Brake Booster and Master Cylinder

[jcraigau]

Hi Guys,

I'm at that point where it's time to find out all about the exciting world of braking, which I'm quite passionate about.
If it doesn't go that's a small problem, if it doesn't stop, that's a huge problem!

The "build manual" has the following one line in total "Ford master cylinder, with Sigma booster" - Handy!

So I'm open to ideas as to what others have used...

From the research I've done I need a S230mm PBR VH429 2 stud front can.
Then I found that the VH429 was replaced with VH415R.

Thanks,
JC

[stephen low]

JC

My kit already had this gear with it but the best advice I've heard is to try and use parts from utes to replicate the general weight distribution of a cobra.

Makes some sense as the ute rear has little weight in it like a cobra.

All I know is that my Ford - Sigma master-booster combination passed the braking test but my engineer was keen to see if I could engender a bit more overall braking performance.

He suggested trying to transfer some more of the braking load to the rear brakes by way of using a different crack pressure setting.

The suggestion means a switch in a set spring that modulates this pressure and I only had one option with the gear I have. I had this change done through my brake shop contact but am yet to put it to the test on the road.

If you can go with something more current try and do so and all you have to match up is the fitting arrangements to the standard pedal box, if you are running this and that can always be modified for a different attachment arrangement anyway.

A couple of photos from my photobucket account of the very thing!






Anyway good luck on the research and I'd be keen to hear more of what you decide upon.

Slo

[boxhead]

Not sure what kit you have Slowy, but mine is heavier in the bum than the front.

[Gav]

I'm with Dave on that one.
With an alloy engine the weight bias is to the rear.
Mine is 45% front and 55% rear.

[PeterAllen]

I’m open to be corrected on this… My understanding is that Ute M/Cs don’t have a built-in proportioning valve and this allows you to fit a stand-alone proportioning valve. Otherwise if you use an M/C with a valve and also fit a stand-alone valve you will have all sorts of problems.

Utes have a device fitted to the rear which will adjust the brake bias according to the ride height and thus the weight carried. Here is a photo I took of the device on the VZ SS Ute I used as my donor car. The long U-shaped rod is the sensor.

[jcraigau]

Ah, I've got one of those, as my donor was a VU SS. I was wondering what it was for!
Apparently the booster from the ute is too big, but I might measure it up to see...

[Gaz64]

Originally Posted by PeterAllen

That actuating lever is normally tied to the diff centre on Commodore.

How does it work now, and do your brakes work correctly?

[PeterAllen]

I've fitted the Holden booster. The issue I had was that the plunger rod is not held in with a circlip (bugger) but is fitted prior to the booster halves being joined. It required that I have a specialist split the booster and remove the plunger so I could shorten it and machine a thread. I then had to have a specialist refit the rod and rejoin the booster. If I recall it was only $20 + $20.





I'm not sure on the exact details but there is something about the reservoir on the M/C has to at least match the piston capacities of the brakes. I'm running Wilwoods and the Holdem M/C just makes it. Someone may need to clarify this point.

[PeterAllen]

Originally Posted by Gaz64

That actuating lever is normally tied to the diff centre on Commodore.

How does it work now, and do your brakes work correctly?

I'm not sure of the question? I'm not fitting the Ute sensor to the car, I was trying to explain that as far as I know passenger cars now have the proportioning valve in the M/C and it's probably best to fit an M/C without a valve (e.g. one from a Ute) and then install a stand-alone proportioning valve so you can easily balance the brakes to suit the weight distribution of your car.

I had removed the rear-end before I noticed the bias actuator (and took the photo) so I don't know where it contacted. I have a stand-alone Wilwood proportioning valve fitted but the car has not turned a wheel so I can't say how it works. Hope this explains a bit better.

[Outwest34au]

Hi JC,
if it helps, I was going to go the sigma route, but it was just a tad too long. It originally had an old XY-XA Girly, but ended up throwing away the oldy Girly booster the previous guy had butchered and got a XY-XA PBR brand spanker (fully reco) from Terry at Hydroboost. Awsome guy to deal with, he had it in the mail before I could pay him. The input rod was too long but I never gave him specs previous, so he sent up a correct length rod which we fitted locally.
The PBR is bolted to an XY-XA master cyl and it appears to work well with my alloy donk and jag brakes all round.

Cheers

Edit, has not been engineered for brake testing, just my observations.

[Andrew429]

Hi JC,

The G-Force standard setup is as follows (if you want to go that way):
Sigma Booster (it's one of the smaller boosters available), XD/XE Master cylinder.
You can pick up both from a wrecker and Perth Brake Parts will recon them for you.
Tell them its for a cobra and needs more flow to the back brakes.
The sandwich plate (alloy plate between booster and firewall) can be cut down a bit to help fit the assembly into you wheel arch.
You may also need to "create" an access panel in the wheel arch.

[jcraigau]

I'm still hunting down the Sigma booster to no avail.
I've seen one online but it's a little bigger (by half an inch) over the standard Sigma booster. There are two kinds with different of rod diameter and rod end length.

Does anyone know the specifics of the Sigma booster?

Two options;

53-2020:
ROD DIA- 0.389”
FROM FACE OF SHELL TO ROD END- 3.857”

53-2024:
ROD DIA- .400”
FROM FACE OF SHELL TO ROD END - 3.730”