Alignment help needed with modified suspension!

[zmon1300]

Hi all,

I have revamped the suspension on my 04 boxster for track duty and light summer backroad driving.


Here is what I installed on the car.

ECS Tuning Coilovers (camber plates on the top, adjustable dampening from top)
New front control arms with Powerflex purple bushings with maximum caster sleeves
SPL Adjustable Sway bar end links Front and Rear
Eibach Front sway bar (non adjustable) 26mm
Eibach Rear sway bar (3-way adjustable, tubular) 22mm

Attached are some screenshots of the parts.


Looking for the best alignment specs for this car to make it handle like a gt3 or rs.
Hoping to do more track driving this year but also driving this in the summer as well.
Not looking for jaw wrenching stiffness if that helps!



I have not found many posts with good alignment specs thats agreed upon. All I know is to max out the negative camber on the front, subtract one degree from front camber for the rear camber, and zero out the toe.

Is that truly the best setup? Looking for feedback. What about Caster?

[The Radium King]

caster only has any effect on the front - it impacts turn-in (think shopping cart wheels) so playing with caster on the back doesn't do anything. note that playing with caster on the front will move the wheel in the wheel well such that it might look a bit funny and could cause clearance issues (esp when turning) if you are running max rubber.

i don't have a value for you as i kept mine stock, but check on rennlist as the 996 guys (esp gt3 folks) do play with it. here's a thread w some info ...

https://rennlist.com/forums/996-forum/1143460-suspension-adjustment-to-correct-caster-3.html

[thstone]

"max out the negative camber on the front, subtract one degree from front camber for the rear camber, and zero out the toe."

Yes, this is a great place to start and about as good of an alignment that you're going to get from a Boxster with staggered tire setup. Unfortunately, this will not get you anywhere near GT3 or RS handling.

The next step is to add adjustable lower front control arms (the 996 GT3 front lower control arms) and go to a "square" setup with another set of rear wheels and tires in the front. This will let you get at least -3 deg camber in the front which gives the front a ton more grip and eliminates understeer. When you go square, you will also want to install the front and rear adjustable sway bars. If you just install the wider tires in the front, you'll get a lot of oversteer in the rear. The adjustable sway bars allow you to fine tune the handling to mostly neutral. With a set of grippy summer performance tires, the car will handle more like the GT3/RS feel that you're looking for.

And you really don't want jaw wrenching stiffness if your goal is to go fast. You need balanced control that inspires confidence to push the car to its limit. Thus, most Spec Boxsters have the adjustable rear sway bar on the least stiff setting or even disconnected to allow the rear suspension to do its job keeping the rear tires firmly and squarely on the pavement. The front adj sway bar would be set at the middle setting to start and then adjust to your preference from there.

Best of luck.

[zmon1300]

Hey everyone,

Ive installed these parts and took it to the alignment shop. Here is what they were able to get out of all the adjustable suspension bits.

Fronts =
-2.6 and -2.3 degrees of camber
9.7 and 8.9 degrees of caster
.06 toe

Rear =
-3 and -2.9 camber
.13 and .09 toe = .23 toe


Initial drive: The turn in is awesome on it! I have the rear sway bar set in the middle and I am noticing the rear is unstable at speeds over 100mph in a straight line. Very scary to say the least. Ive also had the spring preload adjusted and the car raised to its highest point on the ECSTuning coilovers which is still a 1.5 inch drop in the front and 2 inch drop in the rear. Not very happy with the coilovers. Its spine breaking whenever I go over bumps - even with the dampening set to full soft. Spoke to the shop and they are willing to swap them out for BC Racing for the difference in cost.

The BC Racing spring rates are 3.5k/6k while the ECS coilovers are 6k/12k -- I believe this will make the ride MUCH smoother.

Do you believe I will suffer in the rear camber dept since the BC Racing do not have rear camber plates? Or should I get the adjustable arm in the rear to help fix toe and hope the rears fall into place?

[The Radium King]

2" at the rear seems like a lot of lower and i would suspect rear bump steer is contributing to your instability. (when you get low like that the rear toe control arm - or tie rods if talking the front of the car - are at a funny angle relative to the wheel carrier and bumps in the road cause changes in the toe which make the car dart around - toe control arms/tie rods with spacers allow you to get them level in a lowered car so that the geometry is correct and the dynamic alignment doesn't go wonky).

further, when you get that low the LCAs (coffin arms) go past horizontal and when you compress your suspension (ie in a turn) your camber actually decreases.

i think your thoughts are correct; better coilovers with less lower, and if necessary some adjustable rear toe control arms that also allow you to adjust for bump steer. honestly, i'm amazed that they were able to get your rear toe in spec with oem toe control arms and a 2" lower. in the interim perhaps soften your rear bar as much as possible to allow the rear to roll into all that camber you have.