Whether you are building a new project or just replacing some worn out parts, brake lines have long been a source of frustration for DIY mechanics. While it may seem that there is an art to bending metal lines, it is actually a very logical skill that anyone can learn. There are two processes that create headaches when making brake lines – flaring and bending. This article focuses on the task of bending brake lines and fuel lines. The level of complexity depends on the length of line you are working with and the chosen material. Short lines are much easier to work with than long lines. Regardless, the process is the same. So here’s what you need to know about bending brake lines.
Brake Line Types
When shopping for brake lines there are four types of hard line used for braking systems: steel, soft steel, stainless steel, and nickel-copper alloy. Each has it’s benefits and drawbacks.
Steel – The most common type of hard line is galvanized mild steel. This is what the factory uses for all of the brake lines. Steel is affordable, durable and easy to come by. The drawbacks are that steel rusts, and it is hard to bend. The rust is the biggest issue here. Brake fluid is extremely hygroscopic, meaning it absorbs water easily. Even though the system is sealed, there is still moisture available at the top of the reservoir that is open to the air. As the brake fluid ages, it becomes more and more saturated with water. Water and steel equals rust. The absence of may oxygen slow down the corrosion process, but not completely. This is what leads to ruined brake calipers and wheel cylinders. To fight this, the steel is galvanized to protect the surface. The issue of bending the brake lines can be overcome with bending tools, since steel tubing is not readily bent by hand.
Soft Steel – The more exotic tubing options are costly, whereas steel is cheap. Where regular steel lines are hard to bend and prone to rust, there is another solution – Poly-
Stainless Steel – For the ultimate in hard lines, stainless steel is the solution. Stainless steel lines are impervious to rust, so they last forever. Great, problem solved. Hold on there buddy, stainless lines have a few drawbacks – namely, the cost. Stainless steel lines are expensive, three to four times more than regular steel lines. Stainless steel hard lines are not too difficult to bend, but flaring them is. You need a really good flaring tool to make good quality double flares with stainless steel tubing. For show cars and street rods, the polished look of stainless steel is unmatched.
NiCopp® – In use since the 1970s, nickel-copper hard lines have the strength of steel, are rust proof, and easy to bend. Because the lines bend so easy, they can be snaked through the chassis easily. Made of 90-10 copper to nickel, NiCopp® lines are reasonably priced as well. The biggest drawback of NiCopp® lines are availability, as they may be hard to find locally.
Pre-Bent Or Bend It Yourself?
There are several ways to replace a bad hard line on your vehicle. You could order a pre-bent line from your local NAPA store, or you can bend one yourself. Pre-bent lines are great when the application is available and you just want to swap out the part and move on. Pre-bent lines are also available in different tubing materials. Unfortunately not every application has a pre-bent line available. There’s also custom work. For those that need to bend a line yourself, the best solution is Poly-Armour® sticks. These are pre-flared lines that come in different lengths, with varying sizes and types of fittings. Poly-
Tools For Bending Brake Lines
There are several types of tools available, from simple radius tools to more accurate lever-action benders. While there is an old trick using sand to bend lines by hand, there’s really no need when there are tools readily available on the market. The key to using a bending tool is to get a quality tool that won’t kink the line. While Poly-
Simple Bender – These tools are single piece and use a hook-type latch to lock the tubing in place. You use one hand to hold the line and tool together, while the other hand bends the line. These tools are fairly cheap but have a fairly high chance of ruining a piece of tubing. They don’t secure the line so complicated bends can easily become out of line, where your bends don’t match the direction they need to be. While they may help you get the job done in a pinch, this is not a good tool for bending tight bends on small line.
Lever-Action – This type of tool uses mechanical advantage to make bending lines easier. While the tubing can still rotate (allowing complex layouts become out of line), it is easier to manage with a lever-action bender. Lever-type benders typically have multiple diameter positions, and marking for varying degrees of bend. Most of these tools are designed for specific radius bends, there are tools for tight bends, tools for large bends. You can manipulate this to a degree by repositioning the line, making a larger radius, but you can’t make a smaller radius than the tool you have. Side note – the cheap version of lever-action benders that have an interchangeable die do not work very well, they will usually just kink your line.
Spring-Type – This is a very basic bender meant mainly for copper and aluminum tubing. There are two types, internal or external. Both prevent the tube from collapsing and kinking while hand bending. Best for gentle, large diameter bends.
Bending Brake Lines
Once you have the proper tools, you can get your parts ready. If you are replacing a line, then you should have the existing line to use as a reference. When picking a length of pre-flared brake line round up so you don’t end come up short on reaching your connection.
Start at one end, and re-create the line bend for bend. You can even add some tape as you go to keep the bends in line. If you are creating a new line without a reference, you should make a reference. Bailing wire works really well for this task. It stays bent, and you can use it just like you would an existing line. Plus it is really cheap and has a thousand other uses around the shop. You can also use a wire coat hanger that has been straighten out.
The most important factor that you need to keep in mind when bending brake lines- don’t forget the flares and fittings. Even seasoned pros sometimes to forget to slide the fitting all the way to the flare before bending the line, which means you have to either straighten the line or cut and reflare the line. You can always use a piece of tape to hold the fitting at the end of the line by the flare just in case. Also, when making bends near the end of the line, if you need to add a flare, do it BEFORE bending the line, your flare tool needs room ahead of the bend, make sure you have enough.
Bending brake lines is not difficult, but it does take a little practice to get good at it. If you really want to master this skills pick up a roll of brake line and spend some time worknig with it in various shapes. You’ll start to get an idea of what you can and can’t do with it. Whether you are plumbing in your brakes, a transmission cooler, or hardlining your air-ride system, bending tubing is required. With a little practice, you will be able to master the art of bending brake lines and fuel lines.
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A life-long gearhead, Jefferson Bryant spends more time in the shop than anywhere else. His career began in the car audio industry as a shop manager, eventually working his way into a position at Rockford Fosgate as a product designer. In 2003, he began writing tech articles for magazines, and has been working as an automotive journalist ever since. His work has been featured in Car Craft, Hot Rod, Rod & Custom, Truckin’, Mopar Muscle, and many more. Jefferson has also written 4 books and produced countless videos. Jefferson operates Red Dirt Rodz, his personal garage studio, where all of his magazine articles and tech videos are produced.