The axle hub is filled with grease until the grease forces the Bearing Buddy® piston outward about 1/8 inch.
Because the piston is spring loaded, the piston exerts a slight (3 psi) pressure against the grease, which maintains a slight pressure between the inside of the hub and the outside environment.
When the hub is submerged, water cannot enter the hub because of this pressure.
An automatic pressure relief feature prevents over-filling and over pressurization. Bearing Buddy diagram Without this feature, the inner seal will be damaged.
Grease can be added to the hub through an easily accessible grease fitting located in the center of the piston. Lubricant level (and pressure) can be checked quickly by pressing on the edge of the moveable piston. If you can rock or move the piston, the hub is properly filled. Bearing Buddy® will last the life of your trailer. The outer barrel is made of steel and is triple chrome plated. Internal Bearing Buddy® parts are made of stainless steel. Bearing Buddy® is also available with a stainless steel barrel for maximum corrosion protection.