It's fairly common for car owners to modify their cars' suspensions to make their car ride lower. Usually, aesthetics is one of the main reasons for lowering the ride height – many people prefer the look of a lower car – but in theory, there are other benefits:
- Handling can be improved by lowering the vehicle's center of gravity, which reduces the tilt of the car.
- Lowering the vehicle usually reduces aerodynamic drag, which increases fuel economy and sometimes reduces high-speed lift, which makes the vehicle safer. (These effects are usually quite small for realistic amounts of reduction).)
- A lower vehicle can present a lower rollover risk. (Most cars are extremely difficult to roll under normal conditions, so this is a minor consideration at best).
Some aftermarket suspensions improve handling in ways other than lowering the car, so lowering can only be considered an added benefit. This is the theory. But what about in practice: is lowering a car a good idea, and is it safe?
It turns out that the answer depends primarily on exactly how you plan to lower the car.
How to lower a car
On the one hand, expensive (several thousand dollars) aftermarket kits (often with coilovers) carefully designed for each car model for which they are offered. Many of them lower the vehicle (although that's not necessarily the main purpose) and well-designed kits that have been properly installed are safe.
On the other hand, there are a variety of approaches in which only a few or none of the existing parts are replaced. Instead, existing parts, typically springs or torsion bars, are modified.
Common changes include:
- Shortening or softening springs
- Re-bending leaf springs
- Changing the spring or torsion bar mounting points
- Adjust torsion bar wrench (torsion bar suspensions only)
Unfortunately, these low-cost approaches can be harmful to your vehicle or even make it unsafe to drive.
How lowering a vehicle can cause damage
The first concern is the lowering process itself. Most automotive repairs and modifications should be done by a professional, but this is even more true for suspension work than almost any other type. Automotive springs exert thousands of pounds of force, and if you don't follow proper procedures when removing and reinstalling them, they can cause serious injury or death. Always leave suspension work to your qualified mechanic.
But if you've done the job properly, what are the dangers of lowering your car or truck? The most common are:
- The lowering process can change the camber (at rest or when the wheel is raised as if over a bump), which in turn has two negative effects, reduced traction, especially under braking, and increased tire wear.
- The steering geometry can be changed so that the vehicle cannot be steered safely. This applies primarily to cars that have been lowered several inches or more.
- A vehicle that has been severely lowered may go down at driveway entrances or fail to clear normal road obstacles. Also, if you need your car towed, you may find that it cannot be towed normally (a flat bed may be required) or that there is no way to damage the car.
- Shock absorbers can experience more force (along their length or sideways) and reduce their service life.
- A lowered vehicle can put extra stress on other parts of the suspension and steering system, leading to excessive wear and even premature failure.
- Tires can rub against sheet metal or hanger components and damage both.
- The ride will almost always be harder because most lowering procedures reduce suspension travel. This can be uncomfortable for you and your passengers, and can also increase wear and tear if your car gets hit harder.
Most of these problems do not result in a serious threat to life or limb. The exception to this rule is extreme camber changes, which can reduce braking performance enough to make the car unsafe; it can cost a "camber kit" available to prevent this effect, but it is important not to drive a vehicle whose camber deviates greatly from stock. Similarly, it is important to ensure that the steering system functions properly after it has been lowered. This is usually not a big risk if a car is only lowered an inch or two, but beyond that, it may be necessary to make significant changes to make sure the car is safe.
Many of the other disadvantages can be reduced or eliminated by appropriate measures; For example, achieving wheel alignment after any suspension work, including lowering, can eliminate the increased tire wear problem. And if a tire rubs the sheet metal, it may be possible to roll the edge of the fender or quarter panel enough to eliminate the problem.
It's important to understand that while the serious mechanical problems may be preventable, almost any method of lowering your car will result in a harsher and, for many people, less comfortable ride, and most owners of lowered cars will experience increased wear and tear on various components.