Here the bottomline on lowering your car.
Many think that the keys to good handling are super-low profile tires, stiff springs, rock-hard shocks, wrist-thick "sway" bars, and slammed-to-the-ground suspensions. "Many" are mistaken. Done haphazardly, these "improvements" can make a car SLOWER around a racetrack and punishing on the street.
Radical Lowering
Let's start with radical lowering. It's easy to take the suspension out of its optimal operating range, which means the tires aren't level with the road during braking and cornering. Do we need to say that this hurts grip? Also, an over-lowered suspension will likely toe in or out as the wheels move over bumps and during cornering. This is called bump-steer. If bump-steer happens in the rear, it feels like you're driving a hook-and-ladder fire truck with an uncooperative trailer driver. In the front, it feels as if the steering has a mind of its own.
Even worse is when the over-lowered suspension hits the limit of its travel during a hard corner. The suspension literally bangs into its bump stop. The spring rate at that corner goes toward infinity and the grip goes toward zero. If this happens to the rear suspension in a hard corner, the car will snap sideways. If the front hits its bump stop, the car will take off on a tangent as if you were swinging a rock on a string and suddenly let go. Either way, it's totally unpredictable for the driver. One of the worst things for a driver is a suspension that just barely taps the bump-stops every now and then—the car acts like it's demonically possessed and the poor driver can't figure out why.
Show or Go?
Racers lower their cars to reduce the center of gravity, which can improve cornering. But then they raise suspension-mounting points and install completely redesigned components, so the suspension remains in its designed operating range. For the street, slammed suspensions are strictly for show, not go.
Total Package
If you're determined to lower your suspension, buy a complete kit from an established tuner. Talk to someone who's installed the package. Stiffening suspension springs or anti-roll bars (often incorrectly called sway bars) REDUCE grip on that end of the car. The correct technique is to use as soft a spring/bar package as will do the job.
