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Brake Line Flaring - ISO/DIN Bubble Flares -My Flares do not look like the original flares

4.4K views 16 replies 3 participants last post by  drjim  
#1 ·
Hi guys,

Help.

I have a 1999 model daily driver that just had a steel brake line break.
I am replacing the line and my flares look nothing like what they are supposed to look like.

I want to replace the line with the correct type couplings which are 3/16" M10x1.0mm with ISO/DIN/Bubble flare style rather than an ISO Double Flare.
I have never done Bubble flares and my flares look a lot different than what both the original lines looked like and what I see on-line.

I (of course) cheaped out and bought the cheapest ISO/DIN/Bubble Flaring tool I could buy and I suspect that this is the problem, but it could be the operator.

Are there better quality hand held flare tools that form a better bubble?

The new tubing that I am using is copper washed steel, not Copper/Nickel. I have read that Copper/Nickel is now a preferred material that is rust-resistant and much easier to form. Could this be part of my problem?

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Original Bubble Flare on the right and the one that I am making on the left...
My Bubble flare is missing the bubble.

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The die has formed the bell on the inside of the tube and there is a curve on the top of the flange. I don't think that the tube slipped in the clamp based on the clamp pattern.
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Theslightly curved edge of the flange is supposed to seal against the curved seat of the adapter union. This is different compared to the traditional ISO Double Flare adapter which has a 'volcano' sticking out from the bottom of the adapter which matches the flare shape.

I suppose that this may work, but I don't want to put it all back together just to find that it's leaking.

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The clamp has no recess in it. This forms the flat back of the flare. The die is run down to bell the tube. The instructions indicate that the tube should protrude from the clamp by the distance of the pin on the die. This distance is 5mm.

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5mm pin depth. The curve of the die that forms the flare face is quite shallow. On the right is the die from a Jet brand ISO bubble flare tool. To me, it seems deeper.

Any suggestions and comments would be appreciated.

Dale

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And I found the leak. Not too subtle. It was broken right off.
 
#5 ·
Dr Jim,
I have been looking at a bunch of flare tools last night, and they range from $30 to $300 (Canadian which is 33% less than US).
The one that I bought was $30, with extra fittings, even though they were the wrong ones.
Some of the better ones are from traditional industrial suppliers and are of the traditional style. The differences lie in things like having a wider Clamp (I'm not sure of the official name, it looks like a horseshoe to clamp the screw that drives the die into the holder) so that the die lines up in line with the tube. The cheap ones are thin and can be off axis. They have side clamps as well to hold the two holder bars together rather than two wing nut screws. This seems to make the two bars line up a little tighter. The wing nut screws leave enough side-ways movement that the flare on the tube can be mal-formed.
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$250 tool on the left and $30(ish) tool on the right.

One of the things that my $30 special did poorly was to leave marring where the securing bars grabbed the tube as part of the clamping action.

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This copper washed steel tubing has been marred so deep that some of the steel tube is exposed. This will rust over time. You can see a straight line where the two clamp bars meet. If you aren't careful to make sure the surfaces are even, you will see the flare distorted.

There is a second type of hand-held flare tool that doesn't use thread-like clamp 'things'. It uses two bolts to hold two halves of the clamp dies together.
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This is a double-flare tool, but the concept is the same. You tighten the two bolt heads to clamp the two smooth die halves to the tube. Then you use a wrench or a ratchet to drive the die into the tube to form the flare. It seems a bit finniky to be tightening 3 bolts, but it seems to leave smoother tube ends.

For all tech weenies (and aren't we all), there is a third type that is somewhat less compact, but probably makes the most consistent flares.

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A vice mounted turret head tool. It uses two clamp halves to clamp the tube and you then rotate the turret to the correct die and throw the blue lever.
It's definitely not something to use under the car, but it looks to me like you will get the most consistent flares with. There are Taiwanese versions for C$290 or Chinese ones for C$120. The one above is Taiwanese.

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The traditional style flare tool on the left and the turret style one on the right.

I saw a web site where the blogger indicated that this was by far the better way to go.

reddit - My experience with two different brands of bubble flare brake line tools

I'm giving this one a try. My existing steel lines were so bad a shape that I couldn't patch the tube on the car. I had to take the whole line out to measure it. As a result, the size is not an issue for me.

Sigh. Nothing is ever cheap.

Dale
 
#3 ·
The curve of the die that forms the flare face is quite shallow. On the right is the die from a Jet brand ISO bubble flare tool. To me, it seems deeper.
I agree. It looks like the die is the incorrect one. You need one that does a deeper chamfer. It looks like a 45 degree to me in the photo of your original tube.
 
#4 ·
That's what I thought, but as they say a good craftsman never blames his tools. I am definitely NOT a craftsman. It's the darned tool!!!!!
It seems to be making these quite consistently, just flat.

I also don't like the fact that the holder doesn't have a recess that contains the die when it's forming. I don't think that it would be any stronger, but when you are trying to set how far the tube protrudes out of the holder, you have to measure with the tightening wrench that has a rebate to set the distance. With ones that have a recess, you just make sure that the tube is flush with the top of the holder. When you're upside down in the engine compartment it's one more thing to try to hold.

