500psi T-Bird Calipers

[Broncobowsher]

I've lost track of how easily the calipers bleed. If not easy, then I can see maybe there's a problem internally where something is acting to reduce the pressure at the bleed screw(s). Would be a supercalafragilistically weird thing to happen, but weirder has happened. Only thing that could be weirder would be if the pads have become compressible somehow.

But, yeah. The flex hoses are usually the culprit for weirdness in a brake system.

I am thinking this is a new build, and maybe the pads are a bad batch. Maybe from a shady supplier. I've heard of some counterfeit pads being found to be little more than compressed cardboard. I was not considering the pads to have started as good and gone to bad.

 

[chuzie]

Any benefit to 7/16 vs 3/8 fitting? 7/16 has to be adapted anyhow so, with my 77, I may as well remake the hard lines to 3/8, no? ID is the same.

 

[ba123]

the fewer points of failure, the better, that's why I redid mine instead of adapters.

 

[chuzie]

the fewer points of failure, the better, that's why I redid mine instead of adapters.

My thoughts exactly!

Be sure to buy the hose and the fittings from the same mfg. as particularly with the cover hose there can be a mis-match that makes it not go together correctly.

Hold up, you're making brake hoses without a crimping setup!? What is this magic of which you speak? Please enlighten me as I'd love to jump on board. Details!

I've used the twist on stuff for steering lines, but brakes!?

 

[ksagis]

Just like in the picture. Rested on top rotor with wood in caliper.

Confirming you and @Apogee are saying the same thing since I think you might not be. I'm familiar with the Caddy rear brakes that get a lot of bad raps from people for various reasons, some warranted, some not so much. Is this what you did?

 

[chuzie]

Confirming you and @Apogee are saying the same thing since I think you might not be. I'm familiar with the Caddy rear brakes that get a lot of bad raps from people for various reasons, some warranted, some not so much. Is this what you did?

View attachment 937252

Nope. That's how mine typically rest on the knuckle with my crazy caster. I took one off and rotated it 90 degrees clockwise to what's showing in your picture with the bleeder to the sky. Didn't make a lick of difference and looking at the picture of a clean caliper instead of one covered in mud, I understand why that effort was pointless.

 

[ntsqd]

The fittings for teflon lined hose are a little different from the HO69 type fittings that PS system hoses use. The teflon hose ends require that you spread open the SS braid and insert a brass "berry" over the teflon tube and under the braid. They're a one-time use part, but spares can be bought. There's a tool made for opening up the braid. I use the time-honored traditional method that results in little punctures on my finger tips.
This gives some idea of how to assemble these hoses: https://assets.danfoss.com/documents/latest/255607/AN451068216691en-000101.pdf
Generically the fittings look like these: https://www.summitracing.com/parts/aer-fbm1100
The braid-spreading tool looks like this: https://www.summitracing.com/parts/rus-651970
Hose and fittings assembled correctly are rated for 3ksi max service pressure.

IME Caddy calipers deserve every bad thing ever said about them, and more.

[EDIT]Tool link fixed, thanx!

 

[Oldtimer]

Link to braid-spreading tool was corrupted.

Russell Performance 651970 Russell Hose Assembly Tools | Summit Racing

Free Shipping - Russell Hose Assembly Tools with qualifying orders of $109. Shop Hose Assembly Tools at Summit Racing.

www.summitracing.com

 

[Apogee]

Any benefit to 7/16 vs 3/8 fitting? 7/16 has to be adapted anyhow so, with my 77, I may as well remake the hard lines to 3/8, no? ID is the same.

No significant benefit either way. The larger tube nuts use a larger wrench size, so they can sometimes be easier to loosen/tighten, but otherwise the flow path will be defined by the inside diameter of the tube and whatever the most restrictive components are in the system.

 

[Broncobowsher]

The different size nuts were an assembly line aid. The correct line will only go into the correct hole.

 

[ba123]

Here’s a pic of my Tbird calipers mounted on my stock ‘76 brackets.

