# 4 piston disc brake info needed



## chemnick (Nov 16, 2013)

Hey Guys:
I got my 4 piston disc brakes put together and I have a couple of questions. First, when these stock brakes ('67) are assembled, is it correct that the calipers are not centered over the disc rotors (these are also new 2 piece hub and rotor assemblies)? And it appears as though I am missing some sort of a 1/4" pin or rod that keeps the pads in place that runs through one side of the caliper, through both pads and out the other side of the caliper (rod, pin, long cotter pin)? Both calipers were installed with the bleeder being positioned on the highest point. Thanks, Chemnick


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## bondobill (Oct 24, 2011)

We just replaced the factory 4 piston disc brakes on the front of my sons. 68 gto
We went with Wilwood calipers and rotors
Here's a photo of the left front off the car
Bleeder is on the high side of calipers when installed
If I remember right the rotor was somewhat centered between calipers....had the whole system apart 2 winters ago. I don't think there where any spacers or shims on our calipers to center them.

The Wilwoods we installed came with a bunch of washers for centering them










Good luck

Bill


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## chemnick (Nov 16, 2013)

Thanks, Bill for the reply! Is that just a long clevis pin that takes a cotter pin in the end or is it something that looks to be "special" in some way? Can you tell me if there was something in particular you didn't like that caused you do decide to make the change?


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## bondobill (Oct 24, 2011)

Clevis and cotter, nothing special
We did some reading on different forums about these brakes. Consensus was that the factory 4 pistons where more trouble then they be worth. Advise we got was unless you wanted to build a factory correct bone stock car, swap them out.
We looked at buying stainless sleeved factory calipers but at the price they wanted for just the calipers we could go with a aftermarket brakes system with larger rotors


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## chemnick (Nov 16, 2013)

Thanks again, Bill, for your time to respond.
Chemnick


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## BearGFR (Aug 25, 2008)

I too am running Wilwood's and have never worked with the factory 4-piston calipers (my car originally had the big single piston front calipers), but some of the Wilwood information still might apply.

Caliper location: The calipers mount so that they're almost 90 degrees away from the top, and towards the rear of the car ("pointed" at the rocker panels, if you will).

There's a long cotter pin that inserts through small holes in the top center of the caliper on both sides, and through the pads. That's the only thing holding the pads in.

Centering the caliper on the rotor. Willwood provides shims of various thicknesses (they look like washers) with the instructions to use them between the caliper itself and the mounting bracket (on the mounting bolts) as needed to center the caliper on the rotor, side to side.

Bear


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## Squidtone (Nov 26, 2010)

chemnick,
These 4 piston calipers are the Delco Morraine brakes.
Theoretically, I believe that the fixed caliper design with multiple pistons is a superior design, from a performance point of view, compared to the single piston "floating" caliper design. Just look at the performance aftermarket stuff out there...many of them are 4 or 6 piston systems with fixed calipers.
However, from a reliability perspective, they have four times as many seals, and the factory Delco Morraine calipers are cast iron. Rusty pitting over time. Of course this can be fixed by having them sleeved with stainless steel. I had this done over 20 years ago and the bores still look like new.
However, a different problem is with the lip seals.....they lose their sealing power after a couple years, particularly if they sit for long periods. If you want to keep these brakes, you will probably have to replace seals every few years. Dorman still sells inexpensive kits although the boots are not correct.
These 4 piston brakes are the very same brakes (perhaps minor difference in piston sizing) that all the Corvettes came with from the mid sixties up into the early 80's. There are thousands and thousands of these brakes systems in use. There are a couple companies dedicated to providing kits and parts for these brakes. Some of these companies offer "upgrade kits" to convert the lip seals to "O" rings. Many folks like this conversion (you need to replace the pistons too) because the seals last much much longer. However, I read that some engineers don't recommend this conversion because the "O" rings don't allow the piston to retract as much as a lip seal would. I think racers care about these details. I never looked into it for my GTO; I'll just replace the seals every few years. 
I like these brakes (my 67 came with them). They work great, and with my new one piece rotors, they're very smooth. They look good behind the rally wheels too. Yes, they're a pain in the butt. Yes, you need the rare rally wheels to fit around them. Yes, they won't be trouble free for 10 years. 
PS, I think if your caliper is slightly off center with the rotor, it's no big deal. While the caliper is fixed, the pistons float to compensate.
Good luck!


