Abstract: A bicycle disk brake assembly includes a pressure-reducing cylinder attached to a caliper body and formed with an inner chamber and outer chamber. Upon application of an external pressure to a hydraulic fluid, which is filled within a fluid reservoir in the caliper body, the fluid flows from the reservoir to the outer chamber. When the fluid pressure in the outer chamber reaches a first value, an inner check valve is operated so as to permit flow of the fluid from the outer chamber to the inner chamber. Thereafter, when the fluid pressure in the inner chamber reaches a second value and when the external pressure is released, a resilient member biases the fluid in the inner chamber to activate an outer check valve, thereby permitting flow of the fluid from the inner chamber to the outer chamber and subsequently to the reservoir.