ShawnG UltimaDork
11/24/20 10:59 p.m.

In another discussion, I offered to teach Lof8-Andy how to flare brake lines perfectly every time. He said I should put up instructions so here they are.

In these photos, I'm modifying a hydraulic brake conversion on a 1931 Model A Ford but the principles apply to anything. 

Number one is: Buy a good flaring tool. The cheap, offshore ones don't clamp the line properly and let it slip, causing headaches.

Everything else is probably in your shop already.

First step, cut your line to length with a tubing cutter and slip the flare nut on. 

ShawnG UltimaDork
11/24/20 11:01 p.m.

Next, make sure the end of the tube is cut square to the line. If it isn't, clean it up with a hand file so it's square.

Then, use a countersink or twist drill to take off the burr that the wheel on the tubing cutter leaves in the end of the line. Leaving this behind is usually what causes wonky flares.

When you're done, flush out the end of the line with some brake cleaner to clear out any shavings.

ShawnG UltimaDork
11/24/20 11:07 p.m.

Put the clamp bar on the tubing but don't tighten it yet. Make sure the flare nut is on the tube!

The double flare die that fits the tube is also the depth gauge for how much material should stick out of the clamp. Set the stickout to the shoulder of the die.

Tighten the clamp down, starting with the end closest to the tube. Ever wonder why the wing nuts have a big slot in the end? The flaring tool handle is used to tighten the clamp down until there is no gap in between the halves.

ShawnG UltimaDork
11/24/20 11:15 p.m.

Next, place the double flare die into the end of the tube and snug the flaring tool up to hold the die in the end of the tube. Double check that you've put the flare nut on the tube!

Tighten the flaring tool down until it seats the die as far as it will go. 

Remove the flaring tool and the die, check your work. If the flare is off to one side or cracked, cut the end off and start again.

If it's ok at this stage, put the flaring tool back on without the die and run the tool down to seat the double flare you just made.

Evidently, I forgot to take a picture of this step.

Don't seat the flaring tool completely, just press it into the end of the tube enough to give it the proper shape. 

The flare will crush against the seat in the wheel cylinder and seal tight. All of my fittings have been leak-free since I learned to leave a tiny bit of crush in the flare so that it forms to the seat in the fitting it's being installed into.

Another tip, if you're putting an old line back into a new cylinder and it won't seal, loosen and re-tighten the fitting a few times to crush the tubing and make it seal. If this doesn't work, it's time for a new flare.

Hope that's clear enough for everyone.

bearmtnmartin SuperDork
11/25/20 12:22 a.m.

Good job. And in my humble opinion cheap Chinese flare tools have caused more flare despair than any other thing. Until you try with a good one you don't realize how important precision manufacture is.


ShawnG UltimaDork
11/25/20 12:58 a.m.
bearmtnmartin said:

Good job. And in my humble opinion cheap Chinese flare tools have caused more flare despair than any other thing. Until you try with a good one you don't realize how important precision manufacture is.



This x1000

I know people think Snap-On is crazy expensive but it's not really that bad. This is a Blue-Point flaring tool which is their downmarket brand. Blue-Point is not made by Snap-On but is supported and warrantied by them and I've had no problems with the quality. 

This one is a shop tool but if I had to guess, it would probably cost around $100 - $150 Canadian. My Blackhawk flaring tool that I have at home works just as well and it cost me about $80 when I bought it.

I've never tried one of the new hydraulic units because they're so costly and these ones work so well.


Lof8 - Andy
Lof8 - Andy SuperDork
11/25/20 3:11 p.m.

Excellent. Thanks!

Patientzero HalfDork
11/25/20 4:26 p.m.

I get perfect flares 100% of the time when I forget to put the nut on.

Lof8 - Andy
Lof8 - Andy SuperDork
2/3/21 5:40 p.m.

So I'm finally digging into this project.  I had a bubble flare tool laying around that I thought would produce the right flares for my application - bmw e36 3/16" brake lines.  But they're not right.  What do I need to match this?


i bought a few short steel lines from Napa to do some practicing and I was getting this:

Lof8 - Andy
Lof8 - Andy SuperDork
2/3/21 6:11 p.m.

The googles tell me a bubble flare is the correct flare for bmw. Maybe it deforms a bit as you tighten the nut to the fitting?  I dunno. But I ordered this flare tool from summit that has a lot of good reviews. 

Lof8 - Andy
Lof8 - Andy SuperDork
2/6/21 10:38 a.m.

wow. This Summit tool is the E36 M3!  Perfect flare first try that is a much better match to the profile I'm looking for. 

ShawnG UltimaDork
2/6/21 12:17 p.m.

Looks good!

Going to have to look into that tool. Can it be used in-hand or does it have to be held in a vise?

Lof8 - Andy
Lof8 - Andy SuperDork
2/6/21 12:33 p.m.

In reply to ShawnG :

I think a vice is needed. I don't think you could counteract the force of the big lever while holding it in your hands. But I do recommend this thing for lines that need fabricated and are not connected to the car. 

AngryCorvair (Forum Supporter)
AngryCorvair (Forum Supporter) MegaDork
2/6/21 4:08 p.m.

In reply to ShawnG :

TIL to not crush the berkeley out of the double flare step.  Thank you for that!

k20a2DC2 New Reader
4/20/21 4:15 p.m.

what about line or tubing what do you guys recommend I'm currently pricing materials to do prop valve 40/40 from a civic to an Integra. Going 2 lines from brake master cylinder/ to prop valve, then two lines from prop valve to left front and right front wheel, and probably just attach rear to prop valve or ad tubing to them depending on length. Unless rear lines are in bad condition then I'll just replace them.  The only issue I believe my car has inverted flare and are metric.

Any tips or tubing recommendations? 


AngryCorvair (Forum Supporter)
AngryCorvair (Forum Supporter) MegaDork
4/20/21 5:31 p.m.

In reply to k20a2DC2 :

NiCopp tubing is your friend

wawazat Dork
4/21/21 5:58 p.m.

Another vote for the Summit tool.  Its sold by a bunch of different suppliers all over the place including Eastwood.  I also like the NiCopp tubing.

SkinnyG (Forum Supporter)
SkinnyG (Forum Supporter) UberDork
4/21/21 7:26 p.m.

I picked up one of these recently from Amazon for work.  To borrow.  For me.  Of course.

Scott_H Reader
5/12/21 5:55 p.m.

I am disappointed.  I wanted to learn about these:

DoninMedford New Reader
6/20/21 9:40 a.m.

Your tubing cutter should have a deburring tool to take off the burs from cutting unless its the mini version. After all the basics have been followed, its been a tool change that's made the biggest difference in the ease of flares personally.  I put my 20 year old Snap-On kit on craigslist when an employer got the Mastercool flaring tool a few years ago and let me use it on a restoration.  I purchased my own, it was that much better.  For someone that rarely uses it, probably just suffer through with a standard USA made style as shown above.  Yes, you still have to deburr the tube cut and follow the basics, but the way it holds the tube and forms the flare is much nicer.  Use what you are comfortable with, but I haven't regretted the swap at all. Bubble flares, other specialty flares are not a problem. I got mine as a used store return off eBay, it helped with the price difference and its one of those tools that work so well I regret not springing for it sooner. 

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