Adjustable Shock Assembly Fox Factory

In this article, we’ll be discussing an Adjustable Shock Assembly Fox Factory, US publication 20220403909. The publication date is Dec 22nd, 2022 and the filing date is June 15th, 2022. This is not granted at the moment.

Brief Summary (tl;dr)

Fox are working on another iteration of their Live Valve system. In this document, they show a rear shock with an active valve system, a passive compression valve, and a passive blowoff stack. The compression valve manually controls fluid flow to either the active valve or the blowoff stack. The rider can turn a knob to adjust the amount of blowoff pressure the blowoff stack relies on, which allows fluid flow to move to the piggy back reservoir using another flow path other than the active valve flow path.


While they aren’t the first to attempt an active system, they’re arguably at the forefront right now. I recently wrote an interesting article [LINK} about, what I’m assuming to be, a more user-friendly and less expensive version of their Live Valve. The product in this document may or may not be related to that. I’m going to take a wild guess and say this is a next iteration, but that’s pure speculation.

By now, most of us are aware of the Fox’s Live Valve system. Live Valve is an active suspension system, taking inputs from sensors around the bike to automatically adjust shock damping settings without direct rider input. As a result, the damper has an infinite amount of automatically determined settings.

I was watching Hard Line last year, and Reese Wilson made an interesting comment that got me thinking. Without directly quoting, he explained the difficulty in setting up a bike for a run like Hard Line because the bike would need to be set up for things like high-speed berms, massive drops, and smaller drops toward the end. When you watch the end-run drops, you can see how violent the impact is with the ground, and subsequently violent on the rider. This is, primarily, due to the bike’s setup for the huge impacts – likely more closed fluid paths (speculation). You take those same fluid paths to lesser energy-intensive drops, that energy isn’t absorbed by suspension, but rather by a rider.

I say this because this is exactly what an active suspension system could alleviate. Imagine a suspension that can be set up correctly for a massive drop, then the little rocks, then the berms. This would be on-the-fly and without direct human intervention. Each instance is compartmentalized and dictated individually.

And I’m sure you’re wondering “How the funk will the bike know?”. Based on some other Fox documents, and some other research around the interwebs, I think they’ll use jolt (jerk). Jolt is the first derivative of acceleration, which allows for extremely immediate data acquisition due to the super high rate of change of values. For my options peeps, this is a gamma equivalency.


Fox do a great job with their documents. They take the time to define fully active, semi-active, and passive system. Why bother paraphrasing when they explain these terms so well?

Fully active – In a conventional “pure active suspension”, a motive source such as, for example, an actuator, is used to move (e.g. raise or lower) a wheel with respect to the vehicle.

So, fully active would be the active F1 cars, which placed the car at a specified attitude given speed, steering angle, etc. for peak aero gains. Side note, is sounds like they’re looking to bring active aero back to F1 in 2026. That’ll be interesting.

Semi-Active (adaptive) – no motive force/actuator is employed to adjust move ( e.g. raise or lower) a wheel with respect to the vehicle. Rather… the characteristics of the suspension ( e.g. the firmness of the suspension) are altered during typical use to accommodate conditions of the terrain and/or the vehicle.

So, in a semi-active system, there’s a separation between the actuation and movement of the component. In other words, the system allows the suspension to move a certain way, rather than directly moving the suspension at a desired rate and to a desired location. This is what Fox are using.

Passive – …characteristics of the suspension are not changeable during typical use, and no motive force/actuator is employed to adjust move (e.g. raise or lower) a wheel with respect to the vehicle.

Passive systems are the traditional systems we all enjoy today. There’s one input action and one output action, based on how your suspension is set up. There’s no decision-making going on inside your bike. The only decision-making is your bad decisions.

The images below are, from what I can find, the only public images of this new system, full credit to Pinkbike. There might be more out there somewhere, but I can’t find them. If you’ve got some, shoot ‘em my way.

Hopefully this report gives you some more info on what we can expect in the future.


At this point, I think we’re all aware of why Fox have been developing Live Valve. From a super-high level, they simply want to automatically adjust the suspension settings based on terrain. Really, like with any active system, they want to provide a seamless suspension experience, while maintaining grip and efficiency.

…depending upon the terrain being traversed, it can be valuable to be able to change the amount of shock absorption provided by the shock assembly for personal comfort, vehicle performance, and the like.

