Alignment and PSM

[Q-Ship986]

In a 996 thread here, Loren refers to a requirement for recalibration of a steering angle sensor when the alignment is changed on vehicles equipped with PSM. However, I could find nothing regarding this in my '03 986S owner's manual. I figured that the manual would mention it since it is conceivable that an owner would have a non-dealer service the tires/wheels/alignment.

In any case, does anyone have experience with this issue?

Many thanks,

--Brian

[adsach]

In a 996 thread here, Loren refers to a requirement for recalibration of a steering angle sensor when the alignment is changed on vehicles equipped with PSM.  However, I could find nothing regarding this in my '03 986S owner's manual.  I figured that the manual would mention it since it is conceivable that an owner would have a non-dealer service the tires/wheels/alignment.

In any case, does anyone have experience with this issue?

Many thanks,

--Brian

<{POST_SNAPBACK}>

I have had 3 or 4 alignments on my '02 985S. The camber changes in the rear have ranged from -0.3 to -1.2, front from 0.2 to -0.5 with minimal adjustments to toe. At no time has the dealer or independent mechanic mentioned anything about calibrating the steering angle sensor for PSM.

I forget the slip angle limit (derived from the yaw & steering angle sensors) that invokes PSM intervention. It is reasonable to assume that helpful slip angles in the 5-7 degree range could be miscalculated significantly by a few degrees of misalignment in the steering angle sensor.

IMO-Your concern seems well founded, but I have not experienced a change in center line of the wheel after an alignment, or an obvious change in PSM intervention.

[magcuda]

with PSM when doing alignments you are supposed to recalibrate the steering wheel sensor-with the factory tool- but the guys at the dealer set the steering wheel sensor to zero and align the car from there. The Baum Tool works that way, set the steering wheel sensor to zero, lock down the steering wheel, then align the car. this puts the car square. but this is for cars with PSM only

[Loren]

The steering angle sensor (PSM cars only) is supposed to checked at each alignment - but rarely needs changing.

Just so folks know... the Baum Tools Porsche Scan tool (with Porsche software module) is $3700. It looks very good but I could buy a used PST2 for that and have a lot more capability.

[Q-Ship986]

It would seem to me that the alignment issue for the steering angle sensor is for changes to front toe only--assuming, as I am, that this sensor is monitoring something in the steering system, i.e. the steering column. Continuing with that assumption, if the steering wheel is level from the factory, remains level through vehicle use, and the total toe is split evenly from side-to-side, the sensor would not change it's relative fix on zero, presuming the sensor doesn't drift, or isn't otherwise faulty. Therefore, if changes to front toe are done properly with the steering wheel fixed level and total toe split equally to both sides, I can't see any real affect on this sensor. Which is, apparently, the practical experience reflected so far. But I am wondering, do the assumptions and theory make sense? Again, this wasn't mentioned in my owner's manual; maybe it is in a maintenance guide, which I didn't check....

--Brian

Edited August 12, 2005 by Q-Ship986

[adsach]

--assuming ... the total toe is split evenly from side-to-side ...  But I am wondering, do the assumptions and theory make sense?  --Brian

<{POST_SNAPBACK}>

I don't have the numbers, but after a year of driving, my factory set toe was negative on one side and positive on the other, my front camber numbers were also off 0.4 side to side (uggh).

After a precision alignment I experienced handling that was 'better than new'.

IMO - it isn't safe to assume a good alignment as factory delivered.