I'm at alignment school for work right now, and we were talking about how higher positive camber can increase high speed stability and make the steering a bit heavier. A lot of Mercedes and BMW cars apparently run like 9 degrees of caster for autobahn driving.
I went through some threads on here and someone recommended about 6 degrees. I don't know what stock is supposed to be, but I'm at about 5 degrees right now.
Can I increase it to 7-8? Will this noticeably increase my high speed stability or just burn up my power steering?

 

I run 7 and it's very predictable. Go to the racing section and there's an alignment thread you can post in. One guy is running 8 degrees of positive caster. My friend's E36 M3 and my buddy's E86 Z4 M coupe both run about 7.9 degrees. Some people will argue that 7 degrees is too much, but clearly they haven't driven a sports car or don't value handling. The only reason I'm seeing more people drop caster is to get more camber, but there are guys running 3-3.5 degrees of camber with 7 degrees of caster, so clearly you can have both worlds.

 

i uped mine from around 5.2 ish to 6. and def made steering heavy, but so much better all around, you can feel it turning o much more, i want to add a lil more aster like 6.5 and add some more negative camber next alignment

 

i believe people typically increase caster angles for autocross, and decrease them for HDPE

edit: by 'decrease' i mean relative to a higher caster set, not less than OEM recommended.

 

the answer is yes, try it, see what you think.

the planted feeling the german cars have is due to a few things, and lots of castor is one of them. they also typically have a polar moment that is in the front, either with a heavy engine (BMW), or putting it in front of the axle (Audi).

http://en.wikipedia.org/wiki/Moment_of_inertia
the BMW's also tend to use a slower steering rack than the typical Mazda, so it takes more movement of the steering wheel to move the tires the same amount.

a power steering Rx7 from 1986 has a 15:1 ratio, a BMW E30 has a 20:1 ratio, so the BMW is a bunch slower, which sucks when you're parking, but its good at 100mph.

i'm not sure what the Rx8 is, 17:1?

 

^^Rx8 is 16:1 I believe. My friend has an E36 M3 with an upgraded Z3 non-m steering rack that has a ratio of 14.5:1 and every time he drives my car, he says the steering feels much quicker, which I don't get exactly how that works?

 

I aligned my car today, and it was already set at 7.9 on the left and 8.0 on the right, which explains why my steering feels different than other 8s that I have driven. I am going to try to throw it up on the rack again tomorrow and set it to around 6 and see what happens.

My camber is at -1.2 on the front, and -1.0 on the back, which seems to be working great! Totally even tire wear, and excellent traction.

 

maybe he's wrong? oh actually it might be that the steering arms are different lengths or something

BMW is German for 'oh that sounds great i'll take your word for it'