12K-15K Hydraulic Trailer Brake Assembly – Left Hand

Description

The 12K – 15K hydraulic trailer brake assembly (left hand), part #31-B1212H-1, delivers strong and consistent hydraulic stopping power for heavy-duty trailer applications. This left-hand (driver side) unit fits 12,000 lb (12K) trailer axles and uses a 12.25″ x 5″ drum and shoe configuration designed for serious towing in equipment, construction, agricultural, and commercial fleet environments. The duo-servo hydraulic system increases brake force as the shoes engage, which gives operators confident braking performance under heavy load.

This assembly bolts to a 7-bolt brake flange and installs as a direct hydraulic replacement for common Dexter-style 12-1/4″ x 5″ LH trailer brake assemblies, as well as other OEM axle brands that use the same configuration. The integrated free-backing feature allows trailers to roll backward freely without dragging or locking the brake shoes, which protects the friction surfaces during yard moves, trailer staging, and tight jobsite maneuvering.

The 31-B1212H-1 comes pre-assembled with the hydraulic wheel cylinder, bonded brake shoes, return springs, and duo-servo hardware already installed. Dealers, fleet shops, and repair centers choose this format because it reduces service time and keeps high-value trailers on the road instead of sitting in the shop.

For best results, break in (burnish) the new brake assembly immediately after installation. Tow the trailer in a controlled area and apply repeated moderate braking cycles from a steady speed. Avoid hard panic stops during the first burnish period. This process seats the shoe linings to the drum surface and delivers consistent hydraulic braking performance under real load conditions.

Operators who demand dependable heavy-duty trailer brakes rely on this 12K hydraulic left-hand brake assembly for durability, compatibility with Dexter, smooth hydraulic modulation, and simple serviceability. Part #31-B1212H-1 makes an ideal upgrade or replacement for trailers whose brakes are in need of a fresh set of shoes.

12K – 15K hydraulic trailer brake additional part #: BK-12KH-01,1215HYDLHBRKAS, 77-1212H-1, K23-408-00