Questions on brake lines

[BUDFIVE]

I’m laying out how I want to run my brake lines. I have 2 questions (for now).
I’m using 316L 3/16 stainless tubing terminated with Earls stainless 3AN female tube nuts + tube sleeves,
Transitions are connected with male Earls stainless 3AN bulkhead T fittings and bulkhead straight and 90 deg fittings on brackets.

Rear brake line routing-
I don’t like the options I’ve seen for routing the rear brake line from the master cylinder to the 4” frame tube toward the rear—in front of and outside driver foot box (too close to header) or in front of and inside driver foot box(crowded in corner behind accelerator). I don’t like the idea of routing fluids through the interior but I don’t see much choice.

Question 1-What if I route as shown with the rope in these pictures? What else gets mounted to the 2x2 above the knees?
MC to 2x2 above right knee
194244

Accross to Left knee
194245

Down and through floor then accross to 4” tube and back to T at left rear.(not in picture)
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Right Rear brake fitting—
This pic has my right rear brake fitting where the soft line down to the banjo will go.
Question 2-What is the big bracket with 3 holes on the rear frame? Will I regret putting a bracket and line here?
194247

[bil1024]

Honestly, I never had an issue routing them as per the manual, in all my builds. You want them visible in case there is ever a need to replace one.

[rthomas98]

Main issue I see is where you cross it over by the drivers left knee. Most (including myself) place the fuse box there. I ran mine down the front of the foot box and I just wrapped my headers.

[JohnK]

I don't see how your proposed routing is better than just running straight down the inside corner of the footbox behind he accelerator. Your routing is far more convoluted and possibly in the way of the fuse panel.

[BUDFIVE]

Ok, seems I may be making it too complicated. I’ll look again in the morning. I see in the build video on wiring the fuse box and harness pieces go there-bad idea.

[Mike.Bray]

I don't see how your proposed routing is better than just running straight down the inside corner of the footbox behind he accelerator. Your routing is far more convoluted and possibly in the way of the fuse panel.

What I was going to say. Why make three lefts when you can just turn right? When in doubt always use the KISS method.

https://www.imagecoast.com/images/MichaelBray1/20220623151832mediumrotated.jpg

One note, since you're planning on using all stainless steel fittings be sure and use a little antiseize on the threads. But be careful and don't get any between the fitting and the tube.

[scrubs]

Honestly, I never had an issue routing them as per the manual, in all my builds. You want them visible in case there is ever a need to replace one.

I have an n = 1, but no issues either thus far with stop and go and highway drives in TN.

[John Ibele]

A plus whatever on JohnK's comments. It's really a pretty clean approach. I have one length of tubing from the MC, down the footbox behind the accelerator, and partway down the 4" frame. So only the minimum single connection inside the footbox.

Having the front panel off the footbox makes this not only possible but fairly easy. If you think ahead you can put a grommet on the tubing before you flare both ends, then put a 1/2 circle notch in the bottom panel and in the front panel, and capture the grommet in the notches when you put the front panel on. Finally, if you run the brake line to the rear on the top 1/2 of the 4" frame, tucked in between the frame and the bottom of the cockpit floor aluminum, it's very well protected.

https://live.staticflickr.com/65535/50176687028_15de838e02_b.jpg (https://flic.kr/p/2jrWCVA)
P8010008 (https://flic.kr/p/2jrWCVA) by John Ibele (https://www.flickr.com/photos/familycobra/), on Flickr

[OB6]

Nothing at all wrong with the standard routing, but my gas pedal install somewhat forced me to take a different approach. I chose to go out the front of the footbox, down the 3/4" tube and then take a U-turn to go along the 4" tube to the rear. See post 37 of my build thread.

[BUDFIVE]

Thanks guys-lots of good ideas (grommet trapped between 1/2 circle cuts, anti seize, etc). I looked again today-I’ll probably run it down the front of the footbox, probably inside.

[JohnK]

FWIW - here's how I routed mine. I used some rubber hose to cover most of the line running down the inside of the footbox to make sure there were no rattles. I ran the rubber hose just past the hole in the floor of the footbox to seal the hole. Tucked into the corner of the footbox like this, it's not in the way of anything. Later on, the entire cockpit was sprayed with Lizard Skin heat and sound insulation, and that line completely disappeared.

https://thefactoryfiveforum.com/attachment.php?attachmentid=134208&d=1598303643

https://thefactoryfiveforum.com/attachment.php?attachmentid=134207&d=1598303627

https://thefactoryfiveforum.com/attachment.php?attachmentid=134206&d=1598303612

https://thefactoryfiveforum.com/attachment.php?attachmentid=148366&d=1621826281

[Mike.Bray]

FWIW if you're going to spend the time and expense for stainless steel tubing and AN fittings use bulkhead fittings for all passthroughs.