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## chemnick (Nov 16, 2013)

Squid,
I'll get the pics I took on tomorrow. I'm still kind of concerned because when everything is together, the inside pad has the inboard pistons just about collapsed all the way while the outboard pistons are out about 1/4" or so. I did not assemble these backing plates, but they look right and take the calipers just fine. At this point I believe that the only way I could get things right is to see if there is a different inner bearing and/or race. If I tried to space out the hub I'd probably lose contact between the spindle and seal.


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## chemnick (Nov 16, 2013)

An afterthought..............I believe that if I could get the hubs out that 1/4" the 14X7 Rally II's would clear......................


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## chemnick (Nov 16, 2013)

*Pics of calipers*

Here is what I've got going on........................


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## Squidtone (Nov 26, 2010)

Chemnick,
Great pics. I see your problem. I have to admit, that does look like too much of an offset.
My initial question would be about your mounting brackets. They bolt onto the spindle with gigantic grade 8 bolts. Then the caliper itself bolts to those brackets with smaller grade 8 bolts. Are your brackets original? Are they shiny new? I have seen that these are reproduced...but if you have original brackets you can rule that out.

Second thing I'd look at would be the rotor/hub...are those repro's? Could those be incorrect dimensions? If it comes down to it I can measure my car which has all the original brake parts except for rotors, but my new rotors fit perfectly and are "centered".

I see you mentioned your rally wheels making contact with the calipers...most 14 inch rally II wheels DO make contact with the 4 piston calipers...Only a select few early 14" rally II wheels will properly fit the 4 piston calipers. Two that WILL fit are 14 x 6", and they are the "JA" and "JC" wheels. There are one or two more that will fit too. But anyway, you can simply make 1/4 inch thick wheel spacers out of a good 6061 aluminum and that will solve your problem. I used spacers back in the 80's when I didn't know about the correct JA or JC code wheels and they worked fine.

Anyway, here's a shot of my caliper/rotor.....


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## chemnick (Nov 16, 2013)

Squid,
The brackets appear to be of some age, unlike the hub/rotor assemblies. A difference that may not mean much that I see is that the tapped holes which (I think) come in from the back side to attach the two pieces of the hub seem to be missing. Does this matter? O would have to take a pic from the outside for you to see. The wheels. The one wheel I have been checking the clearance with is a 14X7 which has a stamp code of JA next to the valve stem hole, might that be the one you refer to? Also, the bracket which I can see that receives the flex line is not mounted securely yet, but is loosely conneted lower on the backing late. Sounds like I need to take a closer look and take some more pics. Thanks again...............


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## Squidtone (Nov 26, 2010)

Okay, you kind of lost me on the reference to the threaded holes from behind...do you mean the hub/rotor? Do you have two piece hub/rotors? They are held together with 5 bolts (from backside of rotor)

They did make 1 piece hub/rotor assemblies (aftermarket) for a while...I have a set....

Anyway, I'm wondering if you should check to see if you have correct calipers. There were big bore units and small bore units. I think the small bore is what GTO's should have, which is a 2.0625" bore caliper.
The outer half of the caliper has a raised part number 5455946, the inside half part number should be 5456008. 

The brake hose bracket is fastened to the caliper bracket I believe...with one bolt....

Wheels, you have a JA wheel? That is a 14 x 6 wheel. That is the correct wheel to fit a 4 piston caliper GTO/LeMans?Tempest. Wheels are measured from bead flange to bead flange. The overall width is probably 7 inches, but it's still called a 6 inch width. Nice wheels and rare too. keep 'em.

See if you have the correct casting numbers on your calipers....


