Above: the Charger 3 headvalve cutaway, showing the High Speed Compression (HSC) and Low Speed Compression (LSC) adjusters.
In suspension, dampers are paired with springs to control the speed at which the spring absorbs and releases energy, using a system of valves that allow the oil to flow freely (the Open position), or restricts the flow of oil (the Closed position). When we say to open up your suspension (or reduce damping), that means there is less restriction of oil, and the suspension will compress more freely. When we say to close your suspension (or add damping), that means the oil flow is restricted and will take more force or time to compress. This theory applies to both High Speed Compression (HSC)—which controls how the fork feels in high-speed, quick impacts, and Low Speed Compression (LSC)—which controls how the fork feels in gradual compression events like corners, weight shifts, and transitions. It also applies to Rebound—but that’s a conversation for another time.
In traditional dampers, HSC and LSC are a part of the same flow network—adjusting one also adjusts the other. For example, you adjust your HSC because the fork feels rough or jarring on this trail (but felt great on the last one), and that also adjusts the LSC, which then can make the fork feel unsupported or floppy. We call this "cross-talk"—when one adjustment "talks" over the other.
Lynch explains, "Essentially, when you adjust your High Speed Compression, you are adjusting preload on a spring that's pushing on a shim stack, offering resistance in the oil path. When you open the High Speed Compression adjuster, the shim stack is free to lift, allowing oil to flow more easily. Unfortunately, that shim stack is also what's creating your back pressure to make that Low Speed Compression adjuster valve work. So, you end up with this unintended and unwanted link. With no High Speed Compression tension on the spring, there's no pressure on the shim stack, making your Low Speed valve ineffective."
So, How Does Charger 3 Work?
Above: Demonstrating oil flow with the LSC circuit closed, forcing the oil to flow through the LSC hard path. Notice the oil flow through the hard path (the outside path within the red sealhead) is pressurized, creating more damping.
Now that we've explained how it works, let's take a look at a compression damping study measuring the effectiveness of HSC and LSC adjusters in other dampers versus Charger 3. Figure 1 below is a sample damping curve with Force (amount of damping from low to high Force) on the Y-axis and Velocity (the speed at which the damper moves from low to high speed) along the X-axis. As you increase Velocity, you also increase Force and vice versa.
To show exactly how effective HSC and LSC adjusters are, we compared the Other Damper’s range of compression adjustability (Figure 2) to Charger 3 (Figure 3). Both Figure 2 and Figure 3 show similar HSC and LSC damping curves when both are Open (green) and Closed (red). Where they differ is those dotted lines in the middle: blue representing the LSC closed and HSC open, and yellow representing LSC open and HSC closed. We’ll take a dive into the relationships between the lines and what that means for adjustability.
With Other Dampers (Figure 2), compare the solid green Open/Open line with the dashed yellow line representing LSC open and HSC closed. With the LSC open, it follows the solid green line closely while in the low velocity range. Then as Velocity increases, Force also goes up. This is what you’d expect to see with HSC closed and LSC open. It gets confusing when comparing the blue dashed line (showing LSC closed and HSC open) and the solid red Closed/Closed line—both these lines have the same LSC position: Closed. The force of the LSC should go up when the adjuster is closed to match the solid red line, but instead, the force goes way down, almost to the solid green Open/Open line. This relationship demonstrates the link between HSC and LSC that we covered earlier in this article; adjusting HSC removes the tension from the shim stack and renders the LSC valve mostly ineffective. Overall, this chart shows that the LSC is highly dependent on the HSC setting, and therefore the adjustments are not independent.