Fox may be working on one of the most exciting brake innovations of recent years. A U.S. patent application describes a brake lever with integrated air management designed to systematically remove air bubbles from the system, thereby ensuring a consistent brake feel.

The application, titled "Air Purging Disc Brake Master Cylinder Assembly," was filed in September 2024 and published in March 2026. In it, Fox describes a novel master cylinder designed to controlledly vent air accumulations in the reservoir area. The basic principle sounds simple: air bubbles rise to the highest point in the reservoir, where they can be removed from the system via a designated vent path. At the same time, a flexible membrane is designed to prevent new air from entering the hydraulic circuit. So far, there are no concrete images available; the image used here was generated by artificial intelligence.

According to the description, the patent application is not limited to the standard bleeding process. Fox explicitly mentions situations such as bike transport, extended storage, or temperature fluctuations. It is precisely under such conditions that air bubbles can accumulate in the system and, over time, lead to a spongy brake pedal feel. Should the technology make its way into series production, it could alleviate a problem with hydraulic disc brakes. This is because even high-quality systems lose performance over time if air enters the system or accumulates in the area of the master cylinder.

Whether and when the technology will hit the market remains to be seen. The publication of a patent application does not mean that a series product will result from it. The document shows that Fox is working intensively on new solutions for improved braking performance and a consistently stable pressure point. Fox already has experience with bleed systems in suspension forks. 

Incidentally, there has already been a dispute regarding bleed systems: In July 2022, Fox sued RockShox’s parent company, SRAM, in the U.S. for patent infringement. Fox accused its competitor of copying the bleed valves on the new RockShox suspension forks from them. The U.S. Patent and Trademark Office intervened and invalidated Fox’s key patent claims in June 2025.