JohnBoyToo

While the manual is the correct place to START,
it's not the final word -
especially if they are no longer stock tires and /or wheels as for the OP....

While not having an S4, I've always gone by the chalk test for my varied vehicles: http://www.ehow.com/how_6948382_chalk-tires.html

as it takes into account YOUR tires, YOUR load, YOUR vehicle...

but then again, it's not THAT critical as long as it's close

Tweakophyte

I thought it was the other way around... lower pressure means more grip, higher means less. Less grip on the rear would allow for the oversteer.

I say this because when you are stuck in the snow, you can get better grip by letting a few pounds of air out of your tire. (By the way, all of this is small changes.)

4CE FED NOGARO

I usually run 45 in the front and 42 in the rear. I have never had any problems. Max PSI is 50. I have the 255/35 R19 Titaniums.

L0U

i like high pressure to. 40ish.

phil47

That is the case for loose surfaces. For dry pavement it's generally the opposite (although you can also go too high a pressure and eventually reduce grip).

Most engineers design vehicles for neutral balance to slight understeer as it's safer than oversteer.

uberwgn

Correct. Thank you.