Measuring and cutting brake lines before flaring or installation ensures you have an exact fit for your braking system and helps eliminate the risk of cutting your brake line too short, rendering it useless. In some instances, you may be able to bend the brake lines before cutting, but in either case, knowing your exact measurements can help you make a correct cut to reduce the chances of wasted or unusable brake lines. The steps below outline how to use the right tools to properly cut a brake line before flaring.
Step 1: Measure the Replacement Brake Line
Be sure to get a precise measurement if this is a replacement piece of brake line so that your cut is in exactly the right place. We are using a shoelace to measure, but a cloth tape measure will also work for longer sections. Starting at one end of the brake line, you will need to run this string as closely as possible to the brake line to account for each curve. If you’re going to be flaring the line, the flare will use the last quarter inch of line, so be sure to account for this in your overall measurement. Using a brass union fitting to link two pieces of brake line also requires you to subtract the length of the fitting from the length of line you’re cutting. Whatever you do, don’t cut your line too short – you can also trim off more of the line if necessary.
Step 2: Start to Cut the Brake Line Using a Tubing Cutter
Once the tubing cutter is in place on the line, turn the knob until the blade just makes contact with the brake line, and then another quarter turn. You can then turn the tubing cutter all the way around the brake line to lightly score it and ensure the line it leaves behind is straight. If you’re satisfied with your test cut, you can begin cutting through the brake line. Turn the tubing cutter knob a quarter to a half a turn at a time, or until it is tight, and then rotate the tubing cutter 360° clockwise, then counter-clockwise, around the brake line. Continue to tighten the knob every time you do this until you are nearly through the brake line.
Step 3: Slowly Finish Cutting the Brake Line
When you get close to completing the cut, go slower to make the cut as clean as possible. The tube needs to be smooth inside and out before attempting to flare it. If there’s a place on the new end of the line that isn’t smooth, and if you have enough brake line material left, it may be worth the time to make a smoother cut.
Step 4: File the Brake Line
Any time you cut the brake line, you’ll need to use a metal file to take the burrs off the cut end. Once the burrs have been removed, you will also want to file the line to a slight chamfer, or angle, around the opening so it can be properly flared.
Flaring a brake line means creating a tight seal between the brake fitting and brake line by using a brake flaring tool, adapter, and anvil to eliminate fluid leaks at the connections of the braking system. The flare is pressed against the sealing surface of any brake component or fitting by the flare nut, and its conical shape is designed to create a seal between the line and the component. It’s critical to correctly flare a brake line to be certain there are no leaks around the flare nut or line junction. These issues could cause a loss of hydraulic pressure and diminished brake performance, which can put you and others in danger. Read on to learn how to properly flare a brake line using a flaring tool. There are two types of flares that can be made with a flaring tool: single flares and double flares. All brake lines should be double-flared to withstand the high pressures of the brake system, so the rest of these steps will indicate how to make a double-flared brake line connection.
Step 1: Prepare to Flare Your Brake Line
To start this process, make sure that the line end is cut square and that it’s deburred and chamfered. If the new end and flare isn’t made properly, the brake line will not seal and you could have a leak. If you’ve never flared a brake line before, practice on a piece of spare brake line to make sure you know how to make a flare correctly.
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Do It Right: Make sure you have the correct size of flare nut in place in the right orientation before flaring, since you won’t be able to install the nuts once the line has been flared. |
Step 2: Place the Line in the Flaring Tool
Place the line in the correct hole of the flaring tool, leaving a small length of the tubing exposed. The length of exposed tubing should be equal to the height of the adapter you will be using. This length is very important to get a good flare. After determining the appropriate length, tighten the flaring bar firmly, starting with the nut closest to the tubing.
Step 3: Fit the Adapter Stem in the Tubing
Fit the adapter stem into the end of the tubing. The adapter is specific to the size of your brake line, so it should be snug when inserted into the tubing.
Step 4: Tighten the Anvil over the Adapter and Tube
Place the anvil over the adapter and turn it down until the adapter contacts the flaring bar, then remove the anvil and adapter. The end of the tubing should now be bell-shaped. Now, place the anvil over the bar and turn the anvil down into the end of the line until the tubing folds in on itself.
Remove the tool and inspect the tubing. It should be double-flared.
Step 5: Compare Your Brake Lines
Compare your flare with the end of a piece of brake line that was flared from the factory. They should look identical. The flared opening should be smooth all the way around and rolled evenly. If the flare doesn’t look right, do not install the brake line.
Bending brake lines is the process of contouring your new brake lines to fit the shape of your vehicle’s frame, axles, and suspension components. Bending brake lines also helps to prevent interference or contact with parts on the frame or in the engine compartment that could cause abrasions and eventual brake line failure. While copper or copper-nickel brake lines are designed to be bent and adjusted by hand, steel brake lines must be bent using special tools to ensure proper fitment and prevent kinking. By manually bending and adjusting your brake lines, you can build a brake line that matches the original, simplifies installation, and prevents future breakage, cracking, or deterioration of the brake line itself. All you need is a manual tubing bender to make an exact-fit replacement brake line, but it may be beneficial to practice with your brake line material to understand how bends are made and its tolerance for kinking before getting started on your final product.
Step 1: Position Your Brake Line in the Bending Tool
Slide your bending tool into place on your brake line.
Step 2: Bend the Brake Line
Start at one end and match each bend in the line you’re replacing. Take your time and work precisely. You want this piece of line to be shaped in exactly the same way as the one you removed.
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Do It Right: By situating the brake line in the same orientation as the old one, you can follow the bends more easily to ensure it won’t be too close to the exhaust or any moving parts. |
Step 3: Ensure the Brake Lines are Identical
Compare the new brake line to the one you removed from your vehicle to ensure they are identical. Provided your bends are in the correct place and you have proper flares and flare nuts on both ends, you should be ready to install your new brake line, bleed the brake system, and get your vehicle safely back on the road. Always be sure to check for leaks after installing a new brake line or other brake components, as any leak from the brake system is dangerous and should be repaired immediately.
Your brakes are one of the most important safety components in your vehicle — which is why maintaining, servicing, or repairing your brakes is a common and necessary car maintenance task. If you’re not confident performing these repairs yourself, we are happy to recommend a professional shop near you to get the job done right. If you’d like to tackle a brake repair yourself, discover brake-related articles in our How-To Hub to help simplify your next brake system project. Need a specialized brake tool that you will only use once? Check out our Loaner Tool Program, where you can rent the brake tools you need with only a refundable deposit required. For a complete brake system repair, turn to O’Reilly Auto Parts for the tools, resources, and replacement components to help you get the job done right the first time.