Suspension for MAN / Mercedes trucks, buses and vans

The suspension of a MAN or Mercedes truck, coach or van plays a decisive role in driving comfort, stability, safety and the vehicle’s service life. In professional applications, vehicles are confronted daily with heavy loads, varying road conditions and long driving hours. The suspension system ensures that the load is distributed evenly over the axles and the chassis. When suspension components wear or fail, this has direct consequences for other vehicle systems. At Braem you will find a wide range of suspension parts that enable repairs to be carried out reliably, durably and in full technical compliance.

The function of the suspension system within the vehicle

The suspension system carries the weight of the vehicle and its load. It ensures that the chassis does not rest directly on the wheels. For this purpose, among others shock absorbers, air springs, coil springs and leaf spring packs are used. The suspension system absorbs shocks caused by driving through potholes and over traffic bumps. It ensures that the wheels remain on the ground and provides stability so that the vehicle cannot tip or sway. It delivers safety and comfort.

Interaction with chassis and axles

Shock absorbers, coil springs, air springs and leaf spring packs are attached at the bottom to the axle and at the top to the chassis. There are two types of suspension. With leaf suspension on a front axle, a spring pack consisting of leaf springs is mounted in the longitudinal direction of the vehicle. The spring pack is fitted with two spring eyes into which silent blocks are pressed. The front spring eye is fastened with a bolt to a spring hanger mounted on the chassis. The rear spring eye is mounted to the chassis via a shackle. This shackle can move forwards and backwards so that, under higher vehicle load and the resulting lengthening of the spring pack, the spring pack is prevented from breaking. The front axle lies transverse to the vehicle under the center of the spring pack and is connected to it via U-bolts. With leaf-sprung tandem axles, the spring pack is bolted to the axles at its ends. Rubber blocks are mounted between the ends and the axle to absorb vibrations. The spring pack rests in the middle on an equalizer beam, providing an even load distribution over the two axles. This is referred to as a bogie suspension. With air suspension, air springs are used instead of leaf springs to connect the chassis to the axles. The bottom of the spring is mounted on the axle via a piston. The top is connected to the chassis via a plate. To keep the axles in position, they are connected to the chassis by means of radius rods. The suspension works closely with the chassis, the driveline and axles. When spring packs or air springs lose their load-bearing capacity, the vehicle sags unevenly. This causes stress in the chassis and means that forces are no longer distributed correctly. It leads to chassis torsion, which can cause cracks. To prevent the above, stabilizers are fitted to vehicles. In a bend, the vehicle leans due to centrifugal force. These forces are reduced by installing a stabilizer bar (also called a torsion bar). This steel bar connects the left part of the axle to the right part. Due to different axle movements on the left and right, the stabilizer is twisted. This creates a counterforce in the stabilizer that helps the wheels run more evenly again. The axle is stabilized. This stabilizer is attached to the axle by means of brackets and silent blocks, and is connected to the chassis by means of stabilizer links.

Main suspension components

This category includes, among others, leaf springs, air springs, shock absorbers, stabilizer bars, radius rods, rubber components and fasteners. Each part has a specific function in absorbing and distributing forces.

How to choose between air suspension and leaf suspension

Why choose leaf suspension:

It is a very robust system that can handle heavy loads.

It is built with few components that are mainly mechanical, making repairs straightforward and reliability high. It does not generate fault codes, so diagnostic and programming equipment is not required for repair. It is inexpensive to purchase and maintain. It is ideal for rough use on construction sites, poor roads and muddy conditions. This system is chosen when high load capacity, simplicity and heavy-duty work are required.

Why choose air suspension:

Although an air-suspension-based system is more expensive than leaf suspension, it offers many advantages. Driving comfort is higher because the system adapts to varying load due to the cargo. The vehicle ride height remains constant, so the loading platform height always stays at the same level. This is convenient for loading and unloading goods when docking at a loading bay. It is less prone to wear and experiences less wear due to vibrations. The system requires electronic components, making repairs more complex. This system is chosen when driving comfort, stability and varying load conditions are required.

The usefulness of silent blocks for the suspension

Silent blocks (also known as rubber-metal bushings or blocks) form the elastic connections between the various moving and load-bearing suspension components. They absorb vibrations caused by road irregularities, so the chassis is not stressed directly. This dampens movement noise caused by metal-to-metal mounting. They allow limited movement without slack.

Signs and consequences of worn silent blocks (rubber-metal component)

Silent blocks are subject to wear and lose their effectiveness through use. This causes a lot of noise because of friction between metal parts. Ride comfort decreases and the vehicle is subject to vibrations. Road holding deteriorates, requiring the driver to constantly correct while steering. This overloads the steering system. To check the condition of the silent blocks, place the vehicle on a lift or over a service pit and ensure that the suspension is not under stress. Check the rubber for tears or cracks. Check the rubber for elasticity. Dried-out, hardened rubber or overly soft rubber reduces effectiveness. Check the bond between the rubber and the metal. Check for slack by applying mechanical force with a pry bar.

The importance of timely or preventive replacement of suspension parts

Timely replacement of suspension components prevents bigger problems that make repairs even more expensive. It ensures good road holding, so the tires wear less quickly. Poorly functioning shock absorbers cause the wheels to maintain less contact with the road, making the vehicle bounce or continue to oscillate. This reduces the vehicle’s grip on the surface, increasing the risk of rollover. The ABS/EBS system must intervene more and braking distance increases. Timely replacement increases safety. Air springs that leak air increase fuel consumption. The pneumatic control system that guarantees ride height must constantly correct. As a result, the compressor, driven by the engine and providing the required air pressure, must work harder.

Repairing or replacing suspension components

Replacing a spring pack is usually the right choice. With broken leaf springs, replacement is the only solution. Repair would require welding, which changes the metallurgical structure of the material. This reduces strength and changes elasticity, so it no longer meets the manufacturer’s requirements. Vehicles with welded leaf springs will fail inspection and are not allowed on the road. A leaking air spring must always be replaced and cannot be repaired. Worn silent blocks, rubber blocks and shock absorbers must always be replaced. A stabilizer that is broken must be replaced. Suspension components can rarely be repaired.

When replacement is necessary

If repaired parts no longer meet the requirements of the manufacturer and the inspection authorities, replacement is necessary.

Practical advice based on experience in suspension maintenance

Start with a visual inspection.

• Check spring packs for cracks and broken leaves.
• Check air springs for leakage.
• Check the silent blocks for cracks and slack
• Check stabilizers for deformation and poor bushings.
• Check that standard bolts, center bolts, nuts, U-bolts and other fasteners are tight. Use a lift or a service pit for this. On the same axle, the suspension system is identical on the left and right. Check that both sides are symmetrical. Replace the parts on both sides of the axle. Then take a test drive and check the vehicle for handling and unexpected noises.

The added value of Braem for suspension parts

Braem has an extensive stock of suspension parts for MAN and Mercedes trucks, coaches and vans. Thanks to fast delivery and technical support, repairs can be carried out efficiently.

Customers choose Braem because of:

• High quality thanks to thorough quality control
• Technical support during disassembly and assembly
• Fast delivery within Europe and beyond
• Clear warranty and return conditions

A well-maintained suspension not only increases comfort and safety but also extends the service life of the entire vehicle.