Bubble Flare vs. Double Flare vs. Single Flare: Which Is Best?

If you need a brake line flare, you can choose a single flare, double flare, or bubble flare. But which is the best for your application? The flare type you choose depends on your car model, as it can be a double flare or bubble flare.

What is clear is that you should never use a single flare brake line in your car. It will not just withstand the high pressure in the braking system.

Double flare and bubble, which one should you make for your braking system? Find out as we describe flare types in this article.

Why Is A Good Brake Line Flare Important?

It’s better not to take to the roads with a faulty brake system. In many cases, brake failure is due to brake fluid leakage or worn-out brake pads. But before that, have you wondered how your car slows down and eventually stops when you apply brakes?

A car brake system uses a simple principle. It comprises brake pedal, piston, brake fluid, cylinder, brake pad, and brake line flare. When you apply slight pressure on the brake pedal, the piston pushes against the brake fluid in the cylinder. Brake fluid is incompressible, allowing equal distribution of the applied pressure throughout the hoses.

The slight pressure applied by stepping on the foot pedal amplifies as it is transferred to all connected wheels. The force pushes the brake pads against the wheel disc. The friction created resists the wheel rotation, causing your vehicle to stop. But what is the role of brake line flare?

Brake line flare ensures a leak-proof connection. As a result, all the applied pressure is transferred to the wheel to stop your car. Otherwise, the brakes may fail.

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Brake Line Flare Types

Single flare vs double flare vs bubble flare
Brake line flares are very crucial components of a braking system.

Brake line flares are very crucial components of a braking system. But what are the different types you are likely to find at the end of your brake line? There are two main brake line flare types: double flare and bubble flare. The third one, single flare, is rarely used.

  • SAE/Double flare: It appears like a funnel inserted into a tubing. This type also looks inverted and is usually at 45 degrees. If you have an American or Asian car, your car likely has it.
  • DIN/Bubble flare: It looks like a button at the end of the tubing. If observed from the back, it makes an angle of 90 degrees to the tubing section. DIN is commonly found in European cars.
  • Single flare: as the name suggests, it is flared once in a conical shape. It is not common because it can’t handle high-pressure braking systems. Single brake line flares tend to crack and leak easily.

Most brake flare lines are made of metals, which can be galvanized steel, stainless-steel, or nickel-copper alloy. The last two are preferred for any type of brake line flare because they are impervious to rust and highly resistant to corrosion.

A video about brake line flare guide.

Double Flare vs. Single Flare vs. Single Flare

SAE/Inverted Style/Double Flare

Double flare
The double flare is used in the braking system with a female socket with an inner side popping like a volcano.

As expected, double flare is used in the braking system with a female socket with an inner side popping like a volcano. Using this flare line in the wrong socket will not create a tight seal. If you do that, leaking will be inevitable.

The double flare line remains the most popular for its strength and reliability. It is durable and studier and can handle high pressure in the braking system. The double flare is the best choice if the socket at the end of your brake line matches. This type is also very tolerant of variations in production.

Single Flare

single flare
A single flare line has only one lip that is not folded over.

A single flare line looks much like a double flare, but it has only one lip that is not folded over. It can fit in the socket where double flare fits but is not used in the braking system. The reason is that it is not sturdy enough to handle high pressure in the braking system. It cracks easily, leading to leakage and brake failure.

DIN/ISO/Bubble Flare

bubble flare
Bubble flares are used in the brake line where the socket has depression or a funnel-like shape going inwards.

Bubble flares are used in the brake line where the socket has depression or a funnel-like shape going inwards. Once again, you should never use it in a socket meant for double flare. The result will be a leaky braking system that may fail.

To make a double flare, you must first follow the procedure for a bubble flare. So, we can say that it is easier to make. Bubbles flares are sturdier and more reliable than single flares, but not more than double flares. They will not handle as much pressure as double flares and will likely fail before SAE.

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How To Single/Double/Bubble Flare A Brake Line?

Brake line flaring requires total concentration to ensure leak-proof connection without additional sealants. If that is not the case, you will lose the brake fluid, leading to brake failure. Fortunately, you can make a single, double, or bubble flare brake line yourself.

