dyi front camber mod

[insite]

modern porsches are designed with a LOT of caster in order to maximize the effect at smaller steering angles. as a rule of thumb w/ our cars, every degree of steering angle adds almost a tenth of a degree of camber.

keep in mind, though, that this is not the only mechanism through which the suspension geometry adds camber. the car is ALSO designed to gain camber as the suspension compresses. the rates at which this occurs have to do with the inward angle of the struts & the length of the lower control arms. i don't have camber curves plotted for this car, but i CAN say that suspension compression of 1" will result in approximately -.7 degrees of camber gain. therefore, other suspension changes will modify the camber gain w/ certain amounts of weight transfer. example: soft suspension will compress a LOT, & gain significant dynamic camber through kinematic changes to suspension geometry. stiff suspension will move less & gain LESS dynamic camber, therefore more static camber should be dialed in (comparatively) to compensate.

when someone tells you that their camber is set to -1 or some such number, that is the STATIC camber. the measurement, though, is truly a dynamic parameter.

if you hit the track, you'll want to set camber based on pyrometer readings & treadwear, amongst other things. if you auto-x, the tires never really heat up & your tools will be chalk marks and tire wear.

[baxster]

I'm surprised there weren't more responses about the actual modification. I'll let you know how much camber I was able to get with the mod.

Thanks again insite and harryrcb!!

[Klimo]

This is a great read. Thanks insite. I am in the process of getting my car ready for track days, no auto x. I do about 6 track days in the summer. I am not worried about giving up some street driveablitly or having to go through tires every 10k. I use Michelin PS2s. It sounds like -.8 in the front might be enough to get what we want out of the car, but if it isn't what are my option for increasing camber on the stock suspension. I don't want to be drilling holes or anything into my suspension like what's being talked about on here. Do I need new struts? Can i jsut add camber plates? Thanks.

[insite]

Klimo -

what size are your tires? depending on stagger, you have some options.

if you need more static camber, the best place to start IMO is to lower the car. this automatically adds camber at all four corners. after that, the best options are either camber plates or GT3 style control arms.

[hcj986s]

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.