BMW M2 F87 M3 F80 M4 F82 Steering Gearbox ML 8099561

Part Number: 8099561 (Replaced by/Interchangeable with 8090461, 6886475) Manufacturer: Bosch Automotive Steering

The 8099561 is the high-precision Electric Power Steering (EPS) rack specifically tuned for the F-chassis M-Division vehicles (M2, M3, and M4). Unlike the standard 3 Series racks, the M-variant features a more rigid mounting system, a faster steering ratio, and specialized internal valving to handle the increased lateral loads of track driving and wider front tires.

Technical Specifications

• Compatibility: * BMW M3 (F80): 2014–2018

  • BMW M4 (F82/F83): 2014–2020

  • BMW M2 (F87): All models (OG, Competition, CS)

• Motor Position: Paraxial (Motor mounted parallel to the rack).

• Communication: FlexRay bus system (High-speed data transfer for real-time feedback).

• Ratio: Variable M-specific ratio for high-speed stability and low-speed agility.

Key Performance Features

• M-Specific Servotronic Tuning: The internal software allows for distinct steering “weights” (Comfort, Sport, Sport+). In Sport+, the assistance is minimized to provide maximum mechanical feedback through the steering wheel.

• Rigid Steering Column Connection: To eliminate the “rubbery” feel often associated with EPS, the M-rack utilizes higher-durometer bushings and a direct-mount bolt pattern to the front subframe.

• Active Return: The rack uses its electric motor to help center the wheels after a turn, calibrated specifically to match the aggressive caster angles of the M-chassis.

• Torque Sensors: High-resolution sensors detect driver input and road kickback, allowing the system to filter out unwanted vibrations (like tire balance issues) while retaining essential road feel.

Technical Installation & Cataloging Notes

As a safety-critical electronic component, the following steps are mandatory for installation:

1. FlexRay Initialization: This rack is a “node” on the vehicle’s high-speed FlexRay network. After installation, the rack must be “learned” to the vehicle using BMW ISTA. This synchronizes the rack with the DSC (Dynamic Stability Control) and ICM (Integrated Chassis Management) modules.

2. Coding (VO Coding): Because steering maps differ between a standard M4 and an M4 GTS or M2 CS, the rack must be coded with the correct “EPS Variant” to ensure the steering weight matches the vehicle’s specific suspension geometry.

3. End-Stop Learning: The software must be calibrated to recognize the physical limits of the rack (left-to-right lock). Failure to do this will result in a “Steering Support Restricted” warning on the iDrive.

4. Hardware Replacement: The ASA (Aluminum Stretch Bolts) used to mount the rack to the subframe are one-time use only. They must be replaced and torqued to 56 Nm + 90° to prevent the rack from shifting under load.

Warning: If sourcing a used unit, inspect the rubber gaiters (boots) for any tears. Moisture ingress into the internal ball-screw