Rubber and Stainless Steel Brake Lines Compared

Rubber and Stainless Steel Brake Lines Compared

Last Updated August 8, 2023 | Meghan Drummond

Even though they’re arguably one of the most essential parts of your vehicle, few people take the time to really think about their brake lines (unless they aren’t working). Brake lines are wholly ignorable provided they continue to function correctly, but if you’re increasing your vehicle’s ability to take off, then it’s not a bad idea to improve its ability to stop accordingly.

How Brake Lines Function

A simple diagram shows the exchange of pressure needed for braking

In a hydraulic brake system, when you press down on your brake pedal, it sends brake fluid from the master cylinder down to the caliper, which presses against a brake pad, which presses against a brake disc, which is able to stop your car. This feels easier than it actually is because of power brakes, which use a vacuum modulator to multiply the force that the brake pedal is actually able to apply.

As you might imagine, the brake line is fairly important then, since without it you would have no way to communicate with the brakes on your vehicle.

Flexible and Hard Brake Lines

Brake lines are usually comprised of two parts: The first is a rigid hardline best thought of as a “brake pipe.” These need to be kept free of corrosion and typically come in either stainless steel or steel. Stainless steel offers some additional rust protection while steel is used to preserve a “factory-fresh” look for resto-mods.

The second part of the brake line is a flexible hose. This part has substantially more variety and is more likely to cause trouble. Because it’s required to be flexible, it can suffer from issues that the rigid brake lines really don’t encounter.

Thanks to the flexible portion of the brake line though, your car is able to have suspension travel, side to side movement, and all of the things that make driving fun. It also takes the brunt of the work away from the hardline, so that when it’s time for a brake line replacement you’re only replacing the small flexible portion of the line, as opposed to the whole thing.

In a typical OEM setup you’ll have a steel brake pipe feeding into a rubber brake hose, and while there are advantages to that system, there are also alternatives that may be better suited to some drivers.

Diagram showing hard brake line and flexible brake line connecting

Rubber Brake Lines

Rubber brake lines are surprisingly good. Though saying “rubber hose” makes it sound flimsy, the truth is they’re significantly more advanced. Rubber brake lines will be composed of EPDM rubber, which is then applied in layers to create a dense hose that’s tough enough to take a beating.

Though rubber is an inexpensive material, it’s also a high-quality one, and it lends itself to brake line purposes splendidly. Rubber deals with temperature shifts, environmental conditions, and movement incredibly well. For the average driver, rubber lines are fantastic, but unfortunately, for performance drivers, rubber isn’t a perfect solution.

Rubber’s greatest strength is also its greatest weakness. Over time, rubber tends to stretch, which leads to a lack of responsiveness. Because this happens over an extended period of time, most drivers are able to adjust their brake times accordingly and it’s not a huge issue. It also is a very slow process. Rubber brake hoses are very firm when they come straight from the factory, and they tend to hold up fairly well.

Over time though, people notice that their brakes start to feel “mushy.”

Two rubber brake line cross sections, one new and one old

Stainless Steel Lines

Not surprisingly, stainless steel lines are more resilient. The stainless steel that is used to replace the flexible portion of the brake line is comprised of braided stainless steel fibers to maintain flexibility (as opposed to the more solid stainless steel brake pipes). Some of these lines also incorporate other materials, like Kevlar.

Brake lines made out of stainless steel also don’t stretch out over time, so brake response stays as sensitive over time as they are on day one. Stainless steel (with or without kevlar) is also just a much tougher material than rubber, and more resistant to tears which can be caused by loose rocks or other debris. This makes stainless steel brake lines a great choice for off-roaders in addition to anyone who prefers an incredibly responsive brake.

Unfortunately, stainless steel lines have some downsides as well. They are more resistant, sure, but nothing is ever completely resistant, and finding a tear on a stainless steel line is much more difficult than it is on a rubber one. Many stainless steel brake lines have a PVC coating that needs to be maintained in order to prevent leaks.

Several lengths of stainless steel brake line

Are Stainless Steel Brake Lines Worth It?

Ultimately, whether or not stainless steel brake lines are worth the added cost depends on you and your driving style. If you’re an off-roader who is worried about debris severing your brake line, then they’re probably a good investment. Likewise, if you’re a performance driver who likes to barely press their brake before getting pushback and response, then it will certainly improve your braking experience.

If you are the type of person who jams their pedals straight to the floor anyway and could care less if they were made of putty or a firm rock, then you probably won’t see any substantial benefit from upgrading your brake lines. Also, if you are this type of driver, it might do you well to learn about how to engine brake in order to better take care of your vehicle.

There’s nothing inherently “wrong” with rubber brake lines, and they’re a great fit for the vast majority of drivers, but if you’re looking for a more responsive brake feel, then stainless steel brake lines are a great way to do that.

There are other ways to improve your brake feel as well, including improved brake pads or calipers. You can improve your brakes with any one of these upgrades or go all out and use them together. When it comes to brakes, "better safe than sorry" is a good policy.

Sources: Steel vs Rubber Brake Lines- Are Stainless Steel Lines Silly?, Engineering Explained | DIY Auto Service: How Hydraulic Brake Systems Work, Axle Addict | How Brake Lines Work, How Stuff Works | Image Credit: Car ID | One Man and His Mustang | Car Parts

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