Suspension and Steering
A suspension system comes in two different designs—independent and solid (live) axle. Most cars use an independent suspension system, where each wheel moves up or down independently without affecting the other wheels. Some cars and most trucks use a solid axle suspension in the rear, where the axle moves up and down like a seesaw and the movement of one wheel causes a corresponding movement in the other wheel.
Vehicles with independent suspension systems offer a more comfortable ride and have better handling characteristics. Solid axle systems are stronger, less expensive to build, and have more load bearing capacity, but offer a rougher ride.
The two most common types of steering systems are rack & pinion (used on most cars) and recirculating ball (used on trucks and utility vehicles). The rack & pinion system is similar to the independent suspension system in that it offers better control and handling. The recirculating ball system, like the solid axle system, is stronger and more robust, which is better suited for larger vehicles and trucks.
Those of us who have driven older cars remember how hard it was to steer before power steering came along. Power steering systems use hydraulic or electric power to exert extra force on the steering gear, which makes steering almost effortless for the driver.