I recently had some Cusco Zero-2 Coilovers and a Relentless Autosports Front Strut Tower Bar installed and I noticed a significant change in handling... for the worse. My front outside tire starts slipping around 40/45 mph on freeway on/off ramps now and I used to take a turn daily at 50mph with no slipping but now my tires start slipping at 45 mph. Below is my suspension set up:

Before -
Cusco F + R Sway Bars (front set at stiffest)
GT Spec F + R Lower Tie Bars
GT Spec Rear Lateral Arm Bar

After -
Cusco F + R Sway Bars (front set at stiffest)
GT Spec F + R Lower Tie Bars
GT Spec Rear Lateral Arm Bar
Cusco Zero 2 Coils (all shocks set at 3 stiffness out of 5, Front is lowered half an inch, Rear is lowered 3/4 inch)
Relentless (VRT) Front Strut Bar

What can be causing this and how can I improve the handling?

Here are the only things I can think of but I am not sure which if any would help.

1 - adjust the stiffness of the front shocks (not sure if they should be stiffer or softer)
2 - remove front strut bar
3 - set front swaybar to the less stiff setting
4 - change the height of the coilovers

Would some of you who are knowledgeable about suspension tuning chime in with some ideas or recommendations? Any comments welcome, I am sure I didnt think of all possible solutions.

 

when you installed the coils, did you get the car corner balanced?? Also did you get front and rear camber arms??

 

No and No, I just got an alignment. Everything from the alignment was in within the stock specs except the cross caster (-0.9) and camber (-1.3 on the fronts and -2.4 on the rears). but these values were close to what I had on stock shocks/springs

 

You went from OEM front 314 lbs springs to 560 lbs Cusco springs and now have understeer? Sure:
“In general, you could say that stiffer springs yield less grip on that end of the car”
“The car's tendency toward oversteer is generally increased by softening the front suspension or stiffening the rear suspension.”

Try:
-softer roll bar on the front
-soften front shocks
-increase front tire pressures (+2 psi?) and/or decrease rear tire pressure
-mount wider tires in front
-stiffer springs on the rear
-lower the front ride height

Also check tire temps.
What is your toe set up at?

 

corner weighting could be an issue, does it understeer the same in both directions?
camber still seems high
I think I'd probably start by softening the front anti-roll bar and see where that goes.

 

Who did the install?

As a first check, make sure that when the Cusco Sway, GT Spec bars and Front Strut bar were installed, that the cars suspension was loaded (wheels on ramps or on the ground). The point is to tighten the nuts and bolts on the suspension when the car is loaded.

(Before getting the car corner balanced), if you don't have adjustable endlinks for your front and rear sways and just got coilvers installed, chances are your Front and Rear sways are pre-loaded (unless the installer adjusted the coilovers by measuring from the center of the hub to the fender edge). This will hinder the sway bar from performing as designed.