Can dealer change steering assist levels?

[MarkC]

The dealer hooked up their computer to the Z4's electric power steering system for a diagnosis. Afterwards while driving the car I notice there is more power assist than before. To explain it's as if the car's electric steering assist is on over boost. The feel of the road from the steering wheel is almost nil.

The diagnosis was for the sticky-steering, and now I suspect they adjusted the boost as a 'fix-all' for such complaints as tramlinging or those who aren't used to higher effort steering of a sports car.

As well known, at parking lot speeds, the power steering assist is full, to make it easy to park. As speeds increase, so does the the level of assist decrease. At highway speeds, there is suppose to be very little if no power assist. With the sport button engaged, the assist level is lessened. I suspect it is speed related, meaning as the speeds increase, so does the level of assist decrease, and it's this map (speed level) that is changed when the sport button is engaged.

I made a simple graph. It is not precise, as I don't have the actual numbered data (wish I did), what's represented is 'seat-of-pants'





Anyone know if the dealer can change the power assist level, or when the assist finally decreases? Pressing the sport button helps, but even with it on, the steering still feels lighter than before with the sport button off.
thanks

[GVfB]

they have reset the "dead center" point. On the steering shaft there is a cluster with 360 sensors, each sensing a 1° steering change. If the sensors are off compared to the wheel alignment, the servomotor tries gently to return the steeringwheel to the theoretical dead center point.

Idealy, each wheel alignment must be followed by a dead center reset... but this can only be done with a BMW DisPlus computer.

The power assist is not speed sensitive and is continuous regardless of speed (if I remember correct)...

[Roadster]

The power assist is not speed sensitive and is continuous regardless of speed (if I remember correct)...

The assist is completely dynamic and speed sensative! That's the huge benefit of electric assist steering! BMW refers to this as "Servotronic".

[GVfB]

Roadster - okay, I stand corrected

[MarkC]

Here's a graph from http://www.powersteering.com.ua/servotronic_eng.html

Characteristic curves of the ZFServotronic. The diagram shows how pressure and the torque required at the steering wheel vary with the driving speed. The shape of the char- acteristic curve may be adapted to match the character of the vehicle.

The above is a generic description of Servotronics and not specifically the Z4's.