Advantages and disadvantages of trailing arm suspension

The trailing arm suspension itself has the disadvantages of non-independent suspension, but it also has the advantages of independent suspension. The biggest advantage of trailing arm suspension is that the distance between the left and right wheels is large, the camber angle of the car body is unchanged, and the shock absorber does not produce bending stress, so the friction force is small. The comfort and maneuverability of the traction arm suspension are limited. When braking, the front wheel of the trailing arm suspension will sink, and the rear wheel will sink to balance the car body, which can not provide accurate geometric control.

Main advantages: simple and practical structure, small occupied space and low manufacturing cost.

Main disadvantages: poor bearing capacity, weak anti-roll ability, poor shock absorption performance and limited comfort.

Applicable models: small and medium-sized cars, low-end SUV rear suspension

Different manufacturers have different names for this kind of suspension, such as: longitudinal arm torsion beam independent suspension, longitudinal arm torsion beam dependent suspension, H-type longitudinal swing arm suspension and so on. In the final analysis, they are all the same suspension structure-trailing arm suspension, but the training is slightly different.

The trailing arm suspension is a suspension structure specially designed for the rear wheels. The structure is very simple-the wheels are rigidly connected with the car body or the car frame through a thick trailing arm that swings up and down, and then the hydraulic shock absorber and spiral spring are used as soft connections to absorb and support the car body, and the left and right wheels are connected with cylindrical or square beams. From the structure of the trailing arm suspension, because the left and right longitudinal swing arms are connected through the cross beam, the suspension structure still maintains the overall bridge type, so that the camber angle of the wheels connected with the longitudinal arm does not change during the dynamic movement, which will make the front wheels understeer, so the trailing arm rear suspension can not provide a good guarantee for the accurate control of the car body. Fortunately, however, the beam connecting the left and right trailing arms can rotate at the joints, which can make the left and right wheels jump freely in a small space to a certain extent without disturbing the other wheel.

Having said that, we need to use the actuation principle of trailing arm suspension to see why its performance is so dull. As we said before, the trailing arm suspension is connected by a cross beam, so it is similar to the full-bridge suspension in some characteristics. For example, suppose a small car with a trailing arm and rear suspension passes through a short-wave road. Because the left and right rear wheels are connected by a cross beam, the wheels on both sides will shake with the uneven road surface at the same time. Although the hydraulic shock absorber and spiral spring can absorb part of the vibration, due to the integrity of the rear suspension, the residual vibration that cannot be filtered will inevitably be transmitted to the car, so the passengers will feel some discomfort. This discomfort is more direct. If the rear wheels are equipped with multi-link suspension at this time, the left and right rear wheels can move up and down through their respective links, and they will not interfere with each other because of the center sill, so the comfort will be greatly improved.

Comfort is like this. In terms of handling, you can't expect the trailing arm to bring you great surprises. In dynamic motion, especially in high-speed steering, the car body will roll because of inertia. As mentioned above, the camber angle of the wheel connected to the longitudinal trailing arm will not change during steering, which will lead to understeer of the front wheel. Therefore, the trailing arm suspension gives people the impression that the handling under extreme control is poor and the rear wheel reacts slowly. In fact, this is also related to the connection of the left and right trailing arms (wheels) through the cross beam, because the car body will roll when turning, and the wheels inside the corner will try to keep in contact with the ground under the tension of shock absorbers and springs, and uneven stress on the left and right wheels will affect dynamic handling. There are two solutions to this problem, one is to replace the more advanced multi-link suspension, and the other is to introduce the rear wheel follow-up steering function.

Although the shortcomings and physical defects of trailing arm are obvious, the focus of contradiction is that it also has the same outstanding advantages: it occupies a small space of the car body, so that the camber angle of the car body will not change during movement, and the shock absorber will not bend under force to aggravate tire wear.