Factory flexible brake lines are typically of rubber hose construction and those lines are designed to last well over a decade for the average lifespan of a vehicle. However, when we modify our off-road rigs, we often install suspension lifts and larger, heavier tires. That means we may need longer brake lines or may have a desire to upgrade to stainless braided lines.
Stainless brake lines can be a great upgrade as the stiffer Teflon core inside the braided line swells less under hard braking (heat) so provides a more efficient and precise braking action when compared to standard OEM rubber hoses. However, there are a few considerations to keep in mind when changing to stainless lines.
Most lines contain the Teflon hose inner tube with protection layers over that, followed by the stainless braided layer, and sometimes a final vinyl cover over the braid. The Teflon is fairly fragile so needs the outer layers for strength and protection from debris and chaffing. Teflon tubing does not deteriorate over time, but can degrade if dirt works its way into the line such that it contacts the Teflon tubing and is allowed to abrade on this surface.
Stainless lines are available in a range of qualities and construction. All have the Teflon inner core that contains the pressurized brake fluid and a stainless braid layer. Some brands will add a Kevlar protective layer and/or additional laminating layers to further reinforce the hose and protect it from abrasion.
One way to add a little extra protection to a stainless braid hose is to cover it with plastic spiral wrap used for bundling electrical wiring. This is a prudent practice for lines that have no outer vinyl covering if the braid can rub and abrade on some nearby surface. It also provides an added protection against flying gravel as well.
Not all stainless braided lines are Department of Transportation approved for on-road use. Federal Motor Safety Standards define stringent tests and specific hose end construction to qualify a stainless hose as DOT-approved. Some braided lines can’t successfully pass a “whip” test that checks the ability of the end connection to flex and the hose not fail and leak pressure. Those that do pass these criteria should be tagged as such.
Often times when you lift a vehicle, you add longer stainless lines to accommodate more suspension travel. You’ll want to be careful how you route the longer lines and be wary of how they move as the suspension cycles to ensure they don’t get caught anywhere or kink in any way. On front live axle suspensions we sometimes attach a lightweight spring around a short length of split rubber hose slipped over the brake line to take up the slack of the braided hose as needed. When the axle droops, the spring can stretch to allow the hose to travel downward.