MacPherson Strut, Double Wishbone And Solid Axle: Dependent And Independent Suspension Systems

Broad classification of suspension systems includes MacPherson Strut, Double–Wishbone and Solid Axle setup. The passenger car segment uses independent suspension setups mounted at each wheel. The purpose of a suspension unit in a car is to provide a cushion between the road and the car cabin. It must also gobble up the road vibrations and well as sudden thuds due to potholes. It must ensure a comfortable ride for the passengers. Providing stability and good handling around the corners is also the job of suspension. Let us look at each type of suspension in-depth:

MacPherson Strut Independent Suspension

The most widely used independent suspension system is the MacPherson Strut. Almost every passenger car today has this setup at the front and a simpler coil spring at the rear. MacPherson Strut includes a simple assembly of coil spring and a damper/shock absorber. The task of the spring is to store the energy from a sudden jerk from the road. The damper uses hydraulic fluid to dissipate this energy in form of heat. Together they restrict any unwanted movement of the car because of undulations on the road.

Independent MacPherson Strut Suspension

Image Source: CarTreatments

Pros and Cons of MacPherson Strut

  • One of the biggest advantages that this setup offers is that it leaves a lot of space around the wheel hub open. This space is where the driveshaft is located.
  • Cost-effectiveness and ease of maintenance are key features of this suspension setup.
  • Reliability because of lesser number of parts.
  • Less weight because of fewer components.
  • It requires a monocoque/unibody design because the strut attaches directly to the vehicle body.
  • Because of the same reason, it is not the best around the corners.
  • It is not used in off-road vehicles because of the limited movement of the strut.

Double Wishbone Independent Suspension

As the name suggests, Double Wishbone or Double-A suspension setup has the shape of a bone found in birds. It is also an independent setup and has two A-shaped control arms. These control arms connect to the wheel and frame of the vehicle at either end. One arm is generally shorter than the other one. As a result of this, during cornering, the tyre remains in contact with the ground because of camber gain.t doesn’t directly connect to the chassis, it is very flexible especially around the corners. The spring and damper placement are also very flexible according to the availability of space.

Independent Double Wishbone Suspension

Typically, this suspension system is found in higher-end luxury cars. A number of vehicles also use this setup in off-roaders because the travel of the suspension setup is long and it can take care of larger bumps and potholes with ease. If comfort and handling is your priority, Double Wishbone setup is one of the best suspension systems out there at the moment.

Pros and Cons

  • Double control arms allow for great stability and handling around the corners by making sure that the tyres remain in contact with the surface.
  • Although it involves double arms in the setup, the overall setup is quite compact and flexible allowing for a lot of empty space around for something else.
  • Because the control arm is not connected to the car directly, off-roading becomes easy because of long suspension travel.
  • The main disadvantages that don’t allow this technology in all cars are cost and complexity.
  • It involves more number of parts which are a bit difficult and time-consuming to maintain.

Also read: This Verna to get air suspension in India

Solid Axle Dependent Suspension

Solid Axle setup is the most common in heavy duty vehicles. It is found at the rear and is a solid bar connecting the two axles. It is therefore a type of dependent system. The weight of the entire truck rests on solid axle because it is very rigid and tough. Broadly speaking, there are three types of solid axle suspensions:

Leaf Springs

These are the most common spring for heavy-duty vehicles overall. It is fairly simple in construction, cheap to manufacture and does a good job. Leaf springs comprise of a number of metal plates, one of top of the other. These then connect to the solid axle of the truck parallel to the ground to get maximum work done.

Dependent Suspension Leaf Spring

The disadvantage of leaf springs includes free movement of the spring sideways as well as forward and backward. The unsprung mass is increased because they are very heavy.

Trailing Control Arm

Trailing Control Arm negates the disadvantage of leaf spring in that it is connected to the solid axle and chassis. Resultanlty, it prevents the sideways and forward and backward movement of the suspension. The construction is very simple as it involves on two additional control arms. They are strong and durable as well, although a bit heavy like the leaf springs.

Dependent Suspension - Trailing Arm

Image Source: Rapid Racer

Panhard Rod

Panhard Rod is nothing but a rigid bar running across the rear of the vehicle to prevent sideways movement. The ends connect to the chassis and solid axle n either side. They are also not expensive to manufacture or difficult to install. They can also be used in combination with trailing arm to compensate for its downside.  

Dependent Suspension - Panhard Rod

Image Source: Vorschlag