The Bilstein B8 Performance Plus rear shock (manufacturer part 24-028295) is a gas-pressure monotube damper sized for the E39 5 Series and listed for the 2001 525i base sedan. The manufacturer positions the B8 Performance Plus as a performance lowering shock, tuned to complement lowered springs. Its monotube layout uses a floating piston to keep oil and gas apart, and the manufacturer says this construction sheds heat under hard use, so damping holds steadier on repeated spirited runs than a worn or overheated stock unit. Each unit is individually fine-tuned during road testing to balance firm, controlled handling against everyday comfort, which is the main reason to pick this over a generic budget damper.
If you have dropped your E39 on aftermarket springs and are still running factory-level damping, the rear end can feel bouncy and unsettled over mid-corner bumps. Matching a valved shock to the lowered ride height addresses that mismatch directly. Search terms that fit this part include 24-028295 rear shock, E39 525i lowering spring shock, B8 Performance Plus 525i sedan, and Bilstein sport rear shock E39. Before ordering, confirm your car's chassis and suspension options against the manufacturer's application guide. Rear shock replacement on this chassis is a moderate weekend job that involves removing the rear seat and parcel shelf, so plan for a few hours per side and have a second person available to help manage the spring and shock assembly.
The manufacturer designs the B8 Performance Plus to enhance a lowered suspension and positions it for use with lowering springs. If your car still has factory-height springs, confirm the correct Bilstein line for your setup with the manufacturer before installing.
Owners on user forums describe removing the rear seat, the parcel shelf, and the rear speakers to reach the upper shock mounts. Owners of related E39 models report that the lower mounts and the sway bar may need to be disconnected, which adds time to the job.
Owners on user forums report that rear shock replacement on the E39 is manageable for a home mechanic with a standard socket set, though it is not a quick job. Access requires removing the rear seat cushion and back, the parcel tray, and the rear speaker and trim pieces, after which the upper shock nuts become visible. Plan for 21mm and 22mm sockets, a 1/2-inch impact wrench, and a jack with a urethane pad placed on a solid point of the rear axle. Owners recommend replacing the top shock tower nuts and using thread locker on the new hardware. Shop towels and a cleaning agent help when removing seized fasteners. Working on both sides usually takes most of an afternoon, so doing one side at a time keeps the other side's reference geometry available.