This particular document relates to an active system with a manual compression valve and blowoff stack. So, why do they have both a compression valve and an active valve? That seems redundant. This is why:

…compression adjuster 210 is used to achieve a desired compression setting while the adjustable active valve assembly 205 is used to achieve a further compression setting where the two components working together achieve an “additive” damping characteristic that includes a level of granularity that is not found in conventional shock absorbers.

As far as the blowoff stack goes, they don’t have explicit reasoning, but it’d take a guess it’s for suspension safety (not grenading your shock) and improving fine adjustments for different types of bikes (enduro or cross country, for example).  


FIG. 1 shows a rough overview of the bike showing a whole bunch of stuff. First, this bike needs some sensors 35 that are located around the bike, which:

…read bump input at the wheel and send the obtained sensor data to the suspension controller 39… [to] adjust the suspension for maximum efficiency and control. … data [includes] angle, orientation, velocity, acceleration, RPM, operating temperature, and the like, can be obtained.

We’ve also got a switch 93, mobile device 95, a controller 39, a shock 38, and so on. The switch would be some buttons on the handlebar to select different modes and the mobile device is your phone, just like the current Live Valve system. I’d assume these would perform similar functions.

In one embodiment, switch 93 is a positional switch used in conjunction with the active suspension system 75… that can cycle through a number of different modes (similar to a gear shift), or the like.

Continuing, FIG. 2 shows this sexy new shock. The first thing I’m seeing are the knobs. We’ve got three of them; rebound 215, compression knob within 210, and firm mode adjuster knob within 205. Rebound and compression are obvious and I’m not going to talk about those, but the firm mode adjuster knob is the new dangle. We’ll get into that later.

Again, we’ve got our normal components like the eyelets, air sleeve, reservoir, and all that shit. From the outside, we can really only see two things that appear different; the power source 65 and controller 39.

If we take a look at FIG. 1B above, they’ve got the controller and shock separated for schematic purposes. In reality, they’re likely going to be one assembly. Again, the controller is the brain, which takes the sensor information from the sensors, does dank-ass math, and tells the suspension to do things based on the sensed information.

We’ve got to power this thing somehow, right? Fox have quite a few options, so we can do what the internet allows us to do, and once again anonymously speculate on what we’ll see in the wild! They say it can be a rechargeable battery, which can be recharged with a wire or wirelessly. To that point, how the hell does wireless charging work? I feel like ICP with their magnets; ‘…fuckin’ wireless charging, how does it work…’. It’s crazy stuff.

…the power source is a rechargeable battery… the power source can be recharged wired or wirelessly… E.g., using an inductive charger… [systems can include] the wireless power consortium (WPC) Qi standard, the AirFuel Alliance (e.g., Duracell Powermat, PowerKiss, etc.), WiTricity, and the like.

This part is interesting. Fox also say the power source can be energy harvesting, which converts the vibration of the bike to energy. I imagine this works similarly to those never-ending flashlights that you’d put in a bunker. Thought: does energy harvesting reduce as you improve your suspension setup? Hmm.

…the power source is an energy harvesting switch that does not require a battery or other powered connection… is capable of operating for an indefinite amount of time without requiring any type of recharge, battery change, etc… such as ZF electronics AFIG-0007…

FIG. 3 shows some insidy-parts. We’ve got a chamber 121 (fluid), air sleeve 123, piston shaft 130, and piston 131. When the air sleeve moves relative to the fluid chamber (i.e., shock compression), fluid passes through the piston, through the piston shaft, through valves, and into the piggy-back reservoir. Bada bing bada boom.

For you old heads, you might notice the lack of a boost valve. RC did a good report on Fox’s boost valve here, or this by Vital. They’re doing this because:

…by not requiring a boost valve arrangement, the shock assembly 38 is a smaller package with fewer parts that a shock assembly with a boost valve arrangement, which will reduce manufacture costs and speed. Moreover, shock assembly 38 as described herein will reduce clunking and provide a faster response time compared to many other shock designs.

There is something here that caught my attention: the component 172. They’re calling this the ‘bearing housing’. They have zero information on this thing and only mention it once, but wut in tarnation is a bearing housing? Are they putting bearings in this thing now? Because that’s typically a seal. Or do they just mean the seal ‘bears’ against another surface? We should find out eventually.


FIG. 4a shows the important insidy parts. This time, we’re looking inside the piggy-back. We’ve got the compression adjuster 210 and the active valve 205.

