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SHANE 73Z
12-06-2004, 02:32 PM
Hey guys,

I have finally decided on my first brake upgrade for my Camaro.

I will be running a Touring Classics 12" C4 style rear kit. For the front I will be upgrading my front calipers to the Dual piston D52 replacement calipers from Stainless Steel Brakes. I have already done the B-body spindle swap so that gives me 12" front rotors also. The SSBC dual piston calipers have the same bore as the C4 PBR calipers.

So essentially I will have C4 calipers all around. I have decided the brakes will be unboosted.

Now for the real question:
What are the pros/cons of using a setup like this:
http://cncbrakes.com/cncbrakes.com-asp/sra.asp?grp=sra&subgrp=d&series=240&subseries=

Versus a traditional tandem master cylinder with a proportioning valve. Which is a better setup functionally as far as ease of use etc? From a selection point of vew there are far more MC possibilities with the balance bar type arrangement. Is there any advantage to mechanically adjusting the engagement of individual masters vs the restriction of fluid to the rear brakes?

Also in light of seeing David Pozzi's update to the "Cheap Big Brakes" thread, are we running ourselves out of the OEM style master cylinder possibilities by trying to run these small bore calipers without any assist??? It seems to me that we just cant find small enough OEM MCs to run on our cars.

Thanks for the help (my brain hurts),
Shane

P.S. David if you read this, what are you running on the rear of your wifes car??? I also have a very specific question regarding what you found as far as pushrod holes on the pedal of your wifes car.

SHANE 73Z
12-08-2004, 12:40 PM
Well guys,

I talked with JMC Motorsports today. They have a kit as shown above available with the GM MC mounting pattern and they recommended 3/4" MCs for front & rear both. They say there is enough adjustment in the bias bar to sufficiently proportion front to rear.

The only thing left to determine is hardware needed to attach to the stock pedal and making a reinforcement plate for the firewall. I will be collecting & fabricating parts over the winter and installing in the spring.

Shane

David Pozzi
12-09-2004, 02:26 PM
I started with 15/16, then tried 7/8", then 13/16".
The 13/16" was fairly nice for easy stops but took a lot of pedal pressure to lock a wheel. My wife could not lock a wheel, while I could but was pushing so hard I'd not want to run an open track that way. I was considering using different pads, that might do it, but we are going back to a power booster since the engine will have good enough vaccum for one. I'll probably start with the 15/16" bore MC on the booster.

I ran across a mention on the third gen forum that the manual pedal hole on late TA Firebirds is something like 3/8" higher. That might make enough difference in conjunction with a small bore master cyl.

I plan on putting the MC part numbers on my web page when I get a chance. They will be on the second gen page.

The rear calipers on the 73 are C4 type.

David Pozzi
12-09-2004, 02:34 PM
On the subject of dual vs tandem master cyls, the tandem advantages are:
1. exact sizing of F/R bores, no wasted travel due to wrong sizing.
2. Linear adjustment of F/R proportioning

The disadvantages are:
1. More linkage and brackets.
2. Linear adjustment and reaction of the F/R line pressures MAY not be what you really need, as weight shifts forward a different F/R ratio is "ideal" (needs are not linear). An adjustable prop valve can kick in with a different line pressure curve that is more ideal.

Stop Tech has some good articles on brakes and proportioning.
http://www.stoptech.com/whitepapers/brakebiasandperformance.htm STOPTECH ARTICLE ON BRAKES

Here is one on proportioning valves vs balance bar: http://www.stoptech.com/whitepapers/proportioning_valves.htm

SHANE 73Z
12-09-2004, 04:09 PM
Thanks alot David,

That is the kind of info I was looking for. The setup that I showed above is a very simple install (I dont plan on an in-car adjuster setup) Using a Master Power power-to-manual bracket It will bolt directly to the firewall and then a rod will have to be fabricated to go to the pedal. The Setup shown has a female rod end provided.

As I said above JMC motorsports recommended 3/4" MCs for both the front & rear.

I take you were the running the manual master in the stock power brake hole on the pedal?????

I will get to reading now,

Thanks again,
Shane

SHANE 73Z
12-09-2004, 05:01 PM
David,

That was great reading. I came out with only one question.

They refer to the "knee point" of a prop valve. Does this knee point only apply to stock style prop valves??? I cant see how a "knob style" adjustable prop valve could incorporate that function???

I was under the impression that an adjustable proportioning valve merely restricted flow. If this is the case the function of a bias bar and adjustable prop valves would produce the same bias & bias curves just by a different means.

Take care,
Shane

David Pozzi
12-09-2004, 10:42 PM
The stock and the aftermarket prop valves have a spring inside, the knob screws down on the spring and adjusts the "knee point" the point where the valve kicks in.
Above the knee point, the pressure is controlled by the rate of the spring. If the spring is the correct rate, this might be a more ideal way to deal with rear lockup but who knows?

I'm not pushing either method, just pointing out that adjustable prop valves may not be so bad after all. You hear a lot about dual master cyls being ideal, but the ratio is linear and the need is not allways linear.

There are some valves like the one on my 89 IROC that are not proportioning valves, they limit rear pressure to a set value, no higher, to prevent rear lockup. I wouldn't use one of those valves.

SHANE 73Z
12-10-2004, 06:19 AM
Thanks again,

Just thinking aloud again, I think I am going to try the balance bar setup. But, if I dont like the linear proportioning, is there any reason why I couldnt adjust the balance bar back to equal F/R biasing and use an adjustable prop valve (in the rear line) to get back to get a more "stock" non-linear bias curve??????????

I have learned mucho this week!!!!!

Take care,
Shane

jcs
12-11-2004, 08:08 AM
Shane;
Unrelated to your brakes, but I noticed you a fellow Pittsburgher - I am in Bethel Park. Hope to run in to you one of these days. Once your brakes are sorted, bring the car up to BeaveRun for one of their open track days - I did it in September and had an absolute ball in my 1968 - ran my 15 year old Radial T/A's down to the cords! I'm spending the winter playing with springs, race rubber, etc. Once the new track forum is open, I'll try and get more people up to one of those events. They are really nice people up there.

Conekiller13
12-11-2004, 06:37 PM
The dual master cylinder set up gives true front to rear brake bias adjustment. When You adjust the balance bar Your giving Yourself a wide range of pressure difference. The knobe style prop valve adjusts only less from a given point. If Your master cylinder doesnt match Your caliper selection, I.E. rear calipers have more than 40% of the piston are of the front then no amount of knob twisting will work. With the same size calipers all the way around You need separate masters.

SHANE 73Z
12-13-2004, 06:53 AM
Daniel,

I was hoping you would chime in here. I understand the difference in the 2 systems and I can understand why they have different curves to the biasing. How do you like the street performance of your dual master setup. My brakes will essentially be stock C4 front & rear calipers so the bore sizes work. I asked the last question because I havent heard much feedback on the bias bar setups on the street.

Given the fact that 3/4"MCs have been recommended to me it would seem if the bias bar were adjusted for even pressure I could use a knob type proportioning valve effectively and get a less linear biasing (more similar to a stock prop valve)

What is the rest of your brake system and how do you like its street performance??? I have no doubt the bias bar setup is superior for the track, but wonder if it is overkill or even just the wrong application for the street.

Shane