How-to Create & Flare Brake Lines

Fabricating, routing and plumbing your vehicle for hydraulic brake, transmission and fuel lines is not a complicated task, and in many ways is very enjoyable. If the body is removed from the chassis, the task is much easier; however, with patience, the entire hydraulic system can be replaced while the vehicle remains completely assembled. Even if you're replacing only one or two lines on your project vehicle, or repairing corrosion damage on a daily driver, you can purchase the tools and lines you need less expensively than taking the car back to the dealer or mechanic. In this article we will focus on the brake lines only.

DIY Brake Tool Kit:

Double/Single Tubing Flaring Kit

Triple-Head Tubing Bender

Brake Line Kits

How to replace individual lines:

1. Remove the existing line and plug the line upstream to eliminate brake fluid from leaking and emptying the master cylinder. Our Vinyl Plug Kit is perfect for this. We have an assortment of sizes that can be placed over the end of the line, fitting or flare and held in place with duct tape (another use for the stuff!).

2. Now take the damaged line to the work bench. Use the new line from the kit and the Triple-Head Tubing Bender to form the line to match the original.

3. Once you have the basic shape and length laid out, it's time to flare the ends. Most important on this step is to use a tubing cutter. If you're bent on not using one, at least make sure to use a fine-tooth (24-tooth blade minimum) hack saw and slowly cut the line. You do not want to put pressure on the saw, or you will deform the line.

4. Once cut, use a metal file to square the ends; then you must clean-up the inside diameter of the line. Again, the tubing cutter has a small metal tool for this job, but if you do not have one, use a tapered reamer to remove the burr inside the tubing—it must be removed!

5. Slip on the appropriate fitting (with the threaded end toward the end you just cut) and install the line in the appropriate die for the flaring tool (this is the Professional Brake Tubing Flaring Tool). From here forward, the instructions for the flaring kit should be followed; make sure to lubricate the flaring die and tubing with anti-seize or brake fluid.

6. Once the flare is created, move on to the other end and repeat. Look closely at the formed flare for any signs of cracking or distortion.

7. If the flare looks good, blow air through the line to remove any contaminants, or flush with our PRE Painting Prep. Use the aerosol can to blow PRE through the line to flush any metal shavings out.

Don't be discouraged if your flare isn't quite perfect at first. After several more practice tries with the pre-cut sections, you WILL be creating perfect flares worth boasting about! With confidence, you're now ready to create a replacement brake line complete with all factory bends. If you take your time and are accurate with the tube-end preparation, the flares will be equivalent to OE. Once all the lines are formed you can install them per manufacturer's routing and torques, using tape on the fittings and flare wrenches, and bleed the system. This is also how easy it is to make brake, transmission or fuel lines.

If you're going to re-plumb your entire project vehicle with all-new OE or stainless lines, we suggest purchasing the tools below and get ready for a truly enjoyable, professional, and rewarding experience. The tools listed below will form perfect, crack-free 45° double-flares in seconds. You can rest assured that the flares will not fail. You're going to be flaring 10-12 critical tube ends, so do not risk safety with a tool from an off-shore company. Since your life depends on it, buy the best quality! Even with all these pro quality tools, it's still less expensive than buying pre-formed kits.

Professional Brake Tool Kit:

Professional Brake Tubing Flaring Tool
Tubing Bender and Forming Pliers Kit
Brake Line Kits

Re-plumbing the entire vehicle is very straightforward and easy. Just start with the rear wheel cylinders or calipers, and work forward to the proportion valve or master cylinder. Once completed, begin with the front wheels, fuel and transmission lines. If you break the vehicle up into sections or quadrants, it is very easy to form accurate, professional lines, and leak-free flares.

Follow the overview steps above with each of the lines, and remember to clean the lines before installation.

Additional tech tips:

Use 1/8"-dia. steel rod available at home centers to layout the line and routing. Once you have the pattern, you can then bend and form the brake line to duplicate the 1/8"-dia. rod.

Watch where you route the new lines. Do not route under frame, as jacks and lifts will crush the lines. Make sure to watch around suspension components and take into consideration their movement and possible contact with your line.

Chaffing, vibration and flexing are the enemy of rigid lines. Take into consideration these forces when routing the lines, and clamp to the frame every 24" if possible.

Minimum bend radius "rule of thumb": For 3/16" line, it's 4" in dia.; for 1/4" line, it's 6-1/2" in dia.

Always run fuel lines under electrical lines. In the event the fuel line leaks, it won't drip onto a live electrical line or circuit.

Never let the master cylinder run dry when bleeding brakes. If this happens, you'll have to bench-bleed the master cylinder. This is not hard, but it is time-consuming and requires you to re-do what you've just done.

Flex Joints are intentional "circles" formed in the lines to allow movement between two components without cold-working or cracking the line. As you know, if the fluid leaks out of the brake lines, you'll have to use the front end sheet metal to slow the car.

Forming odd curves or circles. The use of our Triple-Head Tubing Bender is a must when forming brake lines; you'll inevitably run into shapes that you must improvise on. Use wooden dowels, metal tubing or exhaust tubing to form circles.

Flaring and fittings. DO NOT EVER use cheap or re-claimed fittings. Use only high-quality new fittings—they cost almost nothing and will save your life or your passenger's. DO NOT skimp here! Save a few dollars when it comes to carpet underlayment! Photo #2 is a shot of the fitting included in our lines kits. They are high-quality OE metal or stainless steel and look great.

Once you have formed your lines, adjustments may be necessary. Use the Brake Line Forming Tool Pliers to gently "nudge" the lines into perfect alignment

Double flare vs. single flare. The double flare is stronger and better at sealing than the traditional single flare. Always use the double flare connection where possible.

AN fittings: "AN" or "Army/Navy" (which is what the abbreviation stands for) are 37° flares where automotive has 45° standard flares. These CANNOT be intermixed, and it doesn't matter how cool you think they will look. If the caliper or wheel cylinder is not machined to accept the 37° flare, THEY WILL LEAK! The reason the military went to AN-37° plumbing was to keep standard automotive product from ending up on aircraft.

Lastly, measure twice and cut once. That saying has nothing to do with this article, but you can rephrase it as "check twice and bend only once". You do not want to continually bend and re-bend the same area. This will weaken the tubing and possibly create a potential failure spot down the road.

Get out there and build something cool!