Thread: double flare brake lines

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OK.. so they say education is expensive.... gotta accept that first I guess.

I pulled the trigger on a hydraulic double flare tool. Works sweet on steel lines ( 3/16 ) but simply won't hold the tubing for the stainless. I'm cranking down on the hold pin as hard as I can without putting a tool on the handle. I had even considered adding some extra hold down bolts on the die, but if I put enough stress on the die to hold the tubing, I'm probably risking breaking the tool. I figure that if the manufacturer wanted you to put that much clamping pressure on the die, then it would have been made different.

I know the concensus is that you can't double flare stainless, but I figured I may as well try it since I have the tubing and the tool.

So, new fork in the road. Should I get the AN fittings, and a 37 degree flare tool, or just go with standard steel lines. I'm leaning towards standard steel at this point. After all I would probably need another super tool to do the flare, right?

I got the s/s fittings for the 45 degree double flare: it should be no problem to use them with standard steel tubing?

At the local parts store, they have some coil tubing with a grey coating on it. Supposed to be super corrosion resistant. Anyone familiar with it?

I have the same hydraulic tool and had the same bad luck with stainless. IF (means about 20% of the time) I could hold the stainless, the stuff cracked when I did the second flare of the double. If it didnt, I screwed up the other end of the tube. If I got one that looked about right, it leaked when I installed it unless I put a monster torque on the fittings. I finally gave up and bought pre-made lengths, cut one end off to the right length and flared that. Worked fine.

My 91 Caddy has the corrosion plated lines on it. Replaced the rear lines this year. My 94 PU got them replaced last year. I'm not really impressed with the plated lines other than they look better. My 61 pontiac srill had the original unplated but aluminized lines in good condition when I sold it last year, but they were rusty on the surface.

Update. I got the tubing with the grey coating. POLY ARMOUR steel tubing is the name of the product, got it at Advance Auto. Good stuff, the coating is flexible enough that it does not chip or flake when bent. The tubing took a double flare wonderfully, looks real nice. Having a quality tool always makes the job go smoother.

Up to this point, I thought I had a piece of crud in the lines acting as a check valve, which is why the brakes locked up. BUT.. I found the real culprit. the Ebrake cable on the drivers side was rusted up in its sleeve. Aslo, the springs and other brake hardware is shot.

I'm gonna have better than 1500$ in these dam brakes before I am thru...

I have a manual double flare tool and have no problems double flaring stainless. Actually, never had a piece crack. Are there differences in tubing alloys? I got mine from Inline Tube. Al.

Stainless work hardens so severely that double flares are impossibly difficult--sometimes just to single flare ss I've had to anneal the end of the tubing to prevent splits---

what alloys have you been able to do doubles on????

























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Inline Tube told me that a tubing cutter will work harden the lines...they said to cut it with a cutoff wheel instead of a tubing cutter.

however they are cut they will need to be champered/deburred---And clean,clean,clean,clean---Did I say that you need to clean them????

37 deg for stainless. Use AN fittings.

You really need dead soft annealed SS tubing. 304 is probably the softest in this condition. It does work harden rapidly.

Jerry is right on ...deburr everything and make it smooth or it will crack.

I cut and bent all my brake lines using the stainless kit from Speedway and took the lines to the nearby John York turnkey Cobra shop for the flares. Although I still have one annoying leak, most of them are OK. John York merely put them into a vise-jig and hit the ends with a double-flare tool using a hammer. For the leak I am just going to make a new line and take it to John York for another try. I do not know where to get the tool that John used but it is a simple clamp-on to put in a bench vise with a cone inset and a punch tool to be used with a hammer for the 37 degree double flare and AN fittings. I have recently been messing with 3/8" steel line for a fuel line and I thought the 1/8" stainless line was tricky but actually it is easier to make complicated shapes with the thin stainless than with the larger 3/8" steel. Long ago I worked on an assembly line putting flares on copper tubing in refridgerators but that is childs play compared to either stainless or plain steel. The truth is that you probably end up with a few wasted parts after trial and error.

Don Shillady
Retired Scientist/teen rodder

A leak is not always the flare...look closely at the mating cone on the fitting. IF you can see any depression or indentation, the seal is suspect. Replace the fitting and try again.

This Poly Armour tubing hasn't shown the first indication of wanting to crack or split. Haven't gotten to the leak check portion yet, but the flares this Mastertool inc. hydraulic tool makes look flawless. For cutting the tubing, I just chuck it lightly in a vise, and put a hack saw to it. Then I smooth the end with a fine tooth file. Tap it a couple times with end down to knock out any filings, and it's ready to flare. Did I mention this tool works well? E-Z! Inasmuch as it is hard to justify this much for a single tool, which I may never use again, what price can you put on easy!?

The rear lines I bent up went in place with minimal tweaking. I bent them to match the old lines, only used a bending tool to make a U on one line. Stuff bends easy, doesn't try to kink.

I am thinking the stainless nuts were a real good idea, regardless that the stainless tubing was a bust. The dark grey finish of the lines looks nice against the rust and GA red clay on the chassy.