Alignment settings

[4agdtym]

I'd like to have my boxster realigned to settings that are more suited to autocross and spirited driving. I believe the factory settings have too much understeer for this type of driving. Anyone worked this out? What settings should I suggest to the alignment shop?

Thanks.

[ericinboca]

I'd like to have my boxster realigned to settings that are more suited to autocross and spirited driving. I believe the factory settings have too much understeer for this type of driving. Anyone worked this out? What settings should I suggest to the alignment shop?

Thanks.

Not apples to apples as my 986S has 18" wheels and it is track dedicated (not autocross and no street use), but...

With R compound tires, I have -2 in the front with slight toe-out; -2.6 in rear with slight toe-in.

If I were making an educated guess as to what to do to an understeering autocross/street car, I definitely would give it toe-out in the front. It will probably make it meander slightly when going straight, but it is easily controlled in mine, and toe-out has been the biggest help to understeer short of adjustable coilovers, adjustable sway bars and a wider tire (which I do use to adapt the car for different tracks and conditions).

For front camber, you have to decide how much you are willing to live with the tire wear consequences. I would think you probably need -1.5 in the front, but that seems like a lot for a car that is used mostly on the street.... (a little more caster angle in the front would be good too, but the 986 does not have caster adjustability without making some changes to aftermarket parts)

You likely have toe-in in the rear now, which helps keep the rear where it is supposed to be - behind you. If you still have issues after giving the front toe-out, you can give the rear 0 toe to free it up some.

So, I guess I am recommending toe-out in front; as much camber negative camber as you are willing to give it in deference to the need to drive it on the street; go -2 in the rear with slight toe-in. See what that does for you and adjust from there....decent starting point; better than factory settings.

[grover]

Are you racing on street tires or R-comps? Do you have M030 suspension? The best alignment is going to be different for different setups.

I had terrible understeer on my 04 Boxster S (non-M030) when I first started autocrossing it. Sticking with street tires, I found going with slightly wider front tires (225/45-17) were a HUGE improvement in making the car handle more neutrally, and dialing in as much negative camber was not so muchttp://www.renntech.org/forums/index.php?showtopic=30707&st=0&gopid=166179h because there's SCCA AS restricts us to factory adjustable settings (about -.75 max) which does not allow for camber plates or anything. I left rear camber alone at -1.3 (OEM).

Beware, though, going outside of factory spec can cause uneven tire wear. Also, if all you're doing is going to the stops with negative camber, there's no fancy tools involved, just loosen the bolts and push it to the stops. If you mark the original position, you can move it back to the old position after the autocross. This has some small impact to toe, too; gives a little more toe out, which is desirable.

Changing tire pressure can help, too. Remember- the stock pressures, tire sizes and camber are all carefully selected to keep trophy wives out of ditches- NOT for best performance. For reference, after much trial & error, I ran this season on Dunlop Direzza Z1 Star Specs at 225/45-17 front @ 36psi hot and 255/40-17 rear @ 36psi hot. As you're running a different car with different tires and a different air guage (+/- 15psi with the 6 I've got laying around), you'll still need trial & error to find the right pressure for your tires.

Edited January 23, 2010 by grover