The most popular upgrade for cars and trucks is new custom wheels and tires. After that, suspension upgrades are very common on both late model and older vehicles. Typically, drivers will want to simply raise or lower their car or truck for aesthetic reasons, but there are often performance reasons for suspension upgrades, as well.
Raising, often referred to as lifting, is most common on trucks and jeeps. In addition to creating a taller ride height, this is regularly done for performance reasons such as allowing for larger wheels and tires than what the factory (O.E.) suspension will allow.
There are two primary ways for lowering a vehicle: lowering springs or an adjustable coil-over suspension kit. Both of these options will give the car a lower center of gravity and stiffen the car's chassis, which will allow for less body roll in corners and improved handling and cornering. Coil-overs give the added advantage of ride-height adjustability and with certain models, dampening adjustability for fine tuning the balance of ride quality and handling.
Whether you're looking for performance shocks, gas shocks or other products to upgrade your suspension, it's important to consult with an expert. Changing a car's suspension will require alignment adjustments and may create fitment challenges with your custom rims (wheels) and tires.