Brake Lines, Fittings, & Hoses

Brake Line Fitting Types Explained

The main brake line fitting types are inverted double flare, bubble flare, AN, banjo, and compression. Each one seals differently, so match the fitting to the flare on your tubing and the port on your component before you order.

Here's how the common brake line fittings compare:

• Inverted double flares fold a 45-degree flare over itself for a strong metal-to-metal seal.
• Bubble flares, also called ISO flares, form a rounded end used on many metric systems.
• AN fittings use a 37-degree single flare, a sleeve, and a B-nut, and they're common in race plumbing.
• Banjo fittings pass a hollow bolt through a round eye and seal with crush washers at the caliper.
• Compression fittings squeeze a ferrule onto the tube and are generally avoided on hydraulic brake lines.

Flaring your own tubing? Learn how to flare a brake line for both 37-degree single flares and 45-degree double flares before you cut. Then browse our other brake system parts to finish the job.

How to Choose the Right Brake Line Fitting Size

Choose your fitting by tubing diameter first, then thread size and flare type. You'll find 3/16" tubing on many cars and hot rods. 1/4" and 3/8" lines appear on many trucks, older vehicles, and some master cylinder outlets.

Most 3/16 brake line fittings use 3/8"-24 inverted flare threads. 1/4 brake line fittings commonly use 7/16" threads in either -24 or -20 pitch, so check yours with a thread gauge before you buy.

Metric brake line fittings, such as 10mm x 1.0, are common on imports and many late-model vehicles. They won't thread correctly into SAE ports, and forcing a near-match can strip the port or leave a joint that weeps under pressure.

Replacing a full run? Shop brake lines in the tubing size you need, and compare plumbing options from Russell Performance. Measuring twice here saves you a second order and a second bleed.

Brake Line Fitting Adapters, Unions, and Tees

A brake line fitting adapter converts one thread or flare style to another. A brake line union joins two lines, and a tee splits one line into two. You'll use at least one of these on most custom brake builds.

Adapters let you connect AN brake fittings to factory-style ports. Earl's Performance Plumbing offers -3AN male to 10mm x 1.0 male adapters, plus -4AN male adapters to 3/8"-24 and 7/16"-20 male inverted flare. Earl's also makes brake banjo fittings and brake line T-fittings with 3/8"-24 inverted flare ports.

Unions help when you're repairing a damaged section or joining a new run to an existing line. Use matching flare types and threads on both ends unless you specifically need an adapter.

For more AN and hard-line pieces, check fittings from Vibrant Performance. If you're starting from scratch, a brake line fitting kit puts common sizes in one order, so you're not stuck mid-job waiting on one nut.

Steel Brake Lines vs. Braided Stainless Brake Hoses

Use rigid steel lines for fixed runs along the frame and flexible hoses wherever the suspension or steering moves. Braided stainless brake hoses wrap an inner hose in stainless braid, which helps limit expansion under pressure for a firmer pedal.

Shop brake hoses including Earl's Speed-Flex lines and extension hoses, plus coated -3AN brake line hose from Allstar Performance. A coating adds a protective layer that helps shield the braid and nearby parts from abrasion.

Route every flex line so it clears tires, springs, and exhaust at full lock and full droop. Secure it with stainless flex hose C clips and other brake hose hardware so it can't rub through.

Rubber hoses age even when they look fine on the outside. Before you reuse old ones, read up on how long brake hoses last and the symptoms that signal it's time to replace them.

Hardware, Clips, and Bleeders That Complete the System

Clips, brackets, and bleeders finish your brake plumbing by keeping lines secure and air out. Skip them, and even perfect flares can fail early.

Loose tubing vibrates, and that movement fatigues the line right at the flare. Browse brake line hardware for clips and mounting pieces sized to your tubing, and plan your mounting points as carefully as your fittings. Space clips evenly along long runs, and keep tubing away from sharp edges and heat.

Any time you open the system, you'll need to bleed it, starting at the wheel farthest from the master cylinder on most setups. Our brake bleeders and hardware selection covers bleeder screws and related pieces that make the job cleaner.

Running calipers from Wilwood? Follow our guide on how to bleed a Wilwood brake system to purge trapped air. Then check every fitting for seepage and test the pedal at low speed before you drive hard.