The FOX Difference Between Speed and Position-Sensitive Damping
So what’s the deal with speed-sensitive damping and how is it different from position-sensitive damping? All shocks apply speed-sensitive damping, but position-sensitive damping is a game changer. It adds benefits in addition to the ones that speed-sensitive damping provides. Check out the video below to get a quick overview.
Speed-Sensitive Asks, “How Fast?”
Speed-sensitive damping asks the question, “how fast or slow the shock is moving?” Then, depending on the tune and technology, it applies damping force.
What do we mean by the “shock moving”? Technically speaking, this is how fast the shock shaft moves the main piston up or down inside the shock body. The easier to understand definition is “how fast the shock compresses or rebounds”.
The shock moves at a certain speed (low-speed or high-speed) in a certain direction (compression or rebound).
Now, in real life, low-speed vs. high-speed is really a spectrum with an infinite number of possible speeds between “slow-as-a-snail” and “faster-than-a-rabbit”. But, for our purposes right now, just think of speed-sensitive in terms of the two polarities: “low-speed” and “high-speed”.
Position-Sensitive Damping Asks, “Where?”
Position-sensitive damping asks the question, “where is the shock in its travel?” Then, depending on the tune and technology, it applies damping force.
What do we mean by “where the shock is”? Technically speaking, while the shock is moving, the main piston changing position inside the shock body. This moment it’s in one location, but in the next moment it’s in another location within the shock body. The easier to understand definition is “where the shock is in its travel”.
We describe the shock being in three zones throughout its travel, regardless of how fast it’s moving. Think of these zones as a range of positions through the shock travel:
1.) Top-Out Zone – Beginning of shock travel
2.) Ride Zone – Middle of shock travel
3.) Bottom-Out Zone – End of shock travel
Now, in real life, the actual position and number of these zones inside the shock are specific to the vehicle, tune, and application. For example, on the 2021 Ford F-150 Raptor actually has nine internal bypass circuits inside the shock that all work together to create a uniquely tuned feel for each of the three “zones” we use to describe the riding experience: “top-out”, “ride”, and “bottom-out”.
Examples of Controlling Speed-Sensitive Damping
You’re probably pretty familiar with low- and high-speed compression adjusters like X2, DSC and GRIP 2. Other adjusters like iQS, QS3, and GRIP adjust low-speed compression.
Shims on the main piston are another way to apply speed-sensitive damping. Shims are the precision-machined washer-shaped discs that bend as oil flows through the ports on the main piston.
Examples of Controlling Position-Sensitive Damping
External Bypass – uses external tubes welded to the shock body to allow oil to get around the main piston assembly. This offers maximum tunability and amount of circuits to refine the feel of the three zones.
Internal Bypass – uses an internal shock body with shimmed circuits to allow oil to flow around the main piston assembly. This offers maximum tunability and amount of circuits to refine the feel of the three zones.
Spiral Groove Bypass – uses grooves cut into the shock body that allow oil to flow around the main piston assembly. This offers a reasonable amount of tunability to refine the feel of the three zones.
Bottom-Out Control – uses a secondary piston on top of the main piston assembly. This offers a reasonable amount of tunability to refine the feel of the ride zone and the bottom-out zone.
Top-Out Control – uses a secondary piston on the bottom of the main piston assembly. This offers a reasonable amount of tunability to refine the feel of the ride zone and the top-out zone.
Other manufacturers offer other position-sensitive damping alternatives, but because Internal Bypass is patented by FOX, their non-external bypass position-sensitive shocks are unable to offer maximum tunability and amount of circuits to fully refine the feel of the three zones. Thus, their technologies are only able to moderately refine the feel of two zones at most.
Looking for more specifics on the felt benefits of position-sensitive damping and how these different types of position-sensitive technologies work? Stay tuned. #ridefox.com