What Are Car Undercarriage Parts? What Are Their Functions?

While most car users focus on the vehicle's engine power, fuel consumption, or exterior appearance, there is another system that is just as important for safe and balanced driving: the undercarriage. This system, which is in contact with the road and directly affects driving dynamics, is critical for driving safety and comfort.

In this article, we will take a detailed look at what the car's undercarriage parts are, what each one does, and why it is so important for this system to function properly. We will also explain the names and functions of car parts that people are curious about, with examples.

The undercarriage is the general name for all the mechanical parts that connect the wheels to the body of the vehicle. These parts include the suspension system, steering system, and running gear. The undercarriage enables the vehicle to grip the road, directly execute the driver's commands, and absorb shocks from the road.

The undercarriage system is a structure that is not commonly known like the engine, transmission, or brakes, but is central to safety.

• Shock Absorber
• Coil Springs
• Knuckle and Knuckle Head
• Control Arm
• Z-Arm (Balance Arm)
• Anti-Roll Bar (Stabilizer Bar)
• Axle and Axle Head
• Carrier (Porya)
• Tower Bushings
• Chassis
• Transmission
• Shaft
• Differential
• Axle
• Brake Pad
• Exhaust System

The chassis is the basic carrier system that forms the skeleton of the vehicle and to which all other parts are mounted. Many important parts, such as the engine, suspension, and transmission, are directly connected to the chassis. It also ensures structural integrity by increasing the vehicle's torsional strength. Damage to the chassis can adversely affect all of the vehicle's performance and safety systems.

The transmission system transfers the power generated by the engine to the wheels in a controlled manner. Gear shifts allow for different speed and torque requirements to be met. Transmissions, which are divided into automatic and manual types, are one of the most important systems that determine the driving character of the vehicle. The proper functioning of the transmission is of great importance in terms of the functionality of the undercarriage system.

The shaft is a rotating shaft that connects the engine and differential to transmit drive power. It is used especially in rear-wheel drive or four-wheel drive vehicles. The shaft, which rotates at high speeds, must operate smoothly and without vibration; otherwise, serious instability and noise problems may occur in the vehicle. Damage to the shaft system directly affects traction and fuel efficiency.

The differential is a transmission component that balances the rotation speeds of the wheels and enables the vehicle to take corners smoothly. The differential, which meets the independent rotation needs of each wheel, is indispensable for stability and road holding, especially when turning. Differential failures can cause traction loss and the risk of skidding in the vehicle.

The axle is an axle system that connects the wheels and carries the load of the chassis. Vehicles have front and rear axles. Acting as the backbone of the running gear, axles also work with the suspension system to help reduce vibration. Problems such as bending or cracking in the axle pose serious risks in terms of both safety and wheel alignment.

Brake pads are components within the brake system that slow down the vehicle by rubbing against the brake disc. They directly affect the braking power of the undercarriage. Worn or low-quality brake pads increase braking distance and compromise driving safety. Brake pad inspection is especially critical for vehicles operating under heavy loads.

The exhaust system expels waste gases generated in the engine combustion chamber. It is located at the rear of the undercarriage and extends outward from beneath the vehicle. It also reduces noise levels and filters harmful gases. Leaks or holes in the exhaust system can cause both environmental and mechanical problems.

Shock absorbers are components that absorb vibrations and impacts between the wheels and the vehicle body. They come into play especially on rough roads or when driving at high speeds, improving road holding and maintaining driving comfort. Shock absorber failure can lead to increased braking distances, vehicle swaying, and a fatiguing driving experience.

Coil springs, working in conjunction with shock absorbers, distribute the vehicle's weight evenly, ensuring the body remains balanced. They reduce the impact of bumps on rough roads. They play a particularly important role in maintaining ground clearance in loaded vehicles.

The steering knuckle is the rod that transmits movement from the steering wheel to the wheels. The tie rod end is located at the end of this rod and provides flexibility for maneuverability. These parts ensure that the driver's steering commands are transmitted to the wheels accurately and quickly. Worn tie rod parts can cause the steering to feel loose or cause the vehicle to veer off course even when driving straight.

Control arms are metal parts that connect the wheel to the chassis and allow suspension movement. Usually triangular in shape, control arms balance both vertical and horizontal forces. If they malfunction, the vehicle may experience knocking noises, tire wear, and directional instability.

The Z-bar is a stabilizing element that connects the right and left suspension systems, preventing body roll during turns. The Z-bar controls weight transfer when entering turns and maintains the vehicle's stability. Loosening or breaking of this part can cause an unstable feeling while driving.

The stabilizer bar extends horizontally between the two wheels of the vehicle. It reduces body roll when the vehicle is cornering. This improves road holding and ensures driving safety. Without this part, the vehicle leans excessively when turning, increasing the risk of skidding.

The axle is the main component that transmits engine power to the wheels. Axle heads are located at the ends of this component and provide flexibility. They are particularly important for turning ability in front-wheel drive vehicles. A faulty axle can cause vibration, loss of traction, and rattling noises in the vehicle.

The hub is the part that connects the wheel to the body and works in conjunction with the brake disc, drum, and bearings. It is also one of the points that carries the weight of the vehicle. If the hub bearings fail, a humming noise may occur while driving.

Tower bushings are located between the shock absorber and the vehicle chassis. These parts prevent suspension movements from being transmitted directly to the cabin. They provide vibration, noise, and shock isolation. Worn tower bushings can produce metallic knocking sounds while driving.

If your vehicle exhibits the following symptoms, there is likely a problem with the suspension system:

• Play or stiffness in the steering wheel
• Clunking or metallic noises when driving on rough roads
• The vehicle pulling to the right/left during braking
• Feeling of loss of control when cornering
• The vehicle failing to hold its direction even on a straight road
• Irregular tire wear

Failure of the undercarriage to function properly can also cause extra load on other car parts.

Suspension parts should be checked at specific intervals and replaced if necessary. This interval should be shorter, especially for commercial vehicles. The generally recommended check intervals are as follows:

• Shock absorbers and springs: Every 20,000–30,000 km
• Rot, swing arm, Z-rot: Every 15,000 km
• Axle and hub bearings: Should be reviewed during each periodic maintenance
• Wheel alignment and balancing: Should be performed every 10,000 km

Undercarriage inspection is an integral part of a vehicle's overall mechanical evaluation.

One of the important issues to consider when renting a commercial vehicle is the mechanical health of the vehicle to be rented. DRD Fleet Rental regularly checks the undercarriage systems of every vehicle in its fleet and performs periodic maintenance throughout the period of use.

Our vehicles are meticulously inspected not only for their external appearance but also for all important car parts in terms of safety and performance. Click now to get a long-term vehicle rental offer.