This IronBox adapter kit is designed for the rear axle of BMW E30 and BMW E36 Compact models fitted with 5×120 drum-brake trailing arms ⠀ It provides mounting positions for two brake calipers on each side — one for the main braking circuit and one for a separate hydraulic handbrake circuit ⠀ For BMW E30 models with the original 4×100 rear drum-brake configuration, the factory hubs must be replaced with BMW E36 Compact 5×120 rear hubs ⠀ The conversion uses BMW E36 rear brake discs and matching rear calipers, with either vented or non-vented components ⠀ Using a dedicated second pair of calipers keeps the hydraulic handbrake circuit separate from the main rear braking system ⠀ The adapters are manufactured from steel, finished with powder coating, and supplied as a left- and right-side pair with the required mounting hardware ⠀ Main features ⠀
Dual-caliper rear conversion — provides mounting positions for two brake calipers on each side
Independent hydraulic handbrake circuit — keeps the handbrake separate from the main braking circuit
Rear drum-to-disc conversion — replaces the original rear drum-brake configuration with BMW E36 disc-brake components
5×120 configuration — designed for BMW E30 and E36 Compact drum-brake trailing arms with 5×120 hubs
BMW E30 4×100 conversion compatibility — can be used after installing BMW E36 Compact 5×120 rear hubs
Multiple brake configurations — compatible with matching vented or non-vented BMW E36 rear discs and calipers
Complete adapter pair — supplied with the required mounting hardware
Steel construction — suitable for drift, track, and performance builds
Powder-coated finish — provides corrosion protection and a clean appearance
Designed and manufactured in Ukraine by IronBox
⠀ Compatibility ⠀ Compatible with: ⠀
BMW 3 Series E30 with a 5×120 rear drum-brake configuration
BMW 3 Series E30 with original 4×100 drum-brake trailing arms after installing BMW E36 Compact 5×120 rear hubs
BMW 3 Series E36 Compact with 5×120 rear drum-brake trailing arms
⠀ Not compatible with: ⠀
BMW E30 or E36 Compact rear trailing arms originally equipped with disc brakes
BMW E30 4×100 hubs without conversion to BMW E36 Compact 5×120 hubs
Other rear trailing-arm or braking configurations unless confirmed before ordering
⠀ Compatibility is determined by the installed rear trailing arms, hubs, brake discs, and calipers rather than only by the vehicle model or engine ⠀ Required parts — not included ⠀
BMW E36 rear brake discs — vented or non-vented
Two matching pairs of BMW E36 rear brake calipers for the selected disc type
BMW E36 Compact 5×120 rear hubs — required only for BMW E30 models retaining the original 4×100 drum-brake trailing arms
Hydraulic handbrake
Brake lines, hoses, fittings, and brake fluid
⠀ Brake discs and calipers must be used as matching compatible sets ⠀ Kit includes ⠀
Left-side dual-caliper adapter — 1 pc
Right-side dual-caliper adapter — 1 pc
Installation hardware
⠀ Important installation information ⠀ This product changes the vehicle’s rear hub and braking configuration ⠀ Installation, hub selection, caliper alignment, brake-line routing, bleeding, and final testing must be carried out by a qualified specialist ⠀ Do not operate the vehicle until the complete braking system has been properly inspected and tested ⠀ Any brake components that differ from the configurations listed above must be confirmed before ordering