[JohnK]

On critical lines like brake lines my primary concern is making the system as reliable as possible. One factor in this is the number of potential failure points. A bulkhead fitting introduces two additional failure points. My choice would be to make a brake line continuous and without bulkhead fittings wherever possible.

[Mike.Bray]

On critical lines like brake lines my primary concern is making the system as reliable as possible. One factor in this is the number of potential failure points. A bulkhead fitting introduces two additional failure points. My choice would be to make a brake line continuous and without bulkhead fittings wherever possible.

In theory you are correct. But that's not necessarily correct with aerospace AN fittings. You don't see airplanes and helicopters falling from the sky everyday due to hydraulic line failures, the reliability factor is in the range of 4-5 nines.

I would be more concerned with a grommet failure creating a metal to metal contact point with the tube which would 100% create a failure in time.

[JohnK]

There's a lot more that goes into achieving that reliability factor in aerospace besides selecting "aerospace AN fittings" (BTW - I very much doubt that anything sold at places most people here typically shop at like Summit are true aerospace fittings) They're installed by highly-trained professionals and inspected at regular intervals. No disrespect to anyone here, but it's very unlikely that this happens on one of our cars to that level. The line I showed in my photos above is clamped at either end of the hole it passes through and insulated with rubber hose. It's not moving at all. Further, it's a stainless steel line passing through aluminum sheetmetal. If there was contact for some strange reason the sheetmetal would wear before the brake line does.

I'm not saying there's only one right way to do things. a bulkhead fitting may be fine. But a fitting can't fail if it's not there to begin with.

[Kbl7td]

If you’re looking for ease and the least fittings, NiCopp. I really have no idea why anyone uses stainless anymore.

[Mike.Bray]

Well the experts have spoken, I'll take my 40 years of AN experience and I'm out!

[OB6]

I chose stainless for how it looks, to be honest, and because I was interested in learning how to bend and flare it. I'm very happy with the results. It's hard to make any argument that it performs better than plain steel or NiCopp. In choosing SS, I also decided that I wouldn't attempt double-flaring but rather stick with the 37 degree single flare for AN fittings.

Totally agree that adding any fitting (bulkhead or otherwise) introduces another potential problem area or risk. IMO no more risk than someone blowing a red light and t-boning my plastic car. Building these cars is an ongoing exercise in risk management.

Now to convince my wife that we don't need roll bars. :eek:

[JohnK]

Well the experts have spoken, I'll take my 40 years of AN experience and I'm out!

No need to get snarky. If you have 40 years of AN experience then you can assemble reliable bulkhead fittings. As a general recommendation for builders, without knowing their experience level, do you disagree that single-piece lines are a safer option?

[Mike.Bray]

do you disagree that single-piece lines are a safer option?

Actually in this case I would disagree. Simply put, passing a hydraulic or any fluid line through a hole in a piece of sheet metal is not acceptable in any industry. It only creates a possibility of metal to metal contact and in the case of an automobile there is a high amount of vibration to contend with. Soft Nycopp would be worse than stainless steel.

Anything can fail. A solid piece of steel can have an embedded crack that can cause a failure. So as an engineer I would look at the possibility of a failure and calculate a number for it. As I mentioned earlier, an AN connection is going to have a reliability rating of at least four or five nines, maybe even higher. I would have to look up the exact number. Considering the entire Apollo Saturn stack used for the first moon landing had three nines of reliability four or five nines is pretty over the top. Chance of failure is never zero but in this case we're talking about one in billions or even trillions. It just is not an issue John.

I worked for a company that manufactured Flight Safety parts for the aerospace industry, mostly Bell Helicopter. A Flight Safety rating on a part means if it fails loss of the ship and life is likely. We made parts like the Jesus nuts that go on the top of the rotor mast. If it fails the entire rotor assembly leaves the ship and remember the glide path of a helicopter is straight down. So I was exposed to some of the standards the aerospace industry does things to. And it's amazing.

