How to Flare Brake Lines

Co-authored by Matthew Rava

Last Updated: November 17, 2022

Flaring brake lines ensures a leak-proof connection without extra materials or sealants. If the brake lines aren't properly flared, you can lose fluid that will cause your brakes to fail. This article will explain how to flare your brake lines using single and double flares.

Steps

1
Measure the length of brake line needed with measuring tape.
2
Don hand and eye protection.

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3
Cut brake tubing to the desired length with tubing cutters or a hacksaw.^{[1]
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- Cutters will cut round tubing squarely without causing burrs. You will have to remove burrs if you use a hacksaw.^{[2]
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4
Use a flaring tool or a double flare tool to form the tubing's flare.^{[3]
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- The instructions for both types of single flare tools are given below.
5
Put the cone of the tool over the end of the tubing.
- Lower the cone down until it is centered over the tube's end.
6
Turn the advance screw to move the cone until the part of the tube being flared is firmly against the countersunk recess of the bar.
7
Inspect the new flare for cracks, splits, or other imperfections. If the line is damaged at all, replace it with a new one.

Method 1

Method 1 of 2:

Generating Tool

1
Place the cone over the end of the tubing and move it down until the cone is centered.
- On a generating flare tool, the flare is formed in the air instead of in the recessed part of the bar.
2
Turn the advance screw several revolutions. Check the manual for the number of revolutions needed for the flare size you need.
3
Check the new flare for any imperfections such as splits. If you end up with any damage, even a hairline crack, toss out the brake line and try again with a new one.

Method 2

Method 2 of 2:

Double Flaring Tool (New Standard)

1
Clamp your tubing into the flaring bar.^{[4]
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- Ensure the depth is equal to the edge of your tubing size insert.
2
Install the yoke and use it to advance the cone into the tube until a bell shape forms.^{[5]
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- Remove the insert and finish advancing the cone into the bell.
- The bell shape of the tube forms the double thickness flare.

Community Q&A

Question

Can I use a single in an application where a double flare was used?

Uglymug18

Community Answer

No. Double flare is used in high pressure ABS applications for a reason. A single flare is more likely to spit under high pressure, causing break failure.

Warnings

Consult your tool's user guide for specific instructions. Tools' instructions can vary from manufacturer to manufacturer.

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