51 71 ... Removing and installing/replacing left/right reinforcement cover

Release bolt (1) on front assembly underside protection.

Release screws (3) and nuts (4).

Remove reinforcement cover (2).

Installation: 

Make sure reinforcement cover (2) is correctly seated.

Fig 1: Identifying Reinforcement Cover, Screws, Nut And Bolt

Courtesy of BMW OF NORTH AMERICA, INC.