From Trackpedia
Brakes Lines
"Brake line" is a common term used in automobile talk. It is typically used when referring to any line in the braking system that contains brake fluid. Car enthusiasts exaggerate over braided stainless steel brake lines -- the steel-encased Teflon flexes considerably less than ordinary rubber hoses, making for a firmer pedal feel. But controversy surrounds the safety of braided stainless steel hoses, since they can fail if they're not replaced regularly and protected from debris. If braided stainless steel is in your future, buy from a reputable supplier, and look for lines that come with a polyurethane jacket to prevent chafing.
In most typical automobile and motorcycle systems the braking system is made up of both hard lines and soft lines.
Hard Lines
The hard line of a braking system is the solid aluminum lines that typically run the length of the car from the master cylinder to the wheel wells where they mate up with the soft lines that head to the caliper. Hard lines come in multiple shapes and sizes and typically can be bent easily with tube benders to fit any need you have. The main reason hard lines span the majority of the brake system is that hard lines being solid tubing do not flex or give thus allowing for good braking modulation and feel.
Soft Lines
The soft line of a braking system is the part of the brake line that runs from the wheel well to the brake caliper. The reason this part of the line needs to be flexible is that the line needs to be able to flex and move over the suspensions travel or turning wheels movement. Typically on most motor vehicles the soft line is a high strength rubber hose. On performance vehicles these lines are stainless steel wrapped hose.
Stainless steel brake lines improve pedal feel and reduce the amount of time between applied pedal pressure and actual deceleration by preventing expansion, which stock rubber flex lines allow. This provides a quicker pedal response, and allows the driver to maintain consistent brake pressure and precision brake modulation.
Manufacturers and Distributors of Stainless Steel Brake Lines
