Complete list of brake line fitting sizes

How to buy a new brake line fitting

Any auto parts store can help you match up your old rounded-over brake line fitting with a new one. But that assumes you manged to get the old one off and can get to the parts store. However, if you need to find the fitting yourself, this article will show you how to find the right fitting.

Here’s how to measure your current fitting

Brake fittings are classified first by the type of flare; either inverted, bubble or DIN. Next, there’s the brake line diameter, the threaded diameter, and thread count (thread pitch).

To measure thread count you’ll need a thread pitch gauge like this:

For SAE applications you’ll be measuring threads per inch. For metric applications, you’ll be measuring threads per millimeter.

Most domestic and Asian brands use an  inverted or bubble flare on the brake line ends

See the images below for the differences in brake line fitting flare types

The two most common brake line sizes for cars, light trucks and SUVs

Most cars and light-duty SUVS and CUVs use 3/16″ diameter brake line. Larger trucks often use 1/4″ lines.

If you look at the open end of these fittings, you’ll see the opening is tapered to match an inverted flare brake line

©, 202 Rick Muscoplat