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This works, but it would be easier if there was a recess in the tool and you just had to make sure the tube was flush with the top of the tool.
The threads in the tool that grip the tube are not very clean. I've chased them and lubed them, but they leave pretty serious marks on the tube.


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There is another type of tool that has a screw-in stop to limit how far the tube enters the tool before you tighten the clamp, but it's probably more work to thread the stop in and then back out again. You have to thread in the two bolts visible to clamp the tube and then thread in the die on the right. It seems somewhat smaller if you are doing flaring on the car. This one is an SAE double flare, but there are ones for DIN/Bubble flares too.

If anyone has luck with a particular brand of flare tool, I would love to hear it.

Dale
 
#6 · (Edited)
I've been digging a lot at what exactly a DIN/ISO/Bubble flare should look like.

There isn't really all that much good information.

What I've been able to gleen is the following:

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The commonly used brake line is now 4.75mm, which is 3/16"
It's a double flare but not folded completely back on itself. It appears to have changed slightly. Initially, this type of flare was the German DIN standard. Later, Japanese and American car makers started using them and the standard became an ISO standard. It's commonly called a bubble flare because of it's shape.

I have heard of the first step in making an inverted double flare as being a 'Bubble Flare' but that is not how they should be made. There is also an SAE Bubble Flare which is an obsolete profile used on British Girling brakes starting in the 1950s.

The back side of the flare should be 90 Degrees so that the flare nut can push the flare into an adapter to get it to seal.

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The ISO/DIN/Bubble nut has a flat end that pushes on this 90 degree shoulder. The cone shaped tip of the bubble bears against the cone shaped portion on the inside of an adapter.

As a result, the exact shape of the flare can vary and still work. My concern about the flat shape of the bubble flare my cheap tool are forming is there not something to worry about.

Bubble flares should not be reused more than several times. I guess the bubble can start to collapse after being tightened too many times. I suspect that the flat bubbles that the cheap tool makes are almost entirely collapsed already and not as prone to leaking after reuse.

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There are quite a few variations in shape of the bubble flare that I have seen. I assume that all will work.

Finally, I always thought that steel or stainless steel brake lines were required for DOT and safety reasons. This is no longer true.
The steel lines rust (through as I found!), and both the steel and stainless steel lines are difficult to bend and to flare.
In earlier decades, soft copper tube had too low a burst pressure to stand the pressures created by a brake system so they were/are illegal to use (and just stupid too)

I have seen and used steel tubing that is copper washed to prevent rusting and as long as you do not abrade the copper off, they are an improvement. They still are hard to bend and require a lot of force to flare. It has several fancy names, such as KuNiFer (Copper/Nickel/Ferrous).

Finally, there is Copper/Nickel tubing
Originally it consisted of:
  • 87.8% Copper
  • 10% Nickel
  • 1.4% Iron
  • 0.8% Manganese
Each manufacturer has tailored the exact composition, but it is now legal (and preferred in fact) to use Copper/Nickel tubing. The burst strength is actually higher than steel and is more rust resistant than Stainless Steel.
One of the big differences between the different brands of Copper/Nickel tubing is the wall thickness.

For 3/16" od tubing:
Less expensive brands have a Wall Thickness: 0.0049” 0.125mm This makes it harder to bend the tubing without collapsing it in tight radius turns.
More expensive brands have a Wall Thickness 0.028 0.711mm. This makes it much easier to bend the tubing, even by hand. This thickness will still let a flare tool die to enter the tube without issue.

I never knew there was so much involved with brake lines.

Dale
 
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#7 ·
Well done, Dale! Thanks for the education. I don't recall ever hearing of "Bubble Flares". I made the good old fashioned Double Flare type. The flaring tool I used to have looked like the expensive one with the two bars to grip the tubing. It made very nice flares, but that tool vanished some years ago.

This should be a sticky!
 
#8 ·
Thanks Jim,

But the truth is, it's the blind leading the blind. Interestingly, Toyota seems to have switched over quite recently from SAE Inverted flares to ISO/Bubble flares.
I was trying to get this car on the road as a daily driver and I end up having to buy new tools to get it done. So much for a weekend job.

The reason for Bubble Flares was to reduce car assembly costs, not to improve the quality or reliability of the brakes! A single machining step versus two for the Double Inverted Flare. And at least initially, the fittings were not supposed to be reused.... Lovely for someone keeping an old car alive.
It sounds like a case of manufacturing ease versus maintenance ease. You hear stories about of how some Dodge vehicles had to have a wheel taken off in order to change a battery! True story. Yeah, they sure love their customers. Toyota to their credit kept using the better brake flare style for far longer than other automakers.

I'm pretty sure our Mk 2 only used Inverted Flares for everything.

As far as good old American manufacturers go, the car I'm working on is a 1999 Ford. This design was done in 1995 and was released in 1996. Sheesh.

