The Papa-Bravo E89 rear brake kit uses standard BMW components with a custom designed bracket to create a significant upgrade to the rear brake capability as measured in available braking force, resistance to fade and reduced wear rates of both discs and pads.

They are primarily focused on road based E89s that have had a front BBK upgrade (E90/F series/Mustang/Alcon etc).

The forces generated by the PB BBKs are well within the limits of the ABS and stability control systems.

There are two kits, they both use the same caliper and caliper cradles but differ in the size of the discs, either 345 x 24 mm or 370 x 24 mm.

The Z4 E89 18i/20i/23i/28i/30i/35i US version all have a 300 x 20 rear disc and the 35i European and 35is have a 324 x 20 rear disc.

Caliper part numbers (F10 5 series) are BMW (34 21 6 793 048) BMW (6 793 048) and BMW (34 21 6 793 047)BMW (6 793 047).

The caliper cradle part numbers are BMW (34 21 6 793 053) BMW (6 793 053) and BMW (34 21 6 793 053) BMW (6 793 053).

The 5 series calipers use exactly the same electronic parking brake motor as found on the E89 and hence the normal EPB capabilities are retained including parking brake and emergency brake activation. No programming or  coding required.

The 345mm kit uses a E60 5 Series 345mm rear disc (345x 24) and the 370mm kit uses a F01 7 Series 370mm rear disc (370x24).

E60 5 Series part numbers are BMW (34116766871) BMW (34116779467) BMW (6766871)

F01 7 Series part number are BMW (34 21 6 775 291) BMW (6 775 291)

There are two different caliper cradle adaptor kits to cope with both the change in diameter and the offsets of the two disc types, 345mm and 370mm.

The kits are made of 15mm 355J2 steel with 12mm 10.9 bolts and nuts and use high tech Norlock lock washers. Tolerances on machining are 0.1mm as opposed to 1mm on most adaptor brackets.

Unlike most adapter brackets the PB rear BBK design does not use washers or spacers but is handed and machined to obviate the need for spacers / washers as these are a point of weakness in terms of torque integrity, compliance and potential loosening.