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## chemnick (Nov 16, 2013)

Squid:
Just sent a PM prior to checking the thread. I will get answers to your questions about the casting numbers and caliper piston size in the AM. Yes, I have a JA wheel which I did measure across from bead to bead and get 7" and I stated it as a 14X7 (stupidly) because someone had written "14X7" on the inside in magic marker. Another thought, is there a spindle which is exclusive only to 4 piston disc brakes?


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## chemnick (Nov 16, 2013)

One last answer, my reference to threaded holes was because I have seen pics of some hub/rotors (supposed to be 2 piece) where you can not see the bolt holes for the bolts that hold the two pieces together because they were not drilled through all the way until they came out between the lug studs. On the ones I have the holes ARE drilled through, thus I can see the tapped holes between each lug stud. Hope this makes it a bit clearer.


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## Squidtone (Nov 26, 2010)

The spindle is not unique for the 4 piston caliper cars. They are the same for 67-72 disc brake cars whether it's a 4 piston or 1 piston style brake system. I assume this because the catalogs list a reproduction spindle and specifically say it'll fit either style brake system from 67 to 72, including the 67-68 only 4 piston caliper cars.

Yes, I understand what you mean by the bolts being threaded through the hub. I remember my original hubs had the bolt holes threaded through; you could see the bolts that fastened the rotor to the hub from the hub side.

I'm gathering from your comments that you got this brake system included with the car but it was never up and running? Do you suspect that there are some mixed up parts?

Well, comment back when you get to check the numbers...


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## chemnick (Nov 16, 2013)

*More pics*

Here are the latest pics.


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## chemnick (Nov 16, 2013)

*Some Additional Info*

Bill:
Thanks for the numbers. They match up with what I have for measurements. However, now the situation gets worse. I was taking some pics (if I can't insert them here I'll just add a reply to the thread) when I noticed that the brake fluid connections on these things are machined for banjo bolts. I was under the impression that (judging by the new short steel lines I have) the connection was a flare connection. Is there an adapter piece that I am missing? Also, I get 1.785" for a piston diameter (1 25/32"). The casting numbers, however, are exactly what you said they should be (see pics) and the rotors have a cast number of TH12441A. I'm sure you are aware that the calipers bolt up just fine to the backing plates and the pads line up with the arc of the O D of the rotor perfectly. I'm about a stone's throw from cutting my losses and ordering a generic front disc conversion kit. In answer to another question you asked, I bought this unit as a complete rolling frame with the brake parts in a box, calipers blasted but then left loose. I took the calipers to a local rebuild shop and had them done. I guess I should have tried them before sinking some big bucks into their rebuild.


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## Squidtone (Nov 26, 2010)

Chemnik,
Man that's a drag. Sorry you're having all these silly problems. It does look like you have the right caliper castings, and the correct brackets. That leaves the question of the rotor/hubs themselves. 
And now you've got the problem with the brake line stuff. It does look like your brake line bracket is not right. The brake hose/pipe junction bracket should bolt to the caliper adapter bracket. My 67 uses one bolt for that bracket, and I found in the Zazarine GTO Resto book that the 68's had a different bracket that was held on with two bolts. If you have the Zazarine GTO resto book, it's on page 224 for the '68, and page 218 shows the '67 assembly drawing. The hose comes down to the brake hose/pipe bracket, and then a very short hard pipe connects from the hose to the caliper itself. The little short hard pipe is a regular flare type brake line. It looks like your caliper does not have the hard inverted flare for the flared brake line end?
Well, I understand you just may want to abandon trying to fit all these unknown parts together. If you do, you might have value in those parts. I searched a bit and found one guy sold just his original calipers and got 500 bucks for them. Those have value to somebody out there.
Just so you know, OPGI, AMES, PY, etc, sell alot of piece parts for these brakes. I believe they do sell the mounting brackets, (shiny zinc plating), brake hose bracket, and rotors, etc. But I see you just might want to go with a whole new bolt on system with a more common single piston caliper. Good luck on whatever you decide!
I


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## Squidtone (Nov 26, 2010)

Chemnick,
I'm still thinking about this, and I just looked at your pictures again:

Regarding your rotors, Is the thickness about 1 inch? 
It looks like your rotors are not that thick. I believe there was a version of these brakes used on some other GM cars that used thinner rotors. 