However, it sure sounds like Copper/Nickel brake line is the bomb. I've got some on order too. I will definitely use it as necessary on all my cars. And they look nice

Dale
 
#9 ·
You're welcome, Dale. You could easily write up a post on flareing and get it made into a sticky. I'm thinking of doing one on Fusible Links. There's so much bad/wrong info on them, and beginners get confused. I really dug into this during my upgrade of the wiring harness for my new headlights, 120A alternator, and Spal cooling fans.

ALL the high-end shops and restorers use the Copper/Nickel tubing now. From what I've read, it not only tkakes flares better, but it's easier to form, and does NOT rust. Cool stuff. Would have been nice to have it back In The Day...
 
#10 ·
Yup,

I looked at the brake line that was totally destroyed on this car and shake my head. But, I saw copper and thought peope were insane until I read more about them.

An article on Fusible Links is really interesting. If one blows a link, you don't wat to 'guess' at a replacement for them. You don't want a fuse replacement to be blowing all the time, and even more importantly, you really don't want to install a Fusible Link that is poorly chosen and allows your car to burn down by NOT blowing.

I am looking forward to this article.

Dale
 
#11 · (Edited)
Well, here are my results with the turret flare tool that I bought.

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Flare made using cheap flare tool - top
Flare made using turret type flare tool - bottom

The die was definitely the reason for the flat look on the flare that I made using the cheap flare tool I bought.
The tube body itself is a lot less damaged behind the flare on the turret tool made flare. There ARE several lines that line up with the parting line of the two die blocks, but they seem to be very shallow.

I used Nickel-Copper tubing 3/16" OD with 0.028" wall thickness.
I deburred the inside and the outside with a deburring tool, but I think I have to work on using it. If you aren't careful it's easy to leave cutter marks which can cause tubing splits.

The kit came without any die lubricant, so I used brake fluid. I'm not sure if this is adequate, or if the forming die (I don't know the correct terminology) on the turret is rough, but when I finished the forming the flare and and released the forming handle, the springs on the unit were not enough to release the tube from the forming die. I had to pry the turret back with a screwdriver.

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Tube stuck in the forming die. The face of the forming die.

I've heard that one should not use a hydrocarbon based grease, so I'm not sure what would work the best. Someone has mentioned WD-40 which may help. I've been cleaning the tool with Q-tips to get rid of the metal debris.
Any recommendations for this?

Overall, the tool works really well and makes nice quality flares, but I suspect that I have to learn the little tricks to make it more consistent.

Dale
 
#13 · (Edited)
Beautiful flare, Dale! These seem to require a lot more attention to detail and proper tooling to come out that nice. I think the recommendations on lubricating the tool and tube are due to worry about getting oil into the brake fluid. I'm not sure what oil in your brake fluid would do (attack the seals?), but I always remember reading and being taught to use ONLY brake fluid as lube in the system or components. I think the tooling has to be very clean, too. Yes, using a deburring tool takes practice to get a nice part, but it also take the right type of tool. What are you using to deburr the cut ends with? Is it one of the "Double Cone" types?
 
#14 ·
Jim,

This is the flaring tool that I have:

4LifeTimeLines - Rimming & Deburring Tool for 3/16" to 1/2" Tubing

It seems to be pretty good quality, but

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There are only 3 cutters. While this makes the tool symmetrical to stay in the middle of the tube, one has to use a deft hand to ensure you don't make too deep a cut.
When stopping on the outer ream, I haven't been lightening up enough and this is the result:

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Right on the end, you can see several indents. I'm sure that those are caused by the cutter on the reamer.
I've done some without the outside reaming and these marks are not there. Again, a bit of practice. And me with ham fists.

I suspect that if you form the lines off the car that you can clean the flares in a jar with solvent to get rid of the cutting solution. Additionally, I think that one should be chasing the inside of the tube after forming. There is a lot of junk in there.

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You can see a wire of cutting semi-attached to the swaged end. I think that this was cut during the forming process, not a result of the lack of deburring.
I think a chase with a jeweler's round file and then a sonication in a solvent to make sure than any debris is removed would work.

I'm trying a hydrocarbon based grease on some test flares and also silicone grease as used on brake caliper pins as a cutting lubricant.

Acetone and Hexane are good degreasers, and I suspect a quick immersion and sonication of the flared tube end will remove any significant concetration
Xylene, Toluene and Mineral Spirits will readily dissolve Silicone. There is a a filler in silicone grease, amphorous silica, essentially small glass beads that thicken the silicone grease up. This is used in toothpaste as a cleaning agent. I suspect that once the silicone is dissolved, the silic will readily be removed with sonication.

Nothing is as easy as I first imagine. The flares don't look bad, but I am really going to have to up my game to make nice looking ones.

Dale
 
#16 ·
From one nerd to another; You betcha!

More than half the fun of having an old car is being able to fool around with it and learn things about it.
I'm always amused by watching youtube vblogs about doing something that appears to be really simple. When you try to replicate it, you realize that there is a LOT more art and skill involved than there appears to be.

Oh, and I officially retired this Friday (Friday the 13th!) so I've got enough time on my hands to spend it going 'over the top'.

Power to the old ones :ROFLMAO: