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hcj986s · 05-24-2011, 09:58 AM

Insite as usual has got this exactly right. The only thing I'd add is that 1 degree isn't necessarily too much for street tires (or any other tire for that matter) if your suspension is really soft. As the car rolls, the suspension compresses and the geometry changes. As the suspension compresses, camber typically decreases (more negative) (although this is not the case with typical MacPherson struts). Let's say that the stock setup adds 1 degree of negative camber for every 2 inches of compression, which occurs at 1 g.

If the stock setup has 4 degrees of roll per g, then the outside wheel might develop positive camber despite the suspension compressing (you've seen pictures of Boxsters with positive camber on the outside wheel). After all, -1 degree plus 4 degrees of positive roll gives +3 degrees of camber.

Stiffen the suspension to 2 degrees of roll per g and set the car up with 2 degrees of camber static and the story changes: at 1 g, the outside tire is now vertical to the pavement, giving an optimal contact patch. Lower the car, and the roll center falls, increasing the roll rate further.

One final note: static camber is properly set by measuring tire temperatures at the track. If the outside edge is running hotter than the inside edge, then you need more negative camber.

My 50% stiffened 944 Turbo ran 0.8 degrees of static camber in the front with a 1.8 degree per g roll rate. I have yet to get the Boxster out on track.

05-24-2011, 09:58 AM	#22
hcj986s Registered User Join Date: Dec 2010 Location: SW Connecticut Posts: 9	Camber Insite as usual has got this exactly right. The only thing I'd add is that 1 degree isn't necessarily too much for street tires (or any other tire for that matter) if your suspension is really soft. As the car rolls, the suspension compresses and the geometry changes. As the suspension compresses, camber typically decreases (more negative) (although this is not the case with typical MacPherson struts). Let's say that the stock setup adds 1 degree of negative camber for every 2 inches of compression, which occurs at 1 g. If the stock setup has 4 degrees of roll per g, then the outside wheel might develop positive camber despite the suspension compressing (you've seen pictures of Boxsters with positive camber on the outside wheel). After all, -1 degree plus 4 degrees of positive roll gives +3 degrees of camber. Stiffen the suspension to 2 degrees of roll per g and set the car up with 2 degrees of camber static and the story changes: at 1 g, the outside tire is now vertical to the pavement, giving an optimal contact patch. Lower the car, and the roll center falls, increasing the roll rate further. One final note: static camber is properly set by measuring tire temperatures at the track. If the outside edge is running hotter than the inside edge, then you need more negative camber. My 50% stiffened 944 Turbo ran 0.8 degrees of static camber in the front with a 1.8 degree per g roll rate. I have yet to get the Boxster out on track.