 

[snipes243]

My thoughts exactly!

Hold up, you're making brake hoses without a crimping setup!? What is this magic of which you speak? Please enlighten me as I'd love to jump on board. Details!

I've used the twist on stuff for steering lines, but brakes!?

I do this with AN style fittings. Never had any issues

 

[chuzie]

I've been pondering the issue as I await arrival of calipers and hoses. Is it possible the banjo bolts are wrong? Defective banjo fittings?

During the flow testing, I raised an eyebrow at how small the hole (fluid supply, not bolt hole) in the banjo fitting appeared to be. Does anyone have any data for something like this?

I do seem to recall having to drill these banjo fittings to a large size all those years ago.

 

[ksagis]

I've been pondering the issue as I await arrival of calipers and hoses. Is it possible the banjo bolts are wrong? Defective banjo fittings?

During the flow testing, I raised an eyebrow at how small the hole (fluid supply, not bolt hole) in the banjo fitting appeared to be. Does anyone have any data for something like this?

I do seem to recall having to drill these banjo fittings to a large size all those years ago.

Seems to me an orifice would restrict the flow and could result in a delay getting to pressure if choked across the orifice, but would not reduce the pressure if you hold the brake pedal for any length of time. Is it possible that someplace along the hardline is partially crimped and reducing flow? Base case, I don't think this could produce the symptoms of reduced pressure along the system. Seems like the lines like @nvrstuk suggested as leading candidate is most likely.

Can't remember in the thread if you visually watched the lines for growth when pressing up?

I historically get a lot more flow out of front when gravity bleeding which I always attributed to line losses on the longer runs to back versus a restriction in banjo or someplace else.

 

[chuzie]

Can't remember in the thread if you visually watched the lines for growth when pressing up?

One man band, so no. Expansion is my current theory at this point though.

 

[ba123]

These are the banjos I’m using. Pretty sure the hole does not have to be very large. It’s not like the inside diameter of the brake lines are very large.
https://www.summitracing.com/parts/RUS-640670

 

[ntsqd]

The T-Bird caliper pistons are what, Ø3-1/16"?
Assuming so, that means that they need less than 0.5 cubic inch of fluid for both to go from normally retracted to fully engaged with the disc. This isn't a fuel supply system and it's easy to get to thinking that way.
[EDIT] Assuming a Ø1.25" bore the m/c piston needs to travel about .40" to create this volume.

Stupid question, but one that I don't recall seeing discussed. Absolutely certain that the proportioning valve is in the rear brake circuit? With all of the front port/rear port confusion I can see it being mixed up fairly easily.

 

[79INA69]

I've been pondering the issue as I await arrival of calipers and hoses. Is it possible the banjo bolts are wrong? Defective banjo fittings?

During the flow testing, I raised an eyebrow at how small the hole (fluid supply, not bolt hole) in the banjo fitting appeared to be. Does anyone have any data for something like this?

I do seem to recall having to drill these banjo fittings to a large size all those years ago.

Just seeing this thread now as well. The incorrect banjo bolt can make for problems. Some banjo bolts have a groove in the center to allow the fluid to flow around the outlet, some don't. Some cheap Dorman bolts can get the hole blocked by the gasket if it's too thick. I think it could be possible that the banjo bolt could restrict the flow and pressure. One way to be sure would be to do what you said and hook the gauge up to the banjo line. You would need to make an adapter to test the banjo bolt outside of the caliper. If you have 2500 psi right where the caliper is then it is the banjo or somehow the caliper.

 

[chuzie]

Absolutely certain that the proportioning valve is in the rear brake circuit?

Absolutely positive.

The incorrect banjo bolt can make for problems. Some banjo bolts have a groove in the center to allow the fluid to flow around the outlet, some don't.

Both banjo and banjo bolt have a groove and the bolt hole falls in the center of the assembly so I don't think it is getting blocked.

Fedex arrives tomorrow with Duffs kit.

 

[Broncobowsher]

I'm starting to think the DIY braided lines are the issue.