The A body rotors should be about 1 inch thick.


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## chemnick (Nov 16, 2013)

I will check on that tomorrow and get back to you..................


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## chemnick (Nov 16, 2013)

*More on brakes*

Took the wheel and hub off to get to the backing plate and dust shield. Part numbers are shown. Still getting nowhere. Maybe pics will help??:cryin::cryin:
The small brake line bracket which looks nothing like what is supposed to be on these breaks was mounted at the lower rear spindle bolt. I did find a predrilled hole for the correct bracket to be attached, however the hole has never had a bolt in it (no threads).:eek2::eek2:


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## bondobill (Oct 24, 2011)

I'll check the part #s on Brents tonight, easy enough seeing's how they are off.

Bill


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## Squidtone (Nov 26, 2010)

for what it's worth, the caliper bracket on my GTO has a big part number 
1381720RH. Obviously that's for the right hand side. 
I think you've got the correct caliper bracket and shield parts. Obviously you don't have the correct brake pipe/brake hose bracket. Odd that the hole in the bracket is not threaded for a hose/pipe bracket.
I still wonder if you've got the right rotors/thickness.
Dave


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## bondobill (Oct 24, 2011)

Found this photo from when we did the suspension couple years back, as you can see the inside pad has the calipers completely compressed while the other side did not. Ran them this way and had no issues, worked just like they were supposed to. 


Why your wheels don't clear 
Brent was running 14" rally 2 with no problems.

Heres a photo of L hand bracket for caliper, different # then yours, our dust cover has the same # as yours


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## Squidtone (Nov 26, 2010)

Bondobill,
The picture you posted of the caliper bracket looks like it could be a 1968 bracket....they used two screws to fasten the hose bracket to the caliper bracket. 67's used one screw. There is an excellent picture of the 1968 parts in the Zazarine book on page 223.


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## chemnick (Nov 16, 2013)

Squid:
I know you had asked about the rotor thickness before. Just measured one (with a caliper) I get 1.012" and they have "0" wear. Now I am rather curious about the difference in part numbers between mine and the picture of the ones that are 54687612L. My '67 originally had manual drum brakes which I converted to power. I guess this is getting kind of pout of hand, so if I get to then point where the frame has to go back with no solution, I'll put the drums on to get by and if I stay with them I'll sell the disc stuff.


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## bondobill (Oct 24, 2011)

Did you change the spindles when you went from drum to disc.


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## chemnick (Nov 16, 2013)

Bill:
Sorry, on this thread I did not go as far back as maybe I should have. About the time I was just going to start on the frame, I scored a frame that was already done for a very fair price. The disc setup (without the calipers rebuilt or installed) were in a box. I took over from there. I still have not gotten disc MC booster, etc. If I'm going to bail, now might be a good time................................


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## chemnick (Nov 16, 2013)

*Still have one question.............*

With regards to the calipers and their plumbing, I'd still like to know if there is some sort of adapter that threads way down into the hole where the line hooks to it that adapts the connection to a flare connection. These small jumper lines will thread all the way down until they run out of thread and never hit anything. Also, the area around the top of the hole is machined flat and appears exactly like any caliper I have ever seen that uses a banjo bolt and double copper washers. Could there be an alternate flex hose that has a banjo bolt connection? Were the Corvette calipers made to take a banjo bolt perhaps?
Thanks, Chemnick


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## motovideo (Dec 18, 2021)

chemnick said:


> *Pics of calipers*
> 
> Here is what I've got going on........................


I am going to revive this thread as I have the same thing going on as chemnick when trying to install replacement calipers on my 1968 GTO, and was unable to find any data about why the caliper had a very tight fit, and caliper was not centered over the rotor properly. Although these appear identical as the outer castings have the same part number, there are two inner castings - 5455008, and 5456008. The hole depth on 5455008 is 1.034" , and the hole depth on 54556008 is 0.956". I did not compare the piston sizes. Summit is selling Cardone replacements as a correct fit as I write this, and it's not accurate. I hope this saves others some trouble!


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