RB Flywheel resurfacing step

[Tofubadguy]

Tried to go together with my RB26 and transmission last night. Had to pause though for more information.

I'm looking for the factory step depth between the surface the pressure plate bolts to and the surface the clutch disc runs against.

I'm using a standerd single disc factory style replacement pressure plate and disc from Competion Clutch. I've searched the forum and although there's lots of flywheel talk I haven't found this step measurement.

The flywheel I'm using isn't exactly stock and it's step is considerable. It had an old twin disc Greddy/Nismo setup (replacement discs no longer in exsitence) on it that looks like it won't accomodate a stock replacement profile pressure plate. So I want to machine the flywheel to whatever it needs to be so I can proceed.

Thanks!

[240z4u]

Find out what the 300zx step is, that's what was done for mine by the machine shop and it works very well.

[Darius]

That's the spec I had the machinist resurface mine to as well. (300ZX)

[Tofubadguy]

From what I'm reading about the 300ZX flywheels, .008" low on PP bolting surface is recomended for big power, and just flat across the whole surface is fine for most regular applications/ NA.

If this is the step you guys are talking about then I have a lot to cut! I didn't measure it late last night and I'm at work right now, but I'm guessing around .100" high on the disc wear surface. Which is kind of cool though because it will make it a little lighter too.

I'm going to keep looking for some official print about it, but that is starting to make sense.

[240z4u]

You can do all the looking you want, but honestly man the z32 step is the one everyone uses because they are using a z32 clutch! Are you saying your flywheel is worn down .100" on the friction surface area? I don't think I would reuse that flywheel at all.

[Tofubadguy]

No it's not worn at all. I had a skim cut taken from both surfaces when I had planned to find replacement discs for the Exedy/Nismo twin disc pressure plate combo. The step is intentionally higher (clutch disc surface) than the pressure plate bolting surface. How the stack up of the twin disc assembly was needed this step.

Those Exedy disks are not available anywhere, so I checked the pressure plate bolting patern on the flywheel was the same as a stock flywheel and it is. So I figured why not just use this flywheel scince it's considerably lighter than a OEM one, but still has the basic (active side) profile, and a lot of meat missing from the dummy side (block side) compared to an OEM. Seems like everything should work well if the .100" step is cut down to a very small .008", or non step, to use this factory style replacement single disc setup.

Regardless if it's for an RB or a 300 I'd still want to see something in print other than a couple posts on other forums copy pasting each other by whoever they are saying cut it flat or use .008", which is so far all I've found.

Doing a mixed combo of parts like this I need to be sure what I want and that it will work, as my buddy down at NAPA will only do what I'm sure of and ask for.
It's why I'm here and hoping to find a link to a manual, mechanical drawing, nissan print, etc... before I get too excited!

My NAPA guy says that his book lists from .005" to .008" for most of the 300Z's all through the 90's. So that's as official as I've found so far. But then I found this while searching as to the why...

http://www.zcar.com/prev_next,prev/90-9 ... 0.html#new

Re: Zazupilot - question on flywheel resurfacing
« Reply #9 on September 22, 2007»
Both of you are incorrect on what the step does. The step does NOT increase clamp load. It actually decreases it.
Its not much but it does decrease the clamp load.

On the old style coil spring pressure plates it would increase because your pushing the springs back more.

With a diaphram style plate it will decrease the clamp load.
As a clutch disk wares with a diaphram stlye pressure plate clamp load increases.
Bascially when you add a step to the flywheel you are making the disk "thicker"
-Spddracer

Re: Zazupilot - question on flywheel resurfacing
« Reply #10 on September 22, 2007»
Actually that statement may not be completely true either. Much of it depends on the fulcrum point and how much past the center line the clutch is biased. A diaphragm clutch will only increase in clamping force until the fulcrum has moved past a point of maximum clamping force. Once past that point the clutch begins to lose force again. The original clutch on the Z32 was designed so that the .008" step put the clutch at a point where normal clutch wear would maintain the pressure plate within it's positive clamping range. Without the step, normal clutch wear would take the clutch beyond the positive clamping range. The result is that you actually begin to loose torque holding capacity before the friction disc wear is out of spec. Accelerated clutch failure near the 3/4 ware point is the result. A very good friend of mine (GA Tech Mechanical Engineering Masters Degree Graduate) spent some time making measurements in order to verify this a few years back. This is based on the stock TT clutch dimensions. He's designed some quality clutches for various cars over the years with outstanding holding power. The reason he investigated this was in order to find out why Nissan incorporated the initial step as part of the design in the 1st place.
-JT240Z

Just wasn't ready to go into studying the diaphragm pressure plate design and what would ultimately be best. Suppose it wouldn't hurt me though! Sounds to me there is a bit of confusion on the schools of thought over more or less clamping force though and I'll be in hot pursuit of the reasons why. It sounds like the point of the second post was that the additional .008" was just to help keep the best range of clamping force through the proccess of normal wear. Sort of why I wanted to see black and white some official print. Thanks for any ideas or info anyone can provide!

[240z4u]

That's too bad the exedy is not going to be reusable. What are you going to use?

Have you considered looking in the *gasp* rb25det FSM? It's gotta be in there.

[Tofubadguy]

Yeah it sucks the older Exedy clutch can't be used. The only option I've found for it so far is to take the discs to an industrial brake and clutch lining shop, which there are 2 of in the area. I took the discs to Arizona Brake and Clutch around 2 years ago and they really seemed hesitant about it since the material was so thin compared to the industrial truck stuff they usually did. No warrantys or garuntees or anything. The counter guy said all they could give me was a 'good luck and hope it works'.

Which honestly may work awsome. But enough doubt in their mind to make me look at a different route.

I have my printed PDF FSM for my R32 GTR in 2 large ring binders. I remember instructions for the flywheel's general finish, clutch assembly and disc centering, but not on measurements or any mention of a step. I didn't look at it last night but I'll look again and see if there is any other place that would list a measurement or even mention it. Thanks for the reminder!

[Carl H]

no step.