Rob Edwards

Just got back from a test drive, then brought the car home from Greg's. All I can say is that the old clutch has to have been slipping more than I appreciated, this carbon clutch frickin' lays down the power.... It literally accelerates like a different car. Of course there's no more power than there was last week, but the whole setup just feels better.

I am really happy with the outcome of this carbon clutch install- pedal effort is exactly right- marginally heavier than the too-light DD setup I had before, but way lighter than the new-ish single disc setup in my GT. I was worried about what engagement would be like after watching Anderson leap around the parking lot with his Tilton, but the clutch can be modulated perfectly at 1200 rpm and gently leave the line. Do it slowly enough and you can get underway without touching the gas.

There is a tiny amount of chatter in reverse (there are 6 friction surfaces that need to be mated in, I just can't bring myself to do the RPS-suggested break-in: Clutch dump at redline, x2....), and one can hear the floater plate a bit when stopped with the clutch in, but I suspect that'll all settle in with time. The other suggested break-in method is to roll near the torque max in 3rd gear, and go WOT while slipping it a bit with the pedal.

Anyway, count me as a happy camper- anyone considering one is free to test drive if/when you're out this way.

Danglerb was at Greg's too, but turned down a ride today- Mike, don't you like my driving?

GregBBRD

There's no question that this clutch exceeded both my goals and my expectations. And as most of you know....I have very lofty goals and am pretty darn hard to please.

The "amount" that the beefed up dual disc clutch must have been slipping, without really slipping so much you could hear the slip must be very significant. The "bofore" and "after" transformation is amazing.

When Rob says this is a completely different car to drive, he's not just trying to rationalize spending money on this new clutch. The car went from "fast" to "stupid fast". I drove it around yesterday and the thing is bordering on unsafe, when you mash down the throttle. Anything that will go "sideways in the street" at the top of second gear is silly...especially with the tires that Rob has on it. I suspect that this car is going to need a set of BFG Drag Radials to tame it down....

So, we need to get a few more miles on it, but it appears that we have a new flywheel/clutch, which is designed primarily to be smooth on the street, but also work great on the track, that will "hold down" 700 horsepower (the same clutch pieces that are installed in this application hold down 700 horsepower on other RPS applications.) Another pleasant surprise is that we actually have enough "room" in the bell housing to fit another disc...to make a clutch that will "hold down" way over 700 horsepower in a 928, which, of course no one has done....so we don't need to build that, right now!

danglerb

Not your driving, my back, swapping the batteries around in my two did not agree with it, so in/out in cars or bumps are getting avoided.

Besides you came back so happy somebody screaming in the seat next to you might have distracted from the moment.

Rob Edwards

Update- have put a couple hundred miles on this clutch- one of the things that is very different with this clutch vs the DD setup is that low-speed, low rpm driveline windup is much reduced. If you are in 2nd gear at 12 mph, stuck in traffic, and are getting just barely in and out of the throttle, the old drivetrain would wind up and lurch badly. I can’t make this car lurch now. It’s not like the old clutch was slipping under those conditions. Honestly I have no idea whether it's the clutch, different driveline masses, or ??? Perhaps it’s the superbearings in the TT better locating the driveshaft and damping the effects of windup(?). Whatever it is, it's 100% better.

Anyway, without the slip I'm finally really exploring what this car will do- third gear power-on oversteer is fun! I wish everyone with power-adders and a 5-speed could A/B this clutch vs. the DD setup. SO much better...

IcemanG17

This improved clutch is VERY appealing.....I am considering it for my racer at the same time my rebuilt (by Doc) trans is done..... Man that would be nice....a clutch that WORKS, a trans that shifts up and down + an LSD that works at more than 1/2 throttle.....man would I be happy

The only downside is getting approval from the "Boss"....but I am thinking I can pull it off by Sharktoberfest.....perfect excuse to get the car down there early to get everything installed...

Rob Edwards

Brian, you'll have to drive mine when you're here. It just plain _works_.

IcemanG17

DEAL......

My general impressions of 928's with left pedals is NOT GOOD.....

My widow had a stock GTS clutch (single disk) while it worked fine, it was blown in 6 track days....but I could shift gears....