I've been fortunate to have been able to see Bell helicopters up close and personal, even getting to peek under the skins as they were being assembled. Absolutely amazing pieces of gear with lots of hydraulic lines everywhere. And lots of bulkhead fittings. Same for race cars, I've looked at tons of Indycars with lots of AN and bulkhead fittings. In addition helicopters and race cars add even more connections when they add dry break couplers. Bottom line is if the connections are tested and don't leak the odds of a failure are so low it's almost incalculable so adding one or two is not negatively impacting your system reliability.

This entire discussion reminds me of a funny story and how we shouldn't worry about things we shouldn't worry about. Years ago there was a car in the Dakar rally that broke the rear end during the race. Apparently the extra weight of the spare rear end they were carrying was the cause of the failure.

John, iIf you're comfortable running a brakeline through a hole in a piece of sheet metal and it works for you that's great. I'm not. Based on my experience and engineering background I would never do it, I'll stick with the accepted industry standard that's worked well for decades.

Mike

[chmhasy]

You should check the state regulation on what type of fitting you can use for brake lines. In Connecticut we cannot use compression fittings.

https://portal.ct.gov/-/media/DMV/20/29/r157pdf.pdf

[Mike.Bray]

You should check the state regulation on what type of fitting you can use for brake lines. In Connecticut we cannot use compression fittings.

https://portal.ct.gov/-/media/DMV/20/29/r157pdf.pdf

Compression fittings are typically rated for only a few hundred PSI, not nearly enough for brake lines. So it's good that they're not allowed.

[BUDFIVE]

I chose stainless for corrosion resistance and AN for a single flare angle and as stated above to learn. Was planning bulkhead fittings for transition from hard to braided lines @ brake calipers and from gas tank/filter to hard fuel lines and from hard fuel lines to braided to the regulator. If I need to join 2 lines I was going to terminate each with a female tube nut and sleeve and connect with a male to male coupler or bulkhead fitting. I wasn’t planning to pass through metal until the rear brake line discussion. Lots to learn, from all of y’all. Thanks

[Nigel Allen]

Actually in this case I would disagree. Simply put, passing a hydraulic or any fluid line through a hole in a piece of sheet metal is not acceptable in any industry. It only creates a possibility of metal to metal contact and in the case of an automobile there is a high amount of vibration to contend with. Soft Nycopp would be worse than stainless steel.

Anything can fail. A solid piece of steel can have an embedded crack that can cause a failure. So as an engineer I would look at the possibility of a failure and calculate a number for it. As I mentioned earlier, an AN connection is going to have a reliability rating of at least four or five nines, maybe even higher. I would have to look up the exact number. Considering the entire Apollo Saturn stack used for the first moon landing had three nines of reliability four or five nines is pretty over the top. Chance of failure is never zero but in this case we're talking about one in billions or even trillions. It just is not an issue John.

I worked for a company that manufactured Flight Safety parts for the aerospace industry, mostly Bell Helicopter. A Flight Safety rating on a part means if it fails loss of the ship and life is likely. We made parts like the Jesus nuts that go on the top of the rotor mast. If it fails the entire rotor assembly leaves the ship and remember the glide path of a helicopter is straight down. So I was exposed to some of the standards the aerospace industry does things to. And it's amazing.

I've been fortunate to have been able to see Bell helicopters up close and personal, even getting to peek under the skins as they were being assembled. Absolutely amazing pieces of gear with lots of hydraulic lines everywhere. And lots of bulkhead fittings. Same for race cars, I've looked at tons of Indycars with lots of AN and bulkhead fittings. In addition helicopters and race cars add even more connections when they add dry break couplers. Bottom line is if the connections are tested and don't leak the odds of a failure are so low it's almost incalculable so adding one or two is not negatively impacting your system reliability.

This entire discussion reminds me of a funny story and how we shouldn't worry about things we shouldn't worry about. Years ago there was a car in the Dakar rally that broke the rear end during the race. Apparently the extra weight of the spare rear end they were carrying was the cause of the failure.

John, iIf you're comfortable running a brakeline through a hole in a piece of sheet metal and it works for you that's great. I'm not. Based on my experience and engineering background I would never do it, I'll stick with the accepted industry standard that's worked well for decades.

Mike

There are regular learnings to be had on this forum. It leaves me slightly envious of all the great industries and careers that are available in the states. I certainly enjoy people sharing their knowledge and their respect during times of debate. Keep it coming!

