; what are the real world advantages to this set up?

I'm assuming the smaller diameter in effect works like a lighter flywheel and this clutch set up is less likely to slip.

Are the advantage worth the trade off? (I'm sure that answer will vary by user)

I have a similar clutch in the frankenferari.  I originally installed it because a single disc clutch that would handle the upgraded hp made the clutch pedal so stiff it was basically undrivable on the street.  With the  triple disc 7.25 clutch it will handle 800ft-ld torque with the softest spring they offer and the pedal is honda civic soft.  Huge improvement in dirvability.

The perfomance benefit is way reduced flywheel effect as you'd postulated.  The clutch much lighter but its also much smaller diameter and ineria is an r^2 term iirc so for me it ended up about 1/4 the inertia of the heavy duty single disc it replaced.

...and it looks pretty cool which has got to be worth about 100hp wink

Kendall_Jones
Kendall_Jones Dork
3/3/22 4:20 p.m.

Are we posting race clutches now? Cause I got a tiny one!

mke
mke Dork
3/3/22 4:32 p.m.

In reply to Kendall_Jones :

I didn't have the nerve to do a 5.5...the specs said it would be fine but I chickened out sad

Kendall_Jones
Kendall_Jones Dork
3/3/22 4:55 p.m.

In reply to mke :

And this one is a SINGLE plate clutch - most parts are NLA. I'm a little concerned myself! :)

Paul_VR6 (Forum Supporter)
Paul_VR6 (Forum Supporter) SuperDork
3/3/22 5:06 p.m.

I have had much better luck with uptake/driveability of the multi-plate clutches than the beefy singles.

Streetwiseguy
Streetwiseguy MegaDork
3/3/22 5:12 p.m.

A twin disc 5 inch clutch on a flex plate sure does make for a zingy engine.  And they sure are easy to stall pulling out of a parking spot.

stafford1500
stafford1500 GRM+ Memberand Dork
3/3/22 7:42 p.m.
Kendall_Jones said:

Are we posting race clutches now? Cause I got a tiny one!

5.5"? why so big???

From an IRL car circa 2005

alfadriver
alfadriver GRM+ Memberand MegaDork
3/3/22 8:08 p.m.

Tim

How did you attach the small flywheel to the flex plate?  Pretty clever solution, there- never considered using an auto trans flex plate...

stafford1500
stafford1500 GRM+ Memberand Dork
3/4/22 6:10 a.m.

In reply to alfadriver :

Typically, the flywheel bolts are replaced with longer parts and the button flywheel mounts in behnid/parallel to the flexplate. There are other ways, but this is the most effective way to transmit the torque straight from the crank to the clutch assembly.

dean1484
dean1484 GRM+ Memberand MegaDork
3/4/22 8:36 a.m.

Over the course of ownership of one of my FC RX7s the clutch and flywheel got progressively lighter. I did not have any real issues street driving it. Yes it was a little finicky on steep hill starts but generally no issues for me. However a couple other people tried driving it and they had a hell of a time.  
 

I would be curious if having it on a much higher Hp car will make it easier. 

gumby
gumby GRM+ Memberand Dork
3/4/22 8:53 a.m.
stafford1500 said:

From an IRL car circa 2005

So, that's what they're overcompensating for! A weenie 4".....clutch

Silver Crown clutch

stafford1500
stafford1500 GRM+ Memberand Dork
3/4/22 2:37 p.m.
gumby said:
stafford1500 said:

From an IRL car circa 2005

So, that's what they're overcompensating for! A weenie 4".....clutch

Silver Crown clutch

That particular flywheel, we had to cut the clutch cover in pieces to get it off the studs. It got overheated and the studs flared out in the process of warping the flywheel. They have the most beautiful transition to to bright blue at the top of the studs.

 Lesson learned: don't overheat the tiny little clutch/flywheel with too much slipping.

Randy_Forbes
Randy_Forbes New Reader
3/5/22 10:48 p.m.

I put the same clutch in an M Coupe for a guy, and swapped out his stock S54 for an increased stroke 3.4 litre one.  It was his dedicated track car, but never came to terms with the on/off clutch action and had it pulled back out.

