What's Inside — Brake Lines

When you pull your brake lever can you hear the cries from the stock rubber hoses as they bulge and expand? They're practically begging to be replaced with something stronger.

Hydraulics aren't just for 1964 Impala low-riders-in fact, all modern motorcycles use hydraulic braking systems. The hydraulic fluid's function is pretty simple: Liquids don't compress, but they do create pressure, and the pressurized fluid pushes the pistons against the rotor to stop the bike.

If you consider the amount of pressure and force traveling through the brake line, it starts to make sense why a reinforced hose works better.

Pressure in the brake system is essentially equal all the time, but that means the aluminum master cylinder and calipers withstand the same pressure as a rubber bit of hose. You can easily identify the weakest link in the system-it's the one not made of a metal. This is why reinforced brake lines are important, because they need to be able to withstand the huge amounts of pressure created at the master cylinder and are used to push the pistons and pads against the rotors.

When the brake line can't control expansion (stock lines tend to bulge) the rider will lose brake performance from the loss of pressure. The translation from the bulging lines to the rider's hand travels via the lever.

There is a fine line, though, between eliminating this expansion and controlling it. Too much constriction would mean that the brake lever would become a virtual on/off switch with no feel at the lever whatsoever, while too much expansion would equate to very little stopping power.

The brake fluid is contained within a tube, but there's more than meets the eye. A typical brake line is made of three parts: an inner liner that holds the fluid (usually Teflon), followed by a layer of webbed mesh (for strength) and a rubber coating for protection.

The problem with this arrangement is in the stock hose's second layer. Fabric mesh controls the strength and flexibility but simply doesn't match up to an aftermarket (steel-braided) line's construction.

Most stock lines have a fiber reinforcement that, while under normal street-riding strain, is adequate. But after some serious riding with hard braking, however, the rubber hose begins to heat up (heat transfers from the rotors to the pads and fluid) and becomes pliable-allowing for more expansion and decreased braking power.

Steel-braided lines are designed similarly to the stock hoses, but instead of fabric webbing it's steel mesh. The stiffer substance greatly reduces the brake line's tendency to bulge and expand and offers much better braking performance.

Aftermarket brake lines work better and therefore offer more safety through more powerful and consistent braking power. Furthermore, the ability to customize with different color options makes a set of hoses money well spent.