With thanks,

Nige

[sdeal0527]

Mike where did you get your bulkhead fittings? I apologize if you answered that already, I am making notes for my build , I hope to start this year.

[Mike.Bray]

Mike where did you get your bulkhead fittings? I apologize if you answered that already, I am making notes for my build , I hope to start this year.

I've always had good luck with Earl's (https://www.holley.com/brands/earls/products/plumbing_an_fittings_and_hose/adapters/an_to_an_adapters/) fittings which you can get through Summit. It's easiest to get the part number you're looking for off of the Earl's website and then search for it on the Summit site.

You can get hardline fittings in aluminum, plated steel, or stainless steel. For brakes you want either steel or stainless due to the pressure. And as mentioned earlier, compression fittings will not work for high pressure brake lines.

If you haven't seen this thread (https://thefactoryfiveforum.com/showthread.php?45694-Stainless-Steel-AN-Brake-Lines) it might be useful for your planning.

Mike

[BUDFIVE]

I bought all my Earl’s stainless fittings at Summit Racing-bulkhead (Male T, Male straight, Male 90), Male coupler, Female Tube Nut, Tube sleeves. If using stainless, you will spend more than the $109 required for free shipping :)

[BRRT]

Pegasus Racing is another source for AN fittings. Like Mike said, watch the material, it's easy to choose aluminum accidentally. You don't want aluminum fittings for brakes.

[sdeal0527]

Thanks everyone! I have decided on SS for everything, its been about 40 years since I've got this deep into working on cars . Trying wrap my head around all the fittings and terminology around the brake lines, would rather not have a brake issue.

[Mike.Bray]

Pegasus Racing is another source for AN fittings. Like Mike said, watch the material, it's easy to choose aluminum accidentally. You don't want aluminum fittings for brakes.

AN (Army Navy) is a standard so all AN fittings are interchangeable, you can source them from wherever you like. Pegasus Racing is a good supplier as is Summit. I have seen some variances in quality between brands, I wasn't impressed with Russell, but I always had good luck with Earl's so I stuck with them. You have to be careful with hoses though as each manufacturer makes unique hoses and hose ends. The end that connects to the hose will be designed for a specific hose so don't try to mix and match. For brake flex lines I've made my own in the past but with complete pre-made hoses available today for very reasonable prices that's the best route.

And actually, you can use aluminum AN fittings for brake lines, the street rod guys do it al the time. And I'll admit I've done it on my street rod builds as you can see here.

https://www.imagecoast.com/images/MichaelBray1/build60.jpg

https://www.imagecoast.com/images/MichaelBray1/build64.jpg

However, an FFR Cobra is considerably higher performance than a 32 roadster having bigger calipers, bigger rotors, and more rubber on the road than a typical street rod. For these cars probably best to stick with steel or stainless steel.

[phils88gt]

Since it's 3am and I'm just wasting time on the internet the "airplanes" comment got me.

I have a GA airplane

The hydraulic fluid for the only feed to the brake system is a tin can with a AN fitting soldered into it.

That steel uncoated (that can rust) fitting is connected to an aluminum -4 line that is completely unprotected from corrosion,

The line is single flare on both ends. ( granted low pressure )

The resivor is in the engine compartment.

The line passes through the steel firewall and has a grommet that was cut in half to install it.

Neither end of the line has any clamps whatsoever to support it and the line and firewall are quite free to vibrate.

Once the fluid makes it inside to the masters. The masters are held on by 3x 10-32 bolts.

All fittings are aluminum. Once the fluid leaves the master there is a short section of stanoflex 303 type hose. This is a rubber (not teflon) pressure line that flops around completely unsupported. This needs to move as the masters move around in many small planes.

Everything in the cabin past the outlet hose is aluminum single flare lines with aluminum fittings and nuts. Yes, that is under pressure. When exiting the aircraft the lines turn to hose and continue for 43" each side with hose. ( stanoflex/303 not Teflon )

The hose terminates to an aluminum banjo fitting. This fitting has a 3/8-24 banjo bolt ( that is cad plated steel) and screwed into an unpainted magnesium caliper.

The goal was to be light, and strong enough. I don't think what ever you are planning is worse than this. And this was type certified, has no specific ADs (on the brakes anyway), and isn't particularly prone to any sort of failure.

Phil