The knob 512 of the compression adjuster controls the fluid flow in compression valve 511. We can see the fluid flow path through the compression valve, which then passes to the active valve 205. I don’t think there’s anything groundbreaking going on here.

The active valve assembly 205 includes the active valve and the blowoff stack. The active valve uses a needle that sits against a valve seat to control fluid flow, where the needle is moved via a solenoid (that’s the active part). So, the computer will activate the solenoid, which moves the needle to certain positions to allow a certain fluid flow through the valve.

The unfortunate part here is that I cannot explicitly tell you where the solenoid, valve, and seat are because Fox don’t note them. That being said, I think we can take a guess, shown above. I know you’re probably wondering if this is binary (open/locked = downhill/climb). While I can’t say for certain, it’s likely it could be infinitely adjustable.

In one embodiment, the active valve 521 is infinitely adjustable.

It’s important to note the two parallel flow paths (green box) inside the active valve assembly. The parallel flow paths flow in opposite directions (left/right), one to the active valve 521 or one to the blowoff stack 525. I know it shows two going to the blowoff stack, but it’s one flow.

Blowoff Stack

Alright, what is this blowoff stack? Fox don’t explicitly say “The blowoff stack does XXX…” so I’ve got to make some assumptions.

EXT (here) defines the blowoff system as, effectively, a release of fluid flow to another channel when the shock encounters a velocity outside the normal operating range of the shock. For example, if a shock is designed to operate between 0 and 50mm/s, this can be considered 0-100% operational speeds.

Now, let’s say you fuck up and smash a rock going way too fast, and the shock now moves at 80mm/s. The blowoff stack up tuned to release fluid flow through a separate channel, to allow the shock to properly operate, and likely reduce internal damage. Additionally, a blowoff system can also be used for actual performance, rather than safety.

So, the knob 527 controls the blowoff pressure of the blowoff stack. As you turn it, the pressure of the stack is adjusted, thus the blowoff pressure is adjusted.

If you read one paragraph in this wall of text, it’s this one:

Ultimately, we can think of this shock as an either/or situation (which is where the two parallel flow paths come into play). Either the fluid goes through the active valve or the blowoff stack. When the fluid pressure/velocity is within a determined operating range (0-100% for example), the blowoff stays closed, and the active valve controls the fluid to the rezzy. When the fluid pressure/velocity is too high, the blowoff allows flow to pass through to the rezzy and not through the active valve. So, I’m thinking of this as passive at >100% pressure/velocity and active at <100% fluid pressure/velocity.

Again, the top range of fluid pressure/velocity is adjustable with this knob.

…the amount of damping and on-the-fly damping adjustability available to shock assembly 38 is no longer dependent upon either adjustable active valve assembly 205, compression adjuster 210, or any other single component. Instead, the amount of damping and on-the-fly damping adjustability available to shock assembly 38 is enhanced by the combined, individually tunable characteristics, of adjustable active valve assembly 205 and/or compression adjuster 210.

FIG. 4b shows a cutaway of the reservoir and the internal floating piston IFP. They’re just showing the fluid flow from the active valve to the rezzy.

Setup and Tuning

Fox has also included an ‘Initial Set Up/Tuning’ section as well. Here’s how it’ll work.

  1. Turn off the controller, which opens the active valve and puts the valve in an open state
  2. Rider then goes downhill and adjust the compression 511/512 until they’re satisfied. The compression is established and doesn’t need to be touched again (for the most part).
  3. The controller is then turned back on, which closes the active valve and puts the active valve in a closed mode.
  4. The rider then finds an uphill track and does some climbing.
  5. The rider then adjusts the blowoff of the active valve with knob 527, which adjusts the blowoff pressure, until they’re satisfied with the climbing ability.
  6. Finished

These settings are now the baseline settings for the bike and rider. Alternatively:

…cross country racers might crank the blowoff pressure of firm mode blowoff stack 525 close to full (or nearly full) lockout while an enduro or trail rider might want a bit of compliance so they would set the blowoff pressure of firm mode blowoff stack 525 to less than full (or nearly full) lockout.


This system has a lot going on, with both manual/passive systems and an active system. I would think this would be very difficult to tune, but I’m confident the Fox folks aren’t idiots and will have this sussed out. I’m just really curious as to how the active system will react when the blowoff is activated. Is there a reactive sensor in the active valve that says “blowoff is open”, and does this change what the active valve does? Does it even matter?

Or, does the active valve know the blowoff pressure, and is the valve then mapped based on the blowoff pressure?

From what I can