Steering
SteeringThe MINI features a power assisted steering system (EHPS) on all models. EHPS is a system not previously seen on BMW vehicles. The steering rack is of conventional rack and pinion design. The steering column has two collapsible mechanisms and tilt adjustment. The twin spoke steering wheel is common to all models although there are small differences depending on the model and equipment level. The steering column has 54 mm of tilt adjustment manually controlled by a lever beneath the column. The electrically driven power steering pump is the main difference.
Purpose of the System
The Steering System is designed to offer smooth operation with maximum feedback to the driver. The Electro Hydraulic Power Steering, driven by an electric motor rather than the conventional belt, conserves valuable engine power and provides a 3% savings in fuel economy.
The main components of the steering system are:
- Electro Hydraulic Power Steering Pump (EHPS)
- Rack and Pinion
- Steering Column
- Steering Wheel
System Components
EHPS
All models and derivatives are equipped with Electro Hydraulic Power Steering (EHPS). This system uses an electric motor to drive the hydraulic pump. This replaces the customary design whereby the pump is permanently driven from the engine via the auxiliary belt. The EHPS motor weighing 5.5 kg is mounted by four rubber insulators and is positioned in front of the steering rack.
The hydraulic pump displaces 1.25 cubic cm / revolution developing a pressure of 105 bars at a maximum pump motor speed of 4,200 rpm. The hydraulic pump has an incorporated pressure relief valve. The smaller metal pipe from the aluminum bodied pump is the high pressure side and the flexible pipe fitted to the plastic reservoir on the pump is the low pressure side. There is a small reservoir fitted to the end of the pump with a remote reservoir fitted to the bulkhead. The system is filled with Pentosin CHF 11 S. For top-up and refill use the same oil.
Rack and Pinion
The Steering Rack is mounted on the front subframe and is of conventional power assisted rack design. The rack is 2.56 turns lock to lock.
Steering Column
The steering column is mounted on a one-piece aluminum bracket attached to the cross car beam. The steering column features two collapsible mechanisms, the upper part sliding away from the driver and the lower part telescoping to allow for movement of the engine and sub-frame during an impact. Vehicles equipped with DSC have a steering angle sensor fitted to the lower end of the upper column. The data is transmitted to the DSC control unit via the CAN bus. A grommet with an integral bearing seals the column to the bulkhead and provides additional support at the bottom of the column. A "Yoke" type joint secured by a nut and bolt secures the column to steering rack pinion. The ignition switch, steering lock cylinder and gearbox interlock (ECVT cars only) is mounted on the steering column tube. The interlock prevents the ignition key from being removed until the ECVT lever is in the Park position. A slip clutch is fitted beside the steering lock detent pin. If force is exerted on the steering wheel, this prevents the detent pin from shearing off. This improves anti-theft protection. To reduce weight the column/lock assembly is made from pressure die cast magnesium. The rotary coupler for the airbag is attached to the steering column switch unit. This is screwed to the top of the column. The steering column has a tilt mechanism that allows the steering wheel to move 27 mm up and down from the center. Thus providing a total tilt adjustment of 54 mm. Adjustment is made by means of a lever located under the column cover. The column is counterbalanced by two springs, one either side of the column.
Steering Wheel
All models feature a two-spoke steering wheel. The MINI COPPER rim is vinyl. The MINI COOPER S (and optional MINI COOPER) steering wheel is leather trimmed. The diameter of the steering wheel is 370 mm. The steering wheel airbag module has a capacity of 57 liters and is a two-stage bag. There are a number of functions that can be performed without the driver having to remove his/her hands from the steering wheel. Situated on the outside of the two spokes are the horn push buttons, these are on all steering wheels on all derivatives.
- Cruise control buttons (if equipped) are laid out on the wheel in the following manner. Cruise on & resume buttons are on the left hand side and speed increase and decrease plus SET on the right hand side, these are located underneath the horn buttons.
- Audio system remote controls (if equipped) are located on the back of the steering wheel. On the left hand side is station search + and - these buttons only search the station presets. On the right is volume + and - and in the middle is a mode button to change to bass, treble, balance and fade. These are rocker type switches.