The new car is a mess....so I drive it as a one speed....which is 1/2 the gears I used in the Estate, with its super reliable autobox!!!! I hope adjusting the intermediate plate improves things...

Jim R.

Any updates on how this clutch is holding up?

My clutch is slipping, and am looking at the current options for a winter replacement.

So far, absolutely smoked a stock single disk...nasty slippage and smell in third.
Have been using a Kevlar single disk with a heavier pressure plate for a while now, but it is starting to feel real "soft" on shifts and just mashing it.

Any further feedback from end users here?

Still in the $4k range?

And last, is this a DIY bolt on for a currently single disk car?

Thanks,

Jim

IcemanG17

update??????????????

Its still on my "list"..............but my current dual disc is working good enough.....it only drags after a session on track.....I come in the pit, get my tires measured and when I try reverse it will grind....1st will work, but the effort is much higher.......

Still I will have one of these eventually....

GregBBRD

Jim:

They have been done and ready for sale. We've just been doing some further testing, to make sure they work as well as we think they do. Ed Standke has one in his supercharged track car and Rob Edwards has one in his street car.

Chatter, in Rob's street car is very, very minor and very easy to drive "around"...unlike a single "puck" disc. Only occurs in reverse, with "sloppy" clutch release.

They hold over 800hp, in the same configuration, in different vehicles. No one has tested them to that extent, in a 928! I can tell you this....there's not any slip, once they are engaged. Period.

We don't have long term data on wear, but in the same configuration, in different vehicles, they last for very long periods of time. All of the surfaces are carbon...which wears slowly.

They are priced at $3995, for this first "batch". They consist of a new steel flywheel with a carbon surface, two carbon discs, a carbon intermediate plate, and a carbon pressure plate. They are "push" clutches and are activated by a hydraulic Tilton T/O bearing, which is included, along with the required lines and the mount for the T/O bearing. A pedal stop is required and we supply Porken's clutch stop. A redesigned pilot bearing is included. Minor modifications are sometimes needed on the very end of the crankshaft (simple 90 degree hand grinder with sanding disc) and slight modification to the "short" input shaft (need a lathe or an external grinder, for this.) Eventually, we will be making higher strength "short" input shafts, made to the correct specifications....but if I dream up another product to make for these vehicles, right now, my wife is going to have a cow! (These input shafts will also fit stock applications, BTW.)

The "stock" T/O arm is no longer needed, along with the entire stock flywheel and clutch package. The T/O guide tube is also no longer required.

Installation is similar to installing a stock clutch, the exception being that the bell housing needs to be removed for a minor hole for the clutch line to pass through and needs to be off to mount the flywheel. Bell housing removal is fairly easy on a stick shift vehicle. I simply remove the entire torque tube, for easy access.

Complete instructions are included.

Jim R.

Thanks Greg, sounds good. I'm used a little chatter in reverse now. Sounds more "street friendly" than the spec 3+ .

Very nice piece of hardware!

I'll be in touch, looking to do this over the winter. Usually put the car away in December.
Hopefully it holds up till then.

Jim

xschop

Had to use Google to find this thread. What power is this pusher clutch setup holding? What is the Diameter (OD) of the disc?

GregBBRD

The dual disc is rated, conservatively, at 750 ft.lbs., rear wheel.

If you need more, we have a triple disc version, that I made up, in the developmental phase.

The most we have "fed" through a dual disc one, in the 928 application, is about 450 ft. lbs.

The discs are 9.25"

Let me know if you need any more information.

GregBBRD

Good news, for all 928 owners.

As many of you might be aware, 928 stock clutch parts are getting "shorter" in supply.

Since my dual disc version of my 928 clutch works so well:

I designed a single disc carbon-carbon clutch and will have them ready for testing, by the end of winter. The manufacturer has many single disc clutches, like this, already being used. They conservatively hold 400 ft.lbs.

Same idea. This clutch will also be a "push clutch", so absolutely none of the stock pieces will be needed and the clutch will be fully rebuildable.

terry gt

Greg , A single disk clutch sounds intresting , my stock clutch in my GT might be slipping , what power will the stock clutch hold ?