April 20, 2021

Bypass Shocks PART 1

  • How do Bypass Shocks Work?
  • Shock Zones & Basic Tube Layout
  • Bottom Take Off Reservoir

Bypass Shocks PART 2

  • Off the Shelf Options
  • Multiple Compression & Rebound Tubes
  • Staggered vs Overlapping Tubes
  • Piggyback vs Remote Reservoir

Bypass Shocks PART 3

  • Custom Setup Recommendations
  • Shock Diameter
  • Tube Layout around body
  • Tube Heights & Diameter

Bypass Shocks PART 4 

  • Fox vs King Comparison
  • Check Valve Design
  • Pistons
  • Bypass Adjusters Screws
  • Piston Rods
  • Oil Seals


Bypass Shocks PART 5

  • Bypass Shock Setup
  • Up Travel
  • Motion Ratio – Coilover and Bypass
  • Total Weight
  • Weight Distribution (front/rear)
  • Unsprung Weight


Quickly recapping what has already been covered. King performance series bypass shocks are a cost conscious product line that uses smaller than standard tubes in a staggered layout. King Race Series and Fox Factory Series bypass shocks use larger tubes in an overlapping configuration. In 2.5” diameter Fox Factory Series and King Race Bypasses flow 3x as much oil as King Performance Series, making them much more tuneable.

Bypass Check Valve

King Performance Series are built with cost in mind and come standard with a plastic check valve. This valve is not suitable for hard use or racing and commonly gets stuck in the tube. Steel valves are available for an additional price.

Note: we do not recommend the steel valves with rubber tips, the rubber usually fails and breaks apart.

King Race Series bypass shocks are designed for racing. The King Race design has proven to be successful at the track, but there are a few tricks to keep in mind. King uses stainless steel for the plunger and the check spring. Stainless steel is corrosion resistant, but loses a lot of strength at high temperatures. As a result we recommend replacing the springs on every rebuild if you’re racing or getting them hot. The long stem on the King bypass valve is also prone to breaking if the tubes are run wide open, we recommend running the tubes at least two turns closed, or replacing them during frequent rebuilds.

Fox Factory series bypasses use a simple design with a tapered seat which helps make them quieter than others. Fox uses carbon steel springs which don’t need to be replaced as frequently.


Fox offers several pistons for each size bypass shock depending on whether you need high flow or low flow for your particular application. Having a wide range of pistons to choose from is nice when tuning a wide variety of vehicles and setups.

Adjusting Screws

King Performance Series and Race Series bypass shocks use the traditional screw and jam nut to control the location of the plunger. With this design the adjusters can be easily set to any position, but it is necessary for the tuner to carefully track how far they turned the screw. Fox Factory Series uses spring loaded detents to provide ¼ turn increments in the ¾” tubes, and 1/8 turn increments for 1” tubes.


King uses chromoly shafts in both Performance Series and Race Series, but they are not surface hardened. As a result the surface is softer than industry standards and more prone to nicks and dings. We recommend running boots on all bypass shocks to increase their longevity.

Fox uses stainless steel shafts that are nearly twice as hard and twice as strong as King. Even with these tough shafts, it is a good idea to run boots or shaft guards.


King Performance Series Bypasses come standard with NBR seals. King Race Series and Fox Factory Series come standard with Viton which is a lot more durable at high temperatures.

There are other differences between the shocks covered in this article, but they are not necessarily items that should be the deciding factor in which shocks you purchase.


Fox and King both make high quality racing shocks which are proven industry leaders in competition. The differences in materials and components are an important part of the shocks and should be taken into consideration along with tube layout and tube size.

  • Shock Diameter
  • Tube Layout around body
  • Tube Heights & Diameter
  • Custom Setup Recommendations

Release Date: May 4th

  • Bypass Shock Setup
  • Up travel
  • Motion ratio – coilover and bypass
  • Total weight
  • Weight distribution (front/rear)
  • Unsprung weight