For flaring, you will need protective gear (rubber gloves and goggles), measuring tape, tubing cutter, brake line kit, and flaring tool. Proceed to the steps if you have assembled all the needed tools.

How To Make A Single Flare Brake Line

  1. Wear your protective gear. Measure the length of the brake line needed using a measuring tape.
  2. Cut the brake tubing using a tubing cutter according to the length measured in the previous step. You can use a hacksaw, but remember to file the burrs.
  3. Use the single flaring tool to create a single flare brake line. Do that by placing the cone over the end of the tubing and centering it.
  4. Turn the advance screw in the flaring tool until the flare of the appropriate size is formed. The number of turns needed depends on the size of the brake line flare you need. Check the manual for reference.
  5. Check the formed flare for any imperfections. If there are cracks or splits, discard the brake flare and start the procedure again.

How To Make A Bubble and Double Flare Brake Line

  • Measure the brake line length needed and cut the tubing as appropriate.
  • Use a flaring tool to clamp the tubing into the flaring bar. Ensure the depth is the same as the edge of the tubing size insert.
  • Install a yoke. Use it to move the cone into the tube to create a bell shape. What is formed is the bubble flare. Stop at this step if you are making a bubble flare brake line and inspect the result for defects.
  • Remove the insert and advance the cone into the bell to create a double flare brake line.
  • Unclamp the double flare brake line and inspect for any imperfections. If you spot a crack, redo the procedure.
A video about how to flare brake lines.

Best Single/Double/Bubble Flaring Tool Recommendation

1. Single and Double Flaring Tool Kit (2in1)

If you want to make perfect flare brake lines, this is all you need. You can use it to make any flare on copper, brass, aluminum, magnesium, or soft steel tubing. It has a set of 3/16-inch, 1/4-inch, 5/16-inch, 3/8-inch, 1/2-inch adapters for making flares of different sizes.

Thorstone Double & Single Flaring Tool Kit

Thorstone Double & Single Flaring Tool Kit

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2. Double/Single Flaring Tool Kit

This is a reliable, efficient, and effective flaring tool kit for making single or double brake line flares. It is specifically designed for durability. The friction that often causes wear on the swivel is significantly reduced. You can use it to make flares of different sizes on different tubing materials.

ARES 18019 – Double Flaring Tool Set

Double/Single Flaring Tool Kit

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3. Single, Double, Bubble Flaring Tool Kit (3in1)

It is a professional brake line flaring tool for making all three flare types. It is easy to mount on the workbench with a vise and has a handle screw to secure the adapter and tube. You can make perfect flares of different sizes in a single attempt.

TGR Professional Brake Line Flaring Tool

TGR Professional Brake Line Flaring Tool

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4. Bubble Flaring Tool Kit

Neiko is a specialized ISO/bubble flare-making toolkit. With it, you can make bubble flares for all European cars. It comes as a unit with a yoke assembly, flaring bar, gauge, and four adapters for making flares of different sizes.

Neiko 20657A ISO/Bubble Flaring Auto Tool Kit 

Neiko 20657A ISO/Bubble Flaring Auto Tool Kit

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5. Single Flaring Tool Kit

This is a 10-piece flaring and swaging toolkit for every professional mechanic. Apart from creating flares for the vehicle’s braking system, you can additionally use the kit for widening gas, water, and refrigeration piping. It comes with flaring adapters of all sizes you will ever need.

Flaring Tool Kit, Single Flaring and Swaging Tool

Flaring Tool Kit, Single Flaring and Swaging Tool with Extra Adapters

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FAQs

1. Saddle plugs vs. Double flare

A saddle plug is a type of double flare with smoothly tapered edges. The saddle plug is easier to insert and remove. And once it is inserted, it stays in. Its popularity increases day by day for its reliability.

2. Inverted Flare vs. Bubble Flare

Inverter flare is also called a double flare. It looks like an inverted funnel, while bubble flare appears like a button. Inverted flare is sturdier and more reliable than bubble flare.

3. Inverted Flare vs. Double Flare

Inverted flare is another name of double flare. Double flare brake lines are the most commonly found in American and Asian cars.

4. Can you do a bubble flare with a double flare tool?

Yes. Bubble flare is the first step to making a double flare brake line. If you can do the double flare, a bubble flare will not be a problem at all.

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