Making a Bubble Flare for Brake Lines

working on a car's brake line
  • 1-2 hours
  • Intermediate
  • 50-75
What You'll Need
Double flare tool kit
Tube cutter
Tube nuts
Steel brake line

Most cars use double bubble flare brake lines. The double flared line is positioned alongside a brake component (either the brake hoses on the slave cylinder, or the outlet fittings or master cylinder inlet). Flare refers to the brake line tubing’s end part, which is flared or opened to 45 degrees angle. Then the flare is folded above itself, creating a double and secure flare.

Creating double flare brake lines is very challenging. As it is possible to perform, most people eventually fail in productively making a constant double flare. It is because of the fact that creating a double flare needs precision. When the flare is not ideal, the line will ultimately suffer a catastrophic breakdown of the car’s braking system, which could trigger serious damage or death to anyone in the car. If you are going to try making a double flare, you will need a lot of patience and specialized equipment.

Step 1 - Place the Tube Nut

Put a tube nut above the steel brake line’s end, so the threaded end will face the brake line’s end that you will be working on. Ensure that the end portions of your brake lines are free from any burrs and are level and accurate. You may require using a metal file and a tube cutter to attain this. Put the brake line’s end into your flaring clamp, so the brake line protrudes out of the top portion of the clamp.

Step 2 - Prepare the Brake Line Anvil

brake line

Arrange the brake line anvil utilized to make double bubble flares along the clamp’s face. The anvil contains two sides. One side is raised, while the other side is flat that fits into the tubing’s center. Place the anvil’s flat side alongside the clamp after the brake line. Regulate the uncovered length of the car’s brake line. There’s a line along the anvil’s center which specifies how far the brake line’s end needs to be uncovered. Again, alter the end of the brake line till it is equal with the anvil’s line. Then tighten down the anvil, which is very crucial. The brake line should not move when you tighten it. Put the raised anvil’s end into the middle portion of your car’s brake line.

Step 3 - Make Double Bubble Flare

Finally, put the flaring tool above the clamp and anvil. The anvil holds a big screw along with a 45-degree angled bit along its end. Next, you need to tighten the flaring tool so the line’s end bubbles out. Make it tighter until the anvil assembly is flush next to the clamp. Remove the anvil and flaring tool afterwards. You will observe that the line has made a bubble. Then, if the line has shifted at all, you should re-do the line and begin again.

Install the 45-degree flaring tool end alongside the tubing’s center then tighten again the flaring tool. As you perform this, the double bubble will fold above itself, making the 45-degree double flare. Then, the flare should be absolutely square and accurate, and be completely centered for it to maintain in your car's brake system.