It’s a pretty common train of thought that lowering a car lowers the center of gravity and improves handling. Unfortunately that is not the whole story. When it comes to handling performance, keeping the tire in optimum contact with the road is the most important consideration. That means that the tread is flat on the ground, and has the most consistent contact with the ground possible. So with that said, lets go over a few things that happen with the car is too low.
The first problem that occurs with a lowered car is a reduction in bump travel. If you don’t have enough bump travel, you’ll be hitting the bump stops or even riding on them all the time. That takes away from the struts and springs being able to do their job, and creates sudden loading increases to the tire. Remember what I said about keeping consistent contact with the ground? Well hitting the bump stops is not consistent contact. This sudden bump in load drastically reduces grip. If your car is too low, you may feel this as a skipping or unsteady feeling while cornering over bumps, or perhaps just a general lack of grip. It will certainly make your laptimes significantly slower.
But wait, there’s more!
There’s something called a roll center. The roll center is a point the body of the car tries to roll about. Or, more specifically, the point the center of gravity tries to roll about. So if you increase the distance between the roll center and center of gravity, you increase the roll couple, and therefore increase body roll given the same lateral force. So that’s fun, right? Generally speaking, lowering a car lowers the roll center. All else the same, this INCREASES body roll. With this little tidbit, we’ll move onto what’s called the camber curve.
Remember that part I said about keeping the tread flat on the ground? That’s where the alignment and camber curve come in. As the suspension moves through it’s travel, the alignment changes. Ideally, negative camber will increase with bump and toe will experience little to no change. With double wishbones and multi-link suspension, this is pretty common. Camber gain is important because in a corner the car leans over and the outer tire leans over. Using the suspension geometry to lean the tire inward with bump keeps the contact patch flat with the ground and increases grip. Most suspension geometry does not do this well enough, especially when the car has been lowered. Most macpherson strut systems (used on subarus and evos for example), will lean the tire in a bit at first, and then lean the tire outward. That means the tire is riding on the ouside edge and sidwall. Guess what that does for grip?
So, in conclusion, lowering your car too much will cause you to ride the bump stops, increase body roll, and reduce the amount of tread in contact with the road. Any of those three are cause for concern when lowering a car. Most of the time, when a car is lowered, all three come into play. And that’s just not functional.