Do spacers impact toe behavior?

[Asbjorn]

I temporarily swapped back to my old OEM wheels and added 12mm spacers rear just for fun. With the spacers installed, the car would suddenly turn left on acceleration and right on lift off (as you corrected by turning the steering wheel right during acceleration). After removing the rear spacers again, the problem is gone.

Is anyone able to explain this behavior?

I have tried different combinations of ET, and here are my experiences

Front	Rear	Comment
8J ET29 225/40R18 (stock)	8.5J ET40 255/35/R18 (stock)	Car drives straight, steering wheel is straight, no change of direction during braking or acceleration.
8J ET29 225/40R18 (stock)	8.5J ET28 255/35/R18 (12mm spacer)	Car drives straight, steering wheel is straight, car pulls left on acceleration
8.5J ET35 235/40R18	9.5J ET40 265/35R18	Car pulls a bit to the right, but I suspect this is caused by uneven tire wear, steering wheel is straight, no additional change of direction during braking or acceleration.
9J ET30 255/35R18 slicks	9J ET30 255/35R18 slicks	Car drives straight, steering wheel is straight, no change of direction during braking or acceleration, but the car is super sensitive to road imperfections, grips the white stripes etc. From what I have read, this is a common problem with square setups.

So somehow it seems that


ET rear < ET front: Not good
ET rear = ET front: Tolerable
ET rear > ET front: All good

I supposely run toe out at the front, toe in at the rear rear, -2.7 deg camber front and -1.7deg rear. Bearings and solid mounts almost everywhere front and rear. Only rubber left is the inner bushings for the two rear control arms.

Bonus: Here's an old table I did comparing OEM front specs across E9x and E89 .

 

[Asbjorn]

So it turned out that my problem above was due to wrong toe setting:

We ended up with these settings instead, and the problem is greatly reduced

This was with me in the car and half a tank of gas. Camber maxed out both front and rear on both sides.