What is a Shock Absorber and what does it do?

A shock absorber is an integral part of the suspension system. Its job is to slow down the up and down movement of a car suspension caused by hitting a bump. To do this the top is usually attached to the vehicle frame and the other end is attached to the lower control arm or axle. This allows the springs to provide give in the suspension and the shock to slow the movement of the spring. When the shock slows the spring down it allows the tire to keep in contact with the road instead of skipping along the road.

How does a shock absorber work?

All shock absorbers are designed and work the same way. They are sealed tubes filled with fluid that have a piston attached to a rod that moves up and down inside the tube. There are 2 common types of shocks; Mono Tube and Twin Tube. Each one operates a little differently. Let's take a look at how they work.

What is a Mono Tube Shock?

A Mono tube shock means it only has one tube for the fluid to move inside of. These shocks usually work by having the fluid move past the piston. In this type of shock the Piston is called A Combined compression-rebound valve. The valve is built into the piston and as it moves up and down the valve allows fluid to move past it. This restricts the movement of the piston which allows it to control the suspension. Sometimes these shocks will have a second chamber built into them that contains high pressure gas. There is another piston that separates the gas and oil chambers. This allows room for the oil to expand without it leaking out of the shock.

What is a Twin Tube Shock?

A twin tube shock is a type where the tube that holds the oil is inside of another tube. This design has a solid piston that pushes fluid through a valve at the bottom of the inner tube and allows fluid to flow to the outer tube. This outer tube is where the expansion area for the fluid when it gets hot. With this design the fluid is pressurized in the outer tube. This type of shock is built for comfort because of the ease that the fluid flows. It does have a drawback. A twin tube design is more susceptible to the fluid foaming if constantly going over rough roads.  When the fluid foams the shock starts to lose its effectiveness.

How Can I tell if my shocks are failing?

Shocks fail in a few different ways. The most noticeable way is that the oil inside the shock leaks out. This will leave an oily mess on the shock absorber. One of the symptoms of a shock that lost its oil is excessive bouncing. Excessive bouncing is more than Three bounces after hitting a bump.  You will hit a bump in the road and the car will keep bouncing. Another way is the valve inside of the shock will start to fail where it will only allow the oil to flow one way inside the shock. As you drive the shock will become very stiff and it will start to ride like a low rider. Usually the shock gets shorter when this happens and you can see that one corner of the car is lower than the others.

Do shocks just wear out?

Yes. Shocks perform one of the hardest jobs on the car. Every time the car moves up, down or hits a bump the shock is doing its job. The amount of movement really adds up after a while. Most shocks have a useful life of around 100,000 miles or 10 years. After that amount of time and mileage they start to degrade to the point where they affect stopping distance. They then become a safety concern and should be replaced.

My shocks are failing. Which type of shock should I choose?

It depends on what kind of ride you are looking for. If you want your car to handle like a sports car, a Mono Tube Shock is the better choice. If you are looking for comfort, Cadillac ride, using a twin tube shock will be a better choice. I personally went from a Twin Tube design on my truck to a Mono Tube Shock design and noticed that the ride was much stiffer than before. I feel the bumps in the road a lot more when the truck is unloaded and it is a lot smoother when loaded or towing.Ultimately it comes down to how you use your car and what kind of performance you are looking for. If you mostly drive on paved roads and are looking for comfort Twin Tube Shocks are the way to go. If you drive off road or you are looking for a stiffer ride Mono Tube Shocks are the way to go.