Torsion bar suspension of a car: the principle of operation

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:42

The automotive industry is developing at a rapid pace. Every year, companies come up with new systems and technologies. Today, everyone is used to cars with independent multi-link suspension. But not so long ago, cars were produced only with torsion bar suspension (Renault is no exception). What is it and how does it work? Consider in our today's article.

Characteristic and device

Torsion suspension is a type of suspension where torsion bars perform the function of a working element. What are these elements? The torsion bar is a metal mechanism that acts on twisting. It consists of plates or rods of round (rarely - square) section. These plates work together for twisting. The torsion bar can be used as an auxiliary device (as a stabilizer bar) or as an elastic element. The element is attached to the hub assembly of the wheel and passes in the form of a rubber-metal hinge to the hinge assembly. Sections of torsion bars performthe role of suspension arms.

The beam itself can be used longitudinally or transversely. The latter option is used most often on cars. The longitudinal version is found on trucks. But regardless of the type of location, the beam is designed to correct roll when turning and increase smoothness when passing bumps.

In general, the system consists of the following elements:

• Drive.
• Brake disc.
• Lower and upper arm.
• Mosta.
• Torsion.
• Beams.
• Roll bars.
• Shock Absorber.

How does it work?

The principle of operation of the torsion bar suspension is very simple. So, the ends of the beam are rigidly attached to the body or frame of the car (if it is a car or a truck). When moving, a twisting force acts on the beam. In this case, the shaft seeks to return the wheel to its place. If it is installed with an additional electric motor, the driver may be able to adjust the stiffness of the suspension. Thus, the operation of a torsion bar suspension is similar to a spring or sprung suspension. The system performs several tasks:

• Adjusts the bank angle in a turn.
• Provides a smooth ride.
• Absorbs vibrations from wheels and frame.
• Produces wheel stabilization.

Where does it apply?

This suspension can be found on old frame SUVs. These include the Mitsubishi Pajero, as well as the American Suburbans and Tahoe. On passenger cars, such a suspension schemepractically never used (in the days of the USSR, such a design was used on the Zaporozhets). Among the famous foreign cars, it is worth noting the Renault Laguna and the Peugeot 405. It was difficult and expensive to use a multi-link suspension then, and a torsion bar suspension provided a high ride smoothness.

Benefits

Among the advantages of a torsion bar suspension of a car, it is worth highlighting the ease of operation. So, the system is arranged very simply, which makes it easy to carry out repairs and maintenance. Also, this suspension can be adjusted for stiffness. A car enthusiast can independently increase the torsion bars to suit his driving style, make the chassis softer or stiffer.

The next advantage concerns mass. This suspension weighs much less than its counterparts. At the same time, it is small in size. This feature allowed the use of torsion bar suspension on Peugeot and other small cars.

One of the most significant advantages is reliability. Such a chassis practically does not require repair. And if this is a torsion bar suspension of a trailer, then it is completely eternal. Over the entire period of operation, the owners were faced only with the need to adjust the stiffness.

Features

Among other features it should be noted the possibility of adjusting the clearance. Such an opportunity is not on every modern car. At the same time, one key was used to adjust the ride height. It was necessary to unscrew or tighten the necessary adjusting bolt inside the cross beam. When lifting the lever, the vehicle's clearanceincreases. When lowered, the ground clearance decreases. As practice shows, the clearance can be changed by 5-7 centimeters.

Flaws

Now let's note the disadvantages of the torsion bar suspension. They are quite serious, and therefore such a system is no longer used on cars. So why is torsion bar suspension a thing of the past?

The first problem is the oversteer of the car. Compared to modern multi-link counterparts, this undercarriage only slightly reduces roll. It is very difficult to keep such a car at speed. This is especially true of frame SUVs, which have a high center of gravity and a huge curb weight.

The next drawback is the constant vibrations that are transmitted to the body and to the frame in case of bumps. This is especially felt by the rear passengers. Such a suspension cannot be called comfortable.

Next is the needle bearings. They are an integral part of the torsion shaft. The resource of these bearings is 70 thousand kilometers. The elements are protected by gaskets and rubber seals, however, due to the constant exposure to aggressive environments, these seals crack. Dirt and water seep through them. As a result, the bearing fails. This flares the beam seats. This phenomenon contributes to the change of the wheel shaft. If you start the problem, you will have to completely change the beam.

About renovation

Since this suspension loses elasticity over time,vehicle clearance is reduced. To restore it to factory values, you need to adjust the suspension with a key. Also, repair operations include replacement:

• Rear Beam Torsion Bars.
• Rear beam arms.
• Needle bearings.
• Rear beam pins.

In the event of a major overhaul of the beam, it is required to dismantle the torsion bars. So that there are no problems during assembly, you must first outline the position of the torsion bar on the beam. To remove the torsion bar itself, you need to remove it from the spline connection. To do this, you need an inertial puller. Sometimes it is necessary to clean the threads on the spline connection. This section turns sour, and it is not so easy to dismantle the torsion bar.

When repairing such a suspension, needle bearings are most often replaced. This requires extracting the following elements:

• Rear beam arms.
• Torsion.

There are two bearings in the system (one on each side). The problem is that it is impossible to determine the he alth of the element on its own. And further operation of a beam with a worn bearing leads to irreversible wear of the axle. Repair of the rear beam lever is the most difficult operation. It is performed on a special turning and boring machine. You cannot do this work on your own. This requires skill and knowledge.

And find a good specialist in the field with the right equipmentpretty hard.

Pay attention

Before you adjust this suspension, you should run a chassis diagnostic. Often on older cars there are hidden defects in the chassis. It is they who affect the operation of torsion bars. You should also check the alignment. Torsion bars will rise to the desired height only when the angles are correct. Otherwise, the owner will face such a problem as zhor rubber tread. You should also change the distance from the center of the front axle to the edge of the wing. This parameter should be about 50 centimeters. If everything is fine, you can start setting up. The adjusting bolt itself is located in the center and is slightly recessed into the frame.

Instead of a conclusion

So, we found out what a torsion bar suspension is. As you can see, it has both positive and negative sides. But no matter how reliable it may be, most automakers prefer spring independent suspension. Now its resource has become no less than that of the torsion bar. And the level of comfort is incomparable.