Brake lines can be made from a variety of different materials, but one of the most popular materials among off-roaders and performance drivers is steel. There are a couple of advantages to steel:
First, for serious off-road drivers, puncturing a brake line is always a concern. With soft brake lines, a rock or twig could easily make a small puncture in a brake line that could end up being catastrophic. A second advantage is that steel brake lines don't swell the way a flexible line might. With repeated use, a flexible brake line can stretch from the pressure of the fluid running through it. This is called brake line swelling. It may not seem like a big deal, but once the line is stretched, the line pressure lessens, which weakens braking performance. Over time, this decrease in braking performance will only become more if a problem. In a panic situation, you definitely don't want swollen lines. Steel brake lines can't swell and your brakes' performance will remain strong.
Steel brake lines may be strong, but they aren't perfect. They're subject to corrosion and breakage just like other brake parts on your vehicle. Steel lines are also less flexible than other types of brake lines, so their connections to each brake part in the system should be checked more often.
On the next page we'll learn about braided steel lines.