What does the running gear consist of?

The running gear of a vehicle consists of the components that enable movement, support the vehicle’s weight, and ensure stability and control. It includes the suspension system, wheels, tyres, brakes, and drivetrain (axles, differential, and transmission in some configurations).

1. Suspension system: Comprised of springs, shock absorbers, and linkages, it absorbs road shocks and maintains tyre contact with the surface.
2. Wheels and tyres: Provide traction, support the vehicle’s load, and influence handling. Alloy wheels are common for their balance of strength and weight.
3. Brakes: Disc or drum brakes slow or stop the vehicle, with modern systems often including ABS (anti-lock braking).
4. Drivetrain: Transfers power from the engine to the wheels. In front-wheel-drive cars like the Ford Focus, this includes CV joints and driveshafts.

The running gear directly impacts ride comfort, handling, and safety. For example, a well-tuned suspension in a BMW iX ensures smooth motorway cruising, while high-performance tyres on a Tesla Model 3 improve grip. Regular maintenance, such as checking tyre pressure and brake wear, is essential for longevity.

The running gear of a motor vehicle typically comprises four main components: the frame, axles, suspension, and wheels. The frame serves as the foundational structure for the entire vehicle assembly, with the axles connected to the frame via the suspension system, and the wheels mounted on the axles.

The primary function of the running gear is to integrate the vehicle into a cohesive unit, support its total mass, transmit torque from the drivetrain, and generate tractive force through the interaction between the driven wheels and the road surface.

The frame is a bridge-like structure connecting the various axles and forms the mounting base for the entire vehicle. The axles facilitate the transmission of forces in all directions between the frame (or monocoque body) and the wheels.

Axles are categorised into four types: steering axles, drive axles, steering drive axles, and dead axles. Wheels are rotating components that carry tyres on their exteriors, mount onto axles at their centres, and bear the vehicle's load - consisting of a hub, rim, and spokes.

Wheels are principally divided into disc-type and spoke-type variants. The vehicle suspension system collectively refers to all power-transmitting linkage devices between the frame and axles. This system elastically connects the axles to the body, dampening impact forces from uneven road surfaces during travel to ensure passenger comfort and cargo integrity.

From an engineering perspective, the running gear is the backbone of a vehicle’s dynamics. It integrates the suspension (MacPherson struts or multi-link setups), steering linkage, and braking components. Engineers focus on optimising these elements for balance—stiffness for cornering, compliance for comfort. For instance, the Nissan Leaf’s regenerative braking system is part of its running gear, blending deceleration with energy recovery.