Pushrod Suspension Parts: A Comprehensive Guide

Pushrod suspension is a type of linkage system used in race cars, high-performance sports cars, and certain off-road vehicles. It offers advantages in terms of packaging, aerodynamics, and adjustability. If you're building or upgrading a pushrod suspension, understanding the individual parts is critical. Here's a breakdown of the core components and what to consider when selecting them.

Key Pushrod Suspension Parts

The pushrod system consists of several key parts that work together to control wheel motion and damping. Each component plays a specific role in the system's performance.

Pushrods

The pushrod itself is a rigid rod that connects the lower control arm (or upright) to the bell crank. It transmits compression forces from the wheel to the damper assembly. Pushrods are typically made from chromoly steel or aluminum alloy, depending on the application. Chromoly offers high strength and durability for racing, while aluminum reduces unsprung weight. Pushrod length must be precisely matched to the vehicle's geometry.

Bell Cranks

Bell cranks are rocker arms that pivot on a chassis-mounted shaft. They receive the pushrod force and convert it into a motion that compresses the damper. Bell cranks come in various shapes and leverage ratios. The ratio determines how much damper travel corresponds to wheel travel. Common ratios range from 1:1 to 2:1. Higher ratios provide more damping force for a given wheel movement but require stronger dampers.

Dampers (Shock Absorbers)

In a pushrod system, the damper is mounted remotely – often horizontally or at an angle – and actuated via the bell crank. This allows for more flexible damper placement and easier access for adjustment. High-quality dampers are essential. Look for adjustable damping (compression and rebound) and proper valving for your spring rates. Many pushrod setups use coilover dampers where the spring sits over the shock body, but separate springs and dampers are also common.

Springs

Springs in a pushrod system may be coaxial with the damper or separate. The spring rate must match the bell crank ratio to achieve the desired wheel rate. For example, a 2:1 bell crank ratio means the spring rate needs to be roughly four times the desired wheel rate (since force is multiplied by the square of the motion ratio). Coil springs are typical, but torsion bars or air springs are used in some applications.

Anti-Roll Bars (Sway Bars)

Many pushrod suspensions incorporate an anti-roll bar to control body roll. The bar connects left and right bell cranks or pushrods, often via short links. The bar stiffness can be adjusted by changing bar diameter or using adjustable blade arms. Proper anti-roll bar selection is crucial for balancing cornering grip.

Mounting Brackets and Hardware

All parts need sturdy mounting brackets. Bell crank brackets bolt to the chassis, and damper mounts must be aligned correctly. Use high-grade hardware (e.g., 12.9 grade bolts) and proper locking mechanisms like safety wire or Nylock nuts. Spherical bearings or rod ends are common at pushrod and bell crank connections to reduce friction and allow free movement.

Materials and Manufacturing

Pushrod suspension components are exposed to high loads and harsh environments. Material choice affects weight, durability, and cost.

• Chromoly Steel (4130): Strong, fatigue-resistant, and weldable. Common for pushrods and bell cranks in race cars. Heavier than aluminum but more affordable.
• Aluminum Alloy (7075-T6 or 6061-T6): Lighter, good for reducing unsprung weight. Used for pushrods and bell cranks in pro-level and high-budget builds. Requires careful design to avoid flex.
• Titanium: Extremely strong and light, but very expensive. Used in F1 and top-tier motorsports.
• Stainless Steel: Sometimes used for hardware or pushrods in corrosive environments.

Machining processes include CNC milling, turning, and heat treating. For off-the-shelf parts, check for proper surface finishes (e.g., anodized aluminum or black oxide steel) to resist wear.

Common Applications

Pushrod suspension parts are most common in:

• Open-wheel race cars (Formula, IndyCar): where aerodynamics and low hood height matter.
• Sports cars (e.g., Ferrari, McLaren, Corvette Z06): some production cars use pushrod or similar linkage systems to improve packaging.
• Off-road racing trucks and buggies: pushrod setups allow high wheel travel and easy damper tuning.
• Kit cars and custom builds: enthusiasts often choose pushrod suspension for adjustability and cool factor.

If you're building a street car, consider that pushrod systems can be more maintenance-intensive than conventional McPherson struts or double wishbones.

Installation and Maintenance Tips

Proper installation is crucial for safety and performance.

• Geometry Check: Before finalizing, use a suspension simulation or on-car alignment tool to verify motion ratios and bump steer.
• Bearing Preload: Spherical bearings and rod ends should be tightened without preload – they need to pivot freely. Use shims if necessary.
• Lubrication: Apply anti-seize or lithium grease to threads and bearing surfaces to prevent galling.
• Clearance: Check that no parts contact each other or chassis at full compression and rebound.
• Maintenance: Inspect rod ends for play, check pushrod straightness, and retighten mounting bolts periodically. Replace worn components immediately.

Choosing the Right Parts

When buying pushrod suspension parts, focus on fit, material, adjustability, and reputation of the manufacturer.

• Fitment: Ensure pushrod length and bell crank mounting pattern match your chassis. Many manufacturers offer custom lengths.
• Adjustability: Adjustable bell cranks (with multiple mounting holes) allow fine-tuning of motion ratio. Choose a damper with adjustable damping.
• Quality: Look for parts from established motorsport suppliers. Avoid cheap no-name parts that may fail under load.
• Support: If you're new to pushrod suspension, consider buying a complete kit with instructions or consulting an expert.

Final Recommendation

If you're just getting started with pushrod suspension, purchase a matched set of pushrods, bell cranks, and dampers from a reputable brand like QA1, AFCO, or Penske. These manufacturers offer technical support and replaceable components. For a custom build, work with a suspension engineer to calculate required ratios and spring rates. Invest in quality hardware and spherical bearings – they are the backbone of the system. With proper selection and setup, a pushrod suspension can significantly improve your vehicle's handling and adjustability.