With the extra-curricular work I did on the car, putting some test miles__40-50 anyway__on it was a given, and being in a somewhat rural area, driving it around here wasn't an issue.  I was also tasked with some brake diagnosis and bedding in some pads, so I had a bit of fun  with it.

The transport driver had no yearning to drive it onto the 5-th wheel trailer, for a short hop down to Active Autowerke to get tuned with it new CSL airbox, so I poppped it up the ramps for him!

mke
mke Dork
3/6/22 8:11 a.m.

In reply to Randy_Forbes :

Mine is a street car and there is no way I'd switch back to a standard type clutch.

 was I was pretty nervous making the jump, but tilton was saying their pretty new at the time (like..115-16 years ago?) carbon-carbon setup was ok for street use and a few people were running them so I said ok.  At the time they were the 3 disc 7.25 thinking is should have a better service life. 

Anyway for sure its more on/off than a stock clutch and carbon bites more the hotter it gets so if I heat it up it wants to be a race clutch.  It will also chatter a bit  when you let it slip too much.  When Someone new droves the car I just told them "the clutch is a little sensitive" and  none of the maybe dozen people who drove it had any issue or even commented on it.  The old clutch with the million lb clutch pedal they did comment on, it was horrible, I don't want that back.

One thing I did do is spend some time getting the pedal ratio as right as I could.  The clutch wants 1/4" iirc and that is all it gets with full pedal travel.  I have believe that helps on the street but maybe isn't what you'd want on a track car.

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
3/6/22 8:25 a.m.

In reply to mke :

I did a triple carbon/carbon clutch in an STI and the owner had us take it back out after a couple months because of how much it slipped.  The manufacturer went in the direction of ok drivability hot, slips a lot when cold.  The instruction manual that came with the clutch even told you to do a "clutch burnout" to heat it up before launching it at the dragstrip!

I think I have pics from forever ago...

mke
mke Dork
3/6/22 9:01 a.m.

In reply to Pete. (l33t FS) :

Interesting...mine doesn't do that at all, it does bite more hot but I've never had it slip cold.  With the spring I have, it's rated at 800ft-lb but the engine at that time was putting out about 450ft-lb so it could be I was so far from the line I didn't see it and maybe the real reason they were recommending way my clutch capacity than the car needed?   

The new engine will a bit high and in the 500-550 range I think so fingers crossed...it worked fine driving around the block with the engine barely running so more a testament to smooth engagement then holding power I guess.

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
3/6/22 9:02 a.m.

In reply to mke :

Interesting indeed.  I won't name the manufacturer because they are a prominent GRM advertiser and some may take it the wrong way.

IIRC the engine in the car made something in the 350 horsepower at the wheels (AWD) range at low boost.  Being a Subaru 2.5l engine,this would be all torque and no RPM.  The real reason we had the engine out was because the (rather expensive) tuner-built longblock was lifting the heads at 15psi (low boost) on the dyno.   I block-tested the cooling system at idle and never found any presence of exhaust gases.  It was early spring, cold, and rainy, and I did not want the liability of driving a car that powerful on summer tires under boost.  So, the owner offered to drive it, and I sat in the passenger seat.

40F, raining.  On UHP summer tires,  He casually opens the throttle in 3rd gear at 30mph or so, and without any noise, sturm, or drang, the gravitational forces acting on me stop pressing on my butt and start pressing on my back, and the world passing by speeds up like the Millenium Falcon going into hyperspace. 

That was the moment I decided I really needed a turbocharged all wheel drive car in my life smiley  Photo data says 2007, so it only took me ten years to get there.

Anyway, we put a ceramic multidisk clutch in and he was much happier.

mke
mke Dork
3/6/22 9:43 a.m.
Pete. (l33t FS) said:

In reply to mke :

Anyway, we put a ceramic multidisk clutch in and he was much happier.

I was always terrified to try that on a street car.  I remember looking and seeing "not recommended" on everything I looked at.....whci is not the same as can"t I guess laugh

This did prompt me to go have another quick look and I see the current version of what I have is still recommended for high performance street use....and is about double what I paid when I installed it about 2005.  This has me wondering about the car budget...every year its a fight to maintain the previous year's budget much less increase it, I don't think I could buy the clutch today sad

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