How to find what type of flare is on your brake line

How to find out what flare is on your brake line

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How to identify what flare is on a brake line

How do I tell what kind of flare is on the end of my brake line?

There are two basic types of flares used on OEM automotive brake systems throughout the world. The SAE/double (inverted/45degree) flare and the DIN/ISO bubble flare. We will refer to them as SAE or DIN flare. The most common is the SAE flare. Typically found on all American and Asian cars, but the European style DIN flare is appearing everywhere now.

Never use a single flare on automotive components. The SAE/double flare standard is remarkably tolerant of production variations, but the assemblies must be the same standard. Single flares are never allowed on steel brake lines.

SAE/double flare

SAE/Double Flare

If it looks like a tiny funnel going into the ID of the tubing and the back side of the flare is at a 45 degree angle it is the SAE flare.

Pictured to the left is an A1-3 3/8 x 24 UNF common American/SAE nut with SAE flare (45 degree inverted/double) on 3/16"/4.75MM dia. brake line

DIN/ISO flare

DIN/ISO Bubble Flare

If the end of the tubing looks like a button and the back side angle of the flare is 90 degrees it is the DIN flare. You must use a nut with a "lead" for the DIN flare.

M1-3 10mm x 1.0 common European/DIN nut with DIN flare (ISO/bubble) on 3/16"/4.75MM dia. brake line.

How to find the flare of a brake line wothout the brake line

How do I tell what kind of flare I need if I don't have the brake lines? (Part 1)

Look in the port where the line goes. If the bottom looks like a volcano pointing up at you it is an SAE flare seat.

Pictured to the left is an SAE flare seat (45 degree inverted/double) on a UA1-3br union

How to find the flare of a brake line wothout the brake line

How do I tell what kind of flare I need if I don't have the brake lines? (Part 2)

Look in the port where the line goes. If it looks funnel shaped going away from you it is a DIN flare seat.

Pictured to the left is a DIN flare seat (ISO/bubble) on a UM14-3 union

Brake line port with nothing in it

What if there is nothing in the bottom of the port?

On line locks, adjustable brake bias valves, etc. you sometimes will find no seat but a hole with a pipe thread in it. You will need an adaptor. You can adapt it to an SAE seat with our part number AD1br, but I recommend using our 37 degree adaptor, AN816-3. (Pictured on the left) We do not have DIN or metric SAE adaptors.

37 degree flares

What is a 37 degree flare?

If you are fitting aftermarket/high performance parts you may run into 37 degree flares. The 37 degree flare was standardized as A.N. (Army/Navy) during WWII for aircraft use.AN/37 degree nuts and fittings accept single and double flares. It is acceptable practice to single flare Cuniferâ„¢ (seamless) brake line for use with AN/37 degree fittings. Never single flare steel brake line.

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