A bicycle brake hose is the component that connects and transfers the power from your brake lever on the handlebars to your caliper down at the wheel. Bicycle brake hoses come in different lengths and designs depending on whether you need them for a DOT system or a mineral oil brake system. Check your brake hoses regularly for leaks or damage. If you notice that your brake levers can be pushed all the way into the handlebars, it may be your brake hose that is damaged or dried out, and leaking brake fluid / oil.