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Bubble flareing the brake lines


fun car guy
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So I'm back working on the brakes on my '89 Reatta, specifically replacing the valve unit but I'm having trouble getting a bubble flare to the unit.  My flaring tool has adapters for 4 3/4mm which is apparently too small so no matter how I try, it simply pushes the tubing down instead of flaring it.  The next size in my kit is 6mm but I'm concerned about possibly splitting it.  What have you guys found to be the correct size and technique for the job?

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That should be the correct size. 3/16" tubing is 4.76mm. I sounds like the clamp isn't holding the tubing as it should. It should leave slight marks from the serrations on the clamp. The inside diameter of the tubing needs to be cleaned up and squared. I actually use a small drill bit to clean up the interior diameter to be sure the center point of the die slides into the tubing.

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15 hours ago, 2seater said:

That should be the correct size. 3/16" tubing is 4.76mm. I sounds like the clamp isn't holding the tubing as it should. It should leave slight marks from the serrations on the clamp. The inside diameter of the tubing needs to be cleaned up and squared. I actually use a small drill bit to clean up the interior diameter to be sure the center point of the die slides into the tubing.

Thanks for clearing up my concerns about the size but the clamp will not hold!  It just scrapes lines on the outside of the tube pushing it down.  I've filed the edge of the open tube square and even but am confused that I can't get a flare no matter how many times I try.  Have thought about heating the tube to remove any temper and help.

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Are you working with the original tubing from the car? Some types are definitely tougher than others. What flaring tool are you using?

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Yes, I believe these to be the original tubing.  I now see they recommend applying a little lubricant to aid the flare so maybe that will help but might just make it easier for the tubing to slide instead of flaring.  Here's what I'm using:

image.thumb.jpeg.9bbe9e86b41069695f1906823856fe72.jpeg1307781902_1(2).thumb.jpg.ff7e7b31b3ee66410f0015e9945d1913.jpg

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Same one I have. Don't lubricate the part that is clamped in the holder. Maybe a dab on the end where the die has to form the end of the bubble may help. I am guessing you are working around the Teves valve block? Tighten the clamp on the end nearest the tube size you are working with first, then the one toward the other end which should provide greater leverage to pinch the tube. Good luck

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Yes, it's the line to the rear wheels.  I had to cut it since I couldn't get the fitting to move.  I'll put a little dab of grease on the die and try again.  If successful, I'll be able to finish the installation of the replacement valve block on the master and be able to bleed the lines and I'll finally be able to get her on the road for detailing.  Thanks again for your help!

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If you are making brake line on car buy  titan 51535 flare tool on Amazon,  your best friend for 3/16 lines on vehicle.  Sorry not a purist,  but it works. There are other tools that work great for making lines off vehicle. 

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2 hours ago, Sam car said:

If you are making brake line on car buy  titan 51535 flare tool on Amazon,  your best friend for 3/16 lines on vehicle.  Sorry not a purist,  but it works. There are other tools that work great for making lines off vehicle. 

Incorrect style flare for a Reatta. It looks like a decent tool but not for this application.

Reatta uses metric bubble flare, not inverted flares.

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15 minutes ago, 2seater said:

Incorrect style flare for a Reatta. It looks like a decent tool but not for this application.

Reatta uses metric bubble flare, not 

This is a 2 step tool, it makes a perfect bubble flare and than you flip the die and it makes a perfect double flare. I was just trying to help. I use it on my 89 and my son's 94 tracker. 

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I understand the principle but there are subtle differences in the shape, primarily the back side of the flare where the nut bears against it. The bubble flare is square and 90deg to the tube, the inverted is less so. It may work perfectly fine and I have no personal experience doing so. Photos are of the two styles of flares and the nut.82B0A026-AABA-4565-923B-DE7EDD579582.thumb.jpeg.10757df13f7f99cd792a5ac168b4afa6.jpeg

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On 6/12/2022 at 5:55 PM, fun car guy said:

Yes, I believe these to be the original tubing.  I now see they recommend applying a little lubricant to aid the flare so maybe that will help but might just make it easier for the tubing to slide instead of flaring.  Here's what I'm using:

image.thumb.jpeg.9bbe9e86b41069695f1906823856fe72.jpeg1307781902_1(2).thumb.jpg.ff7e7b31b3ee66410f0015e9945d1913.jpg

 

I redid one of my Reatta's lines with the same set. I found the crucial instruction is the last part of Step 1: chamfer outside of tubing. That means round off the sharp edges with a file so the flaring tip slides smoothly on the brake line instead of digging into it. Put only a tiny amount of oil on the tip itself.

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Thanks to all of you!  It makes good sense that you would gently file the outside rim where the tubing is cut and to apply a little grease to encourage the tubing to flare.  Not having any experience doing this, I was simply trying to make it work without either.  You're advice is very much appreciated and I'll let you know how it goes! 

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