A bumper assembly for attachment to a post has a hollow bumper member with an internal bore that fits over a post and allows the bumper member to rotate. A protective liner is provided between the bumper member and the post and has an internal bore that fits around the post and an external wear surface that fits within and rotatably supports the bumper member. A retaining ring can be secured to the post to hold the bumper assembly in place vertically. Alternatively, the hollow bumper member can be provided with end faces that interact with the upper and lower surfaces of a protective liner positioned within the hollow bumper member to hold the bumper assembly in place vertically. The components of the bumper assembly can be split along one side or provided as two separate halves attachable together to facilitate attachment to posts that are restrained on both ends.