Fox Racing Shocks 981-02-393 4.0 Factory Series Bypass Piggyback Reservoir Shock 18.0 in. 5-Tube Normal Valving Black/Zinc

The Fox Racing Shocks 981-02-393 is a 4.0 Factory Series Bypass Piggyback Reservoir Shock engineered for extreme off-road performance. Built around a massive 4.0-inch main body diameter with a 1-1/8 in. hard-anodized aluminum shaft, this shock delivers superior damping control and durability in the most demanding terrain.

The 5-tube bypass design — featuring 3 compression and 2 rebound bypass zones — allows precise, position-sensitive damping tuning. As the shock moves through its travel, each bypass tube transitions the damping characteristics, providing a plush ride in the initial stroke and firm, progressive resistance as the shock approaches full compression. This makes it ideal for high-speed desert racing, rock crawling, and serious overlanding builds.

The integrated piggyback reservoir provides increased fluid and gas capacity for consistent fade-free performance under repeated high-intensity cycling. Normal valving is pre-configured from the factory for a broad range of applications and load conditions.

Key Features:

• Main Body Diameter: 4.0 in.
• Shaft Diameter: 1-1/8 in.
• Stroke: 18.0 in.
• Extended Length: 46.54 in.
• Collapsed Length: 28.54 in.
• Bypass Configuration: 5-Tube (3 Compression / 2 Rebound)
• Valving: Normal
• Reservoir Style: Piggyback
• Finish: Black/Zinc
• Fox Racing Shocks Factory Series quality construction
• Position-sensitive damping for terrain-adaptive performance
• High-capacity piggyback reservoir for consistent, fade-resistant damping

The Fox 4.0 Factory Series Bypass shock is a race-proven solution trusted by professional off-road racers and serious enthusiasts. Whether built for a prerunner, trophy truck, or purpose-built off-road vehicle, the 981-02-393 delivers the performance and reliability that Fox Racing Shocks is known for worldwide.