Struts are one of the main components of your car's suspension system. They are comprised of two main parts: the coil and the shock absorber.
A coil is a piece of metal in the shape of a corkscrew that compresses when a force is applied to it and extends when the force is released. There are coils at the bottom of pogo sticks that make them bounce, and the ones on cars function in a similar way.
If your car didn't have any kind of suspension, driving it would be a much less comfortable experience. Roads that are perfectly flat don't exist; every road has rifts, grooves and other imperfections on its surface. When your tire passes over a bump, instead of the whole car feeling the impact, the coil for that wheel compresses to absorb it. If there were nothing to stop the car's frame from bouncing on the coil, however, it would continue to do so until finally coming to a rest and it would be nearly impossible to handle turns. This is where shock absorbers come in.
Shock absorbers are designed to stop the bouncing motion of the coils and provide the stability you need to drive your car. They resemble a bicycle pump - the kind that you operate by hand. When you push down on a bike pump to build the air pressure, you'll notice a fair amount of resistance. A shock absorber has the same effect, but it has resistance in both directions and is filled with hydraulic fluid instead. In essence, when you drive over a bump and the coils begin to compress and extend under the weight of the car, the shock absorber provides resistance so that the car's bounces just enough to minimize the effect of the bump.
Working together in the strut assembly, the coil and shock absorber make it possible for you to drive with stability. Their simplicity and effectiveness make them one of the most popular and reliable forms of suspension implemented in cars today.Struts Ottawa