The brake cylinder is one of the important components in the entire vehicle braking process. Its performance is directly related to the braking force of the whole vehicle. Therefore, the quality of the braking performance cannot be ignored. The brake cylinder is a vulnerable part. The principle is very simple. The push rod and leather cup inside the brake cylinder are structures that are often easily damaged. The direct result of this is that the cylinder leaks air during braking, the brake fails to work, and the use of inferior products will not only increase the cost of maintenance in the later period. It will also affect the coordination of the main trailer vehicle braking, resulting in the occurrence of potential safety hazards. Although the price of the brand air chamber sub-pump is more expensive, the service life and reliability are much higher than those of the cottage products.