Fox 4.0 Factory Series Bypass Piggyback

The price shown here is before the upgrades below. 

This product is currently out of stock and unavailable.

The FOX 4.0 Factory Series Bypass shock is the ideal position-sensitive shock for lightweight unlimited offroad racecars and pre-runners.
Bypass shocks allow precise adjustment of multiple stages of compression and rebound damping. The 4.0 Factory Series Bypass shock adds another competitive option to FOX’s already extensive bypass shock lineup. The expanded volume provides a wider damping range and increased cooling-optimizing the suspension and increasing the vehicle’s capabilities. The 4.0 Bypass shock uses the same extended and compressed lengths as the 3.5 Factory Series Bypass for easy upgrading.
The 4.0 Bypass shock comes standard with FOX’s Rotating Body Cap (RBC) technology that allows quick and easy positioning of the shock body with simple hand tools. RBC eliminates the need of re-clocking body cap threading to achieve shock body rotation for chassis clearance issues. The 1.125″ hard chrome-plated 17-4 H900 stainless steel shock shaft provides increased strength and stiffness.
Multiple stroke lengths are available with a large 3.5 piggyback reservoir and 4 or 5 tube layouts. FOX also offers many custom options to maximize your suspensions performance while adhering to the vehicle’s space restrictions. Options include custom bypass tube layouts, External Cooling Systems (ECS), remote reservoir mounting, and eyelet lengths.


  • • Smooth-bore, clear coated, zinc plated, honed seamless alloy bodies
  • • Black anodized 6061-T6 billet aluminum
  • • 1.25″ hard chrome plated stainless steel 17-4 H900
  • • Race-developed high-flow piston design
  • • Proprietary deburred valve shims
  • • Redundant sealing pack system main seal, wiper seal, scraper seal
  • • High temperature Viton seals
  • • FOX formulated for ultimate performance at variable temperatures
  • • Piggyback
  • • Optional remote reservoir
  • • Lined, heat-treated, alloy steel spherical bearings 5/8″ bolt x 1 1/2″ wide
  • • Rotating Body Cap
  • • Compression bypass adjusters
  • • Rebound bypass adjusters
  • • Nitrogen pressure
  • • Compression valving
  • • Rebound valving
Dimensions 50 × 22 × 10 in
Shocks/ Options

(Sold Individually) 4.0 x 16 Factory Series Bypass (5 Tube) Piggyback, (Sold Individually) 4.0 x 18 Factory Series Bypass (5 Tube) Piggyback


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