Suspension: Strut Assembly
A strut is a shock absorber and a coil spring combined. This system was design by Earle S. MacPherson in 1947 and is now the most commonly used independent suspension found on vehicles today.
A strut like a shock absorber prevents the coil from oscillating after it hits a bump in the road. It prevents this unwanted spring motion by forcing hydraulic fluid through tiny holes in a piston located inside its chamber. This restricted fluid prevents sudden movement and helps isolate the chassis and passenger compartment from the irregular road surface. It provides resistance on both its compression cycle and its extension cycle. Without this dampening effect, the vehicle would feel like its floating down the road. A worn strut tower will make the most noise (a thunking sound) when going over bumps in the road.
Typically when replacing struts, the coil spring is reused and the shock absorber/spring seat portion is replaced. A special tool is required to compress the spring. Most shops and dealerships will have one mounted on the wall. An inexpensive pair of strut spring compressors can be used as well. Be careful, safety first. Compressed coil springs contain a considerable amount of energy. When removing the strut from the vehicle, be careful to check for any camber adjustments that can be made. If an eccentric camber bolt is found, mark its position before removal. Adjust both camber and toe when replacing this type of strut.