Rear Axle Steering, Basic Function - GF46.80-P-9900A
Model all (CAR) with code 201 (Rear axle steering)
Model all (CAR) with code 216 (Rear axle steering with large angle)
Model all (CAR) with code 501 (360° camera)
Example illustration of steer direction of rear axle steering
Overview
This document contains information on:
- General
- Function
General
Rear axle steering is automatic steering on the rear axle. It is used to improve driving stability and comfort in various speed situations. It also improves the turning circle when parking the vehicle.
Rear axle steering is always active and cannot be deactivated by the driver.
Control is adopted by integrated vehicle dynamics control Integrated vehicle dynamics control is implemented in the ESP control unit® and in the rear axle steering control unit and initiates targeted individual wheel brake interventions as well as rear axle steering Optimization is achieved with regard to vehicle dynamics and driving stability.
Depending on the driving situation the rear wheels are steered either in the opposite direction of (A) or in the same direction as (B) the steer direction of the front wheels.
Function
Steering in the opposite direction
When steering (A) in the opposite direction the wheels on the rear axle are steered in the opposite direction to the front wheels If the strategy of steering in the opposite direction is used the vehicle's turning circle decreases and the vehicle responds in a more agile and nimble manner due to the yaw increase There are significant advantages when it comes to parking the vehicle with a large steering angle.
Steering in the same direction
When steering in the same direction (B) the wheels on the rear axle are steered in the same direction as the front wheels Steering in the same direction is applied at speeds higher than 60 km/h There is increased driving stability because of the resulting yaw damping The driver and other vehicle occupants will perceive driving maneuvers such as lane changes as being significantly more comfortable.
Steering strategies
Up to four different steering strategies with different maximum rear wheel steering angles are used depending on the model series The steering strategies cannot be selected but are determined based on the driving situation.
- Parking (up to 10°)
- City agility (up to 4 5°)
- Vehicle dynamics increase (up to 2 5°)
- High-speed stabilization (up to 2 5°)
The Parking function reduces the turning circle and increases the vehicle's maneuverability by steering in the opposite direction.
The City agility function increases the maneuverability of the vehicle by steering in the opposite direction in urban traffic.
Vehicle dynamics increase boosts the vehicle's maneuverability through the following functions:
- Steering in the opposite direction, particularly in fast tight curves →Increase of yaw angle
- Steering in the same direction particularly for extreme load changes (e g in s-shaped curves) → Wheelbase extension
The high-speed stabilization function increases the vehicle's driving stability at high speeds by steering in the same direction in evasive maneuvers and lane changes.
Snow chain mode
It is possible to use snow chains with steered rear axle for snow and ice If snow chains are used the driver must activate snow chain mode via the head unit.
The maximum steering movement is restricted to prevent the snow chains colliding with the wheel arches.
| Function schematics | |||
|---|---|---|---|
| Function schematic for rear axle steering | Model 206, 223, 297 with code 201 (Rear axle steering) Model 223, 297 with code 216 (Rear axle steering with large angle) with code 501 (360° camera) | PE46.80-P-2500-97A | |
| Detailed information | |||
| Rear axle steering, detailed information | Model 290 as of model year 2021 with code 201 (Rear axle steering) Model 206, 223, 297 with code 201 (Rear axle steering) | GF46.80-P-0020A | |
| Model 223, 297 with code 216 (Rear axle steering with large angle) with code 501 (360° camera) | GF46.80-P-0020B | ||
| Control units | |||
| Electronic Stability Program control unit, basic function | GF42.45-P-9890A | ||
| Rear axle steering control unit, basic function | Model all (CAR) as of model year 2021 with code 201 (Rear axle steering) Model all (CAR) with code 216 (Rear axle steering with large angle) | GF46.80-P-9890A |