foney_email

I remember hearing that this cannot be done if I have rear pbr brakes. Why is this? I am refering to the modification to the proportion valve to allow more pressure to the rear brakes, so they will work better, or at all in some cases.

I am getting the pbr setup, will this make my rear brakes work so that I do not need the mod, or should I still do it?

AFrikanGoodTime

With a car that comes stock with PBR brakes, you don't need to do this. From everything I've read, I have never heard of the brake system that came stock with the PBR's to ever have weak preasure in the rears.

If you are adding PBR brakes to a car that did not originally have them, the proportioning valve is most likely different than the one originally used for the stock PBR system. My best suggestion is to install the PBR brakes and see what you have before performing the proportioning valve mod. If the fronts will lock and the backs won't, (or it takes excessive pressure to lock the rears as opposed to the fronts) then perform the mod.

Maybe someone can chime in on what parts are different( and part #'s) between the Iron caliper system and the PBR system.

Ex: 1) Are the Master Cylinders the same?
2) Are the proportioning valves the same?
3) Are the hard lines the same diameter?

foney_email

So, when are the rears supposed to lock up?

I have seen other cars where the rears lock up completely when the brakes are applied and the fronts do not. An example is the jaguar in "Memento".

I have heard that the master cylinder from the drum brakes is better to have because it has a larger rear resivour (I can't spell) so it puts more pressure to the rears. Is that the best to have for my disc rear?

AFrikanGoodTime

Ideally, all four wheels should lock at the same time. If a car is notorius for push in a corner (thats where you turn the wheel but the car doesn't want to turn) which third gens are, then I personally perfer the rears to slightly lock before the fronts. This allow for better control of trailbraking when setting the *** end of the car into the corner.

I'm assuming "Memento" is a movie. Cars used in movies alot of times have tractor brakes installed on them so the stunt men can pitch the car to either side at will, just like stadium off road trucks do. This will allow a driver to lock up each rear individually or both rears at the same time. Its very much like a fancy e-brake.

I have the original drum brake master cylider and propotioning valve in my car but with non-PBR brake calipers. I don't see why there would be any difference in adding PBR calipers on all four corners. The pressure bais would still be the same front to rear. With that said, I still feel your best bet is to put them in, see what you have, and if you at that time are lacking rear pressure, then perform the proportioning valve mod.

foney_email

well, thanks man.

Oh yeah, memento is a movie where the guy has no short term memory. He has to tatoo him self with vital information so he can "remember" it. It is a truely great movie. I suggest it.

Eightyninef

89 + had OE PBR's

ANDYZ28

If you are going to perform this PBR brake installation on an '82? Then you will need to know that starting in early '84 all of the brake lines were changed to the then new ISO Metri "Bubble Flare". I encountered this problem when I did the 1LE front brake upgrade on my '82 Z28.

To make a long story very short. I would have been better off to find a '90-'92 doner car, and carefully remove all of the brake system hydraulics. Master cyl, proportioning valve, and all of the hardlines. It sure would have made life easier.

Thanx,ANDYZ28

foney_email

The kit I am getting has all of the brake lines on it. New steel and braided too.

ANDYZ28

OK, But I was referring to the brake lines that go into the Master Clyinder and Proportioning valve. You will need to replace your existing proportioning valve.

There "was" a sticky post on here at one time by me. That explained all of this master cylinder and propotioning valve stuff. But I see it is gone now.

Thanx,ANDYZ28

foney_email

Although I am sure you are right, I am stubborn, and am going to try it whenever the parts get here.

I will see what I can do.

By the way, what is this "bubble flare" what does it look like?

Is there a flaring tool to make this type of flare?

ANDYZ28

Suit yourself.

The ISO Metric "Bubble Flare" is such a pain to create, even with the correct tools. We don't even attempt it in our shop, and we have the tool.

The tool is available from SnapOn @ $around $100.00.

Here is an image from my CD that clearly shows the difference between the old style inverted flare, and the current ISO Metric Bubble Flare.

FIRECHICKEN

iTrader: (3)

Ok. So what do ya do if you have the PBR rear calipers and can't lock the fronts or the rears???? HUH

AFrikanGoodTime

That sounds scary. Its time for a complete inspection of components. It could be any number of things or most likely a combination of things. I would have to see the condition of things in person to tell you further as for trying to pinpoint one thing.

Old fluid, bad master cylinder, bad or leaky wheel cylinders, worn rotors beyond the point of turning, etc, etc,....

BretD 88GTA

I wouldn't be so concerned about whether or not the brakes lock up. The main concern should be how well the car stops. You want to be able to stop quickly and in a controlled fashion.

A lot of you guys want to lock up the brakes, but keep in mind, locking up the brakes can also mean loss of control. Once the brakes lock up, your car is headed in the last direction is was pointing. You will have ZERO steering input with the wheels locked up.

That's why newer cars now have ABS — so the average driver can't lock the wheels in a panic stop.

If the car stops poorly, I'm with AFrikanGoodTime, you need to check out the system and service it.

foney_email

I have a navy air craft hydralics guy that is working on my car...

He is the one who sold me the rearend, and he said there is no problem hooking it up to the lines. I trust that his 10 years of hydralic shop experience will get me brakes.

Please excuse my spelling errors...

Oh yeah, I am not trying to be rude, if that is how I come off, Thank you for your help, andyz28. That picture is very helpful for me to know what you are talking about.

If I need any help on it, you will be the first one I message..
Thanks again

FIRECHICKEN

iTrader: (3)

The brakes have always had little stopping power. I have always used the same pads though, Raybestos premium pads. Different rotors, rebuilt calipers. Everything else is original I think or at least the 60,000 miles of 158,000 I've owned it. So what do ya think? UPGRADE Everything????!!!! $$$$$$$$

foney_email

You can find some good deals on pbr's at the scrapyards firechicken. Just look around

FIRECHICKEN

iTrader: (3)

I have the PBR rears that came on the 89's. Is there a front set that I can get? What other calipers will fit? Anything from like an S series truck??