Clutch master you use with G50?

[Frank818]

Hey guys,

I'm from the 818 forum, fitting a VR6 turbo in and using a G50/01 trans.

I know many of you are using a G50 (/52 probably) with your big V8 powa. I have come to the severe conclusion, after the car ready for go kart, that the Impreza master is not strong enough to disengage the G50's fork (with a KEP heavy duty clutch). I need to change my master and apply whatever modifications at this far stage of the build to get something working.

I know a Tilton master and the Porsche 1987-1989 ones will work.
But what do you use? C05's master? Something else?

By any chance, do you have physical specs of your master?
The Subaru has 2xM7 or M8 holes about 2-3/4" apart.

Tnx

[kabacj]

hey Frank. We use will wood master cylinders and pedals on the GTM.

You will need to play with the master cylinder bore pedal travel and slave cylinder travel.


The key is to be sure not to over flex the clutch diagram springs.

Anything can be done, I suggest trying some of the willood master cylinders. I'm sure you can find a master / slave setup that will work.



John

[Frank818]

Hi John,

Tnx for that, will help me get the ball rolling on this.

So it's a 7/8 bore, slightly bigger than OEM 19mm, good to know, I didn't know which bore to get, OEM, smaller, bigger...
Now I need to see what stroke I need.
I guess keeping my OEM C4 (Porsche) slave should be ok. I need a more powerful master to go along with that.

Nice picture you got there, what's funny is that I can't find that master on Wilwood's page. http://www.wilwood.com/MasterCylinde...erLanding.aspx
Am I missing something?

A master for brakes and clutch it's the same thing or one for clutch will never work with brakes and vice versa?

[kabacj]

I went with the bigger bore on my race car to shorten the pedal throw.

The 7/8 is an odd bore I think I got it from summit or Jegs.

Master cylinders are the same used for brakes or clutch slave cylinder. The key point you are trying to figure out is the ratio of leverage travel pressure at the master and the ratio of travel at the slave.

Probably going to take some experimenting. The stock GTM setup uses 3/4 bore if I remember correctly. That works as well and offers less effort to depress the clutch but longer travel.

I'm not familiar with the subie hardware, but swapping in willwood kit might eliminate some variables. That said, if you are determined anything can be made to work.

[Frank818]

Ok I get it. I'll aim for 3/4" as my 818 is a street car and wouldn't want a too tough pedal. If it ain't working I'll move up in bore, another 100 bucks but I'll know what to do. We don't count money on these builds.

I'm pretty much fixed in terms of pedal travel, only adjustment is the clevis on the master pushrod. I guess with a proper 3/4" master it would work. The OEM subie one is 11/16 and that's about what I'm missing! I can engage slightly the gears but not fully, it's grinding very very little and car wants to move, so it's missing not much! I guess that's my problem.

I have no Subaru parts other than the master (which I need to change for non-subie) and pedal box. The engine, trans and slave are non-subie. And add the master now.

Anything can be made to work, yes it's a kit car. Except a Subie master with a C4 slave on a G50, that cannot be made to work.

Well tnx John, thank God you're there, I'll figure out what to do from here, I think the rest is just getting the right master and adjusting it.

I'll try to check at Summit/Jegs for yours so that I can find the stroke and measure mine, I already use all of the stroke by bottoming out the piston.

[The Stig]

I went with the bigger bore on my race car to shorten the pedal throw.

The 7/8 is an odd bore I think I got it from summit or Jegs.

Master cylinders are the same used for brakes or clutch slave cylinder. The key point you are trying to figure out is the ratio of leverage travel pressure at the master and the ratio of travel at the slave.

Probably going to take some experimenting. The stock GTM setup uses 3/4 bore if I remember correctly. That works as well and offers less effort to depress the clutch but longer travel.

I'm not familiar with the subie hardware, but swapping in willwood kit might eliminate some variables. That said, if you are determined anything can be made to work.

Ditto! I switched to 7/8" bore in order to "shorten" the throw due to the clutch travel issue. It was a way to keep the throw "shortened" enough to keep from breaking the stops on the transaxle housing. I also have the adjustable stop on the floor in order to limit the travel of the clutch pedal. It also gives a softer pedal for the clutch,which for me allows a better feel for the clutch and gear engagement.

My car will not be a track car. But I still want a comfortable feel in the clutch in gear selection whether the drive is easy or very spirited.

Mike

[Frank818]

Hang on, the American Stig. loll You saying the 7/8" bore feels comfy enough for street driving?

Mind telling me more on that "adjustable stop on the floor"? If there exists some kind of stop for brake/clutch pedals maybe I could fit it on my 818 too. I fabed a stop welding couple of flat bars scrap metal, it ain't pretty at all.

[The Stig]

Hang on, the American Stig. loll You saying the 7/8" bore feels comfy enough for street driving?

Mind telling me more on that "adjustable stop on the floor"? If there exists some kind of stop for brake/clutch pedals maybe I could fit it on my 818 too. I fabbed a stop welding couple of flat bars scrap metal, it ain't pretty at all.

It's like a hood "bumper" that would screw up or down for adjustment. It keeps the pedal from going all the way to the floor, and potentially over-stressing the transaxle.

It's pretty simple. You just need to find the point on the floor or in the frame, where this can be mounted. Then you need to find the point in the clutch throw where it's depressed enough to disengage the clutch, in order to know where to set the stop.

The 7/8" slave allowed a lighter pedal/feel in my oppinion. The 5/8" (I think it was), felt pretty tight and took a bit more effort to push in, and hold.

Mike

[Cattrax]

Smaller master cylinder = less pedal effort but longer travel needed to release clutch. Also different pedal assemblies have different leverage ratios. You can measure yours. It is simply a ratio of lengths from the pivot point. Pedal to pivot vs cylinder pushrod to pivot. Wilwood assemblies for the GTM are 6:1 if I recall correctly.
Ken

[The Stig]

I know that the feel/pressure of my pedals feel much more comfortable since I've switched the pedal assembly, and the master cylinders (brake and clutch).

Mike

[Frank818]

Well tnx guys, I now know the small subie master is 11/16 bore and 1.125 stroke. If I keep same stroke and increase bore, that should work. Less variables I play with the better.

I have measured physical sizes and just need to find either Wilwood or Tilton whichever will physically fit best.