New (Positive) Findings with My Braking Woes...Please advise

[BanditDave]

Hey Guys,

I have been on several sites complaining about my brake issues with my Pro-Touring '78 TA and I think I am finally on the right track. Here's the details:

Bled the living snot out of the brakes...many many times. Could not get a rock solid pedal with the brake booster vacuum line attached. It is a DSE Booster/Master combo with all new lines, adjustable proportioning valve and basically stock '99 TA rear calipers mounted up front and '86 Grand National front calipers mounted on the rear (no e-brake at this time). I did the 1LE upgrade to the front with Impala spindles and 12" rotors. Stock size rotors in the rear.

I decided that I would get saucy and drive the thing up and down the driveway and see if I can stop the car...I have enough runoff to not cause any damage to anyone but the car...haha

Anyway, the pedal feel is really crappy as well as travel but the brakes grab REALLY well. I believe that the fuel tank was a little low but the motor actually bogged on a couple of the stops (different issue but easily fixed). I am beginning to believe that the master cylinder might be too large for my relatively small brake set-up?

Any and all ideas are appreciated!

I am going to start a build thread on here soon.

Thanks!
Dave

[Apogee]

... It is a DSE Booster/Master combo with all new lines, adjustable proportioning valve and basically stock '99 TA rear calipers mounted up front and '86 Grand National front calipers mounted on the rear (no e-brake at this time). I did the 1LE upgrade to the front with Impala spindles and 12" rotors. Stock size rotors in the rear...

Could you please clarify your setup again?...are you really running '99 TA (presumably TransAm?) rear calipers up front which have a 45mm [1.77"] piston diameter and '86 GN front calipers which have a 63.5mm [2.5"] piston diameter in the rear on 12"x1.1" GMF3 1LE F-body rotors and 11-3/16"x1" 2nd gen F-body rotors in the rear?

Not to make light of your situation, but if that's the case then I think you've found your problem already. Your brake bias is basically opposite of what it should be front to back and adjustable proportioning valves are only meant to help fine tune and adjust what should essentially be a well designed and thought out combination of components.

The master cylinder/booster combination would be fine if your calipers were reversed front to back...is that something you've considered? You could run the OE 12" B-body brakes with the wide-body 9C1 calipers (or any of the GMIII off-the-shelf replacement options to shed weight) up front and then put the LS1 rear brakes out back where they belong.

What are your goals for this thing and what is your reasoning for heading down the path you have already started down?

Tobin
KORE3

[critter]

Listen to Torbin. The brake bias is all wrong.

[Ishmael]

I think he's just written them the around way wrong. If that's the case then maybe he just does have the wrong sized master. Is it by any chance a "70s corvette style" master?

[Apogee]

I think he's just written them the around way wrong....

I thought that too, but Dave specifically stated that he was running front calipers in the rear w/o a parking brake. I've still got my fingers crossed though that they're switched because that would seem to be a much better system in the end.

Tobin
KORE3

[David Pozzi]

I think he's saying he has 1LE front calipers up front and 2.5" bore on the rear.
What's the bore size of the 1LE front calipers?

I agree, the rear callipers are too large compared to the front.
David

[Apogee]

David, I thought that at first too, but I think he's just running the 12" 1LE rotors on the B-body spindles since they're the same as the 91-96 B-body rotors except that they have the 5x4.75 pattern. The 1.1" thickness could be made to work with the rear LS1 calipers if the pads were slightly worn...I'm not sure whether new pads would fit since they're designed for a 1.02" rotor thickness.

The 1LE calipers are just C4 front calipers, which have twin-38mm [1.5"] pistons with an area of ~3.53 square inches, or a single-piston equivalent piston diameter of 2.12".

It would be nice to know some of the back story on this thing.

Tobin
KORE3

[BanditDave]

Hey Guys,

I will be honest with you...I went off of what a gentleman, who will be nameless at this point, told me about a set-up he used. I wanted to keep the set up budget friendy because I don't have the huge dough a lot of guys on here are spending on their cars.

Tobin, you are correct in your first assumption. I used '99 rear F-body calipers up front. They fit very well with brand new pads. They are on B body spindles and 12" 1LE rotors.

On the rear I am using '86 GN front calipers bolted to stock '79 F body rotors.

I was told that this set-up would work, but I never investigated further on bore sizes because I was told it worked well. Stupid me, I trusted that the person actually new what they were talking about.

Judging by your responses, I need to get the right calipers set-up on this thing because my bias is all messed up.

Because I have to ask the question...and am NOT really going to do thi...if I switched up the lines out fo the master, would I probably get better pedal feel?

Also, Tobin, what would you recommend for a brake set-up knowing my spindles and rotor size?

This car is going to have some spirited driving and possibly some laps at Thunderbolt Raceway in Millville, NJ.

Thanks guys for not laughing at me too hard...

Dave

[Ishmael]

Nobody was laughing. There's got to be a reason for what you did. I think brakes are too serious to laugh at. I only read this forum to try to learn so what you did is something I would have done had I been told to. The good thing is that Tobin seems to read every post on this forum and he is an expert. You're in good hands.

[BanditDave]

No worries, I am definitely open to a high performance alternative to stock calipers but if that is what will work, I could always nab SSBC twin pistons for the front and stockers in the rear.

Thanks guys!
Dave

[BonzoHansen]

Are the front spindles modified at all? Can you still install stock calipers? Or are the mounting ears gone?

[BanditDave]

BH,

You can most definitely install stocker fronts there. I am going to probably go with SSBC stock mount dual pistons upgrade rotors. it is a nice upgrade since the spindle moves the caliper out 1/2"...allows for a 1 inch larger rotor.

Dave

[critter]

No one's laughing. I knew what it was because I had made a similar mistake. That's how we learn.

My situation was that I had done the 1LE/Bbody upgrade on the front of 74TA but used Howe dual piston calipers with the largest diameter pistons they offered. After all, if some is good then more is better, right? ;) On the back I had installed the WS6/Cadillac calipers with the built in e-brake. I never did get a firm pedal. Then some brake experts showed me the math and how it wouldn't work based on the MC I had. When I swapped the Howe's for a stock caliper I immediately had a firm pedal and the best braking ability I've ever had on this pig of a car.

[Apogee]

BH,

You can most definitely install stocker fronts there. I am going to probably go with SSBC stock mount dual pistons upgrade rotors. it is a nice upgrade since the spindle moves the caliper out 1/2"...allows for a 1 inch larger rotor.

Dave

Whew! That's a relief. I was mostly just concerned you were going to spend more time and money trying to get a sub-par system up to par...or even bogey at best, and still be dissapointed in the performance at the end of it all.

Since you've still got the OE caliper mounting ears on the B-body spindles, I would personally run the Caprice 9C1 police caliper and thick pads (something along the lines of a Hawk HP+ with a "GG" coefficient of friction). This with the current rear disc brake kit you've got should give you a much better balance front to rear and reuse a some of what you've already got with the least amount of rework and/or effort.

If you really want to run SSBC twin-piston calipers up front, keep in mind that you'll have a lot less piston area with that caliper than with the single piston cast iron 9C1 units. Even with the increase in rotor diameter, you'll still be looking at a reduction in brake torque. I probably wouldn't go that direction, but if you do, I would recommend moving the LS1 rear calipers you have on the front to the rear. The rear calipers' 45mm pistons would balance out with the twin-43mm pistons of the SSBC similar to a 98-02 F-body. On the plus side, your MC/booster combo should work really well with the above combination. The B-body front and G-body fronts in the rear will likely require a larger bore MC or a stepped bore, quick take-up unit as I believe those G-body calipers will have the low drag seals in them and retract the pistons further than both the older and newer designs.

Rubber side down,
Tobin
KORE3

[BanditDave]

Tobin,

Thanks so much for the help...love this place.

Let me pick your melon for a little longer. Could I move the LS1 Calipers to the rear and go with the Caprice calipers (thick pad) in the front (knowing that I may have to get another Passenger caliper in the rear to properly match the staggered shock set-up)?

Thanks!
Dave

[Apogee]

You absolutely could move the LS1 brakes to the rear so long as you take the staggered shocks into consideration and either stagger your calipers to match or inboard your shocks. The 9C1 calipers and pads or even the standard B-body setup up front should at least get you back into the proper ballpark with respect to balance front to back, maybe a little heavy towards the front, but that's at least workable. FYI, the factory B-body setup has a 2.94" [74.7mm] front, single-piston caliper and 2.13" [54mm] rear, single-piston caliper.

What I like about moving the LS1's to the rear is that if/when you decide to upgrade to big-brakes up front, they'll balance out well with any C5/C6 based front kit as well as numerous other aftermarket setups.

Tobin
KORE3

[BanditDave]

Alright man...you convinced me...

LS1s in the rear, SSBCs up front...

You drive a hard bargain!

Just to be annoying, could I possibly find an off the shelf caliper similar to the SSBCs that would work in my application? It has been a LOOOONG frustrating road with this thing and frankly I want to get it done this weekend!Of course I will wait if it means doing it correctly.

Thanks a lot guys!
Dave

[Apogee]

Other than race type calipers like the Wilwood GMIII and Howe 2-piston aluminum unit, not a lot jumps to mind as for as bolt-in caliper options go. Maybe somebody else will think of something else...I'm drawing a blank on any more.

Tobin
KORE3

[jackfrost]

You could run the OE 12" B-body brakes with the wide-body 9C1 calipers (or any of the GMIII off-the-shelf replacement options to shed weight) up front and then put the LS1 rear brakes out back where they belong.

I have Wilwood GMIII calipers on my b-body spindle swap, and they are very nice (and light) pieces.

http://store.revolutionbrake.com/wil...i-caliper.html

[BonzoHansen]

On my 77 Z I'm using b-body spindles, the 3rd gen 1LE rotors, hawk pads for a 96 Impala SS and the stock 77 Camaro calipers.