Push Rod Suspension Parts: A Complete Guide to Components and Function

Push rod suspension is a sophisticated design commonly found in race cars and high-performance road vehicles. Unlike conventional MacPherson strut or double-wishbone setups, a push rod system uses a pushrod (a slender link) to transfer forces from the wheel to a rocker arm, which then actuates a horizontally mounted damper and spring. This configuration allows for more precise control and packaging benefits. Understanding the individual parts is essential for anyone building, maintaining, or upgrading such a system.

Key Components of Push Rod Suspension

Pushrods

The pushrod itself is a lightweight, rigid metal rod that connects the lower control arm or upright to the rocker arm. It pushes (or pulls, depending on geometry) the rocker when the wheel moves. Pushrods must be strong enough to handle high loads yet light to minimize unsprung weight. They are usually made from steel or aluminum alloy and often feature spherical rod ends for articulation.

Rocker Arms

Rocker arms are pivot-mounted levers that receive force from the pushrod and transfer it to the damper and spring. They can be designed with varying ratios to adjust motion ratio and damping characteristics. Rockers are typically machined from billet aluminum or formed from steel plate. They must have low friction pivot bearings (often needle or ball bearings) for consistent action.

Dampers (Shock Absorbers)

In a push rod system, the damper is usually mounted horizontally or at an angle, inside the chassis or bodywork. This lowers the vehicle's center of gravity and reduces unsprung mass. Push rod suspensions often use high-performance coilover dampers with adjustable rebound and compression damping. The damper's stroke must match the rocker ratio to ensure proper suspension movement.

Springs

Coil springs are typically paired with the damper in a coilover unit. The spring rate and preload are critical for ride height and handling. Some systems use dual springs to control both low-speed and high-speed impacts. Springs must be chosen based on vehicle weight, intended use (track or street), and desired suspension frequency.

Anti-Roll Bars

Anti-roll bars (sway bars) can be integrated into push rod suspension by connecting the rocker arms or pushrods with a torsion bar. This helps reduce body roll during cornering. The bar’s stiffness can be adjustable in competition applications.

Bellcranks and Linkages

While rocker arms are the primary pivot, some designs use additional bellcranks or linkages to redirect forces. These are especially common in inboard suspension setups where space is limited.

How Push Rod Suspension Works

When the wheel hits a bump, the upright moves upward, pushing the pushrod. The pushrod pushes the rocker arm, which rotates around its pivot. The other end of the rocker arm compresses the damper and spring. The motion ratio (distance the damper moves vs. wheel travel) is determined by the rocker geometry. This allows engineers to fine-tune bump and droop characteristics independently. The result is a highly tunable suspension that maintains consistent tire contact.

Benefits of Push Rod Suspension

• Lower unsprung mass: Because heavy components like dampers and springs are mounted inboard, the wheels and suspension arms are lighter, improving responsiveness.
• Reduced aerodynamic drag: Compact packaging allows for cleaner bodywork and better under-car airflow.
• Tunable kinematics: Rocker ratios can be adjusted without changing the entire suspension geometry, enabling quick setup changes.
• Better heat management: Dampers and springs are shielded from radiant heat from brakes and tires.

Common Applications

Push rod suspensions are standard in Formula One, IndyCar, and many sports prototype race cars. They are also used in some high-end road cars like the Chevrolet Corvette (C8) and certain McLaren models. Aftermarket specialists offer push rod conversion kits for track-focused builds.

Choosing Push Rod Suspension Parts

Material Considerations

Components must withstand high cyclic loads. Aluminum pushrods are lighter but may require larger diameter to avoid buckling. Steel pushrods are heavier but more robust. Rocker arms should be of aerospace-grade aluminum with reinforced pivot areas. Spherical bearings should have Teflon liners for low maintenance.

Compatibility

Parts are often vehicle-specific. Rocker ratios and pushrod lengths must match the chassis geometry. It is critical to order components designed for your exact make and model, or work with a custom fabricator.

Adjustability

Look for rocker arms with multiple pivot points or adjustable pushrod ends. This allows fine-tuning of ride height, motion ratio, and spring preload. Dampers with external adjustment knobs (for rebound and compression) are standard in performance applications.

Maintenance

Spherical bearings and pivot points should be regularly cleaned and lubricated. Check for play in rod ends and rocker pivots. Pushrods should be inspected for bending or fatigue cracks.

Push Rod vs. Pull Rod Suspension

A related design is pull rod suspension, where the link is under tension instead of compression. Pull rods can improve packaging further but add complexity. Push rod is more common due to simpler mounting of springs and dampers.

Final Recommendation

For a dedicated track car or a serious performance upgrade, push rod suspension delivers superior handling. Focus on quality components from reputable manufacturers like JRZ, Öhlins, or Penske. If you are new to the system, consult a suspension specialist to ensure correct geometry and setup. Start with adjustable rocker arms and high-resolution dampers to get the most out of the tuning potential. Remember to factor in ongoing maintenance for spherical joints and bearings.