Slave cylinder travel distance

[jdwertz]

I had looked into this last winter when I was having issues with my own 9k clutch setup in my c900. I kept popping brand new slaves. APRacing themselves were not very helpful in regards to price since they only sell through dealers. I called every US dealer listed on their website until someone came up with a price for me. They were available last year and in the mid $500 range. Even though they are expensive it seems like it will be the last slave you will ever have to buy. Their seals are square section seals rather than the stock O ring seals.

Here is the email I received from their engineer:

Dear Sir,
My feeling is that you may be popping the seals because from memory the seals are “O” ring type. In our cylinders we use the same square section seals that are fitted to the brake calipers. I have attached a couple of drawings above for 2 versions, one is as fitted to the Saab 900 ( CP3959 ) and the other is the Saab 9000 type ( CP3859 ). The details of the Saab part numbers are shown in the bottom left hand of the attached drawings. I think that fitting the 12,00mm stroke version is not the way to go, not only is it a short stroke BUT it is also shorter in length and the piston will definitely pop out of the body. My suggestion is to measure the new cylinder that you have and compare the details against those shown on the drawings. If you have any questions please ask. As we do not supply parts direct you will need to contact a distributor from the list attached above to order any parts.

[Nate]

It looks like the APRacing slave clyinder has a stroke of 18mm. This may be a solution if the stroke is longer than the standard slave clyinder. Does anyone know what that is?

[Sam]

What about just grinding off everything but the platform on the one you popped and using it to shim its replacement? Seems like this would be free and would also maintain hydraulic ratios between the two cylinders. I mean, it seems obvious to me that more stroke in the slave would require more in the master, or at the very least a narrower bore on the slave to build a bit more pressure.

Maintaining that 1:1 ratio between master and slave is surely better for pedal feel.

[Cark]

Now I'm worried... Dave has my 9k clutch and is supposed to be doing a flywheel for me. Is it just that he's taking too much off the flywheels here or what?

[DrewP]

Hard to say. I'm still on the slave I put in the car almost 10 years ago, and nobody has measured any of them.

I also didn't know some of the different brands of metal parts were different.

[Sam]

Dave does awesome work, I would not worry about it one bit. It is really the 6 puck disc which made the installation hard. If i needed another one done i would go back to him 100%. Luke also has had good experience with him.

[Jon1]

My experience with Dave has not been that good. ....

[Crazyswede]

Dave's does great work, you just might have to wait a year or two to take delivery of your product.

[Cark]

Nate what did you end up doing here?

I just installed my Dave built 9k clutch on c900 flywheel setup yesterday. It looked like the travel distance on the slave was going to be very far before it hit the pressure plate, but turned out once we got it blead the pedal feel and throw is perfect! Drove 106 miles home no problem and I'm now back to daily driving my 85 with it's fresh(er) motor.

[Nate]

I remeasured everything and I was WRONG. With the new setup, the slave cylinder actually has to travel about .100" less than with the stock setup. It was just bad luck. I have about 1k miles on a new OEM slave. No issues now. Sometimes a slight grind in 1st if I try to engage it with the car rolling. I assume that it is just a quirk of the c900's.

Nate what did you end up doing here?

I just installed my Dave built 9k clutch on c900 flywheel setup yesterday. It looked like the travel distance on the slave was going to be very far before it hit the pressure plate, but turned out once we got it blead the pedal feel and throw is perfect! Drove 106 miles home no problem and I'm now back to daily driving my 85 with it's fresh(er) motor.

[Cark]

Thanks for following up Nate! And yeah, 1st I ALWAYS make sure I'm to a full stop before engaging.

Glad to hear it was just a fluke and not an error on Dave's part. Dude knows his shit.

[IronJoe]

I am having a similar issue in my car. Just replaced the previous clutch setup with the following:
'91 9000 2.3 Flywheel, resurfaced
Spec Stage 3 9000 clutch kit
New throwout bearing & pilot bearing

We bled the clutch multiple times, and still it is difficult to engage gears. Diagnosis was that there was some problem with the clutch disk not fully disengaging, which would point to the differences in height of the pressure plate and thickness of the flywheel itself. At this point I am thinking either there needs to be a thicker throwout bearing, or the slave cyl needs to be shimmed.

Any other ideas/opinions?

[IronJoe]

Looks like my problem is solved. I took apart the clutch and didn't see any problem with its operation. Turned out I had not accurately adjusted the shifter linkage when installing the new transmission, which was causing the issue.

[DrewP]

Huh. Was it in every gear, or just some? I forget what year your car is, does it have the earlier style shifter, or the later one with that rectangular rubber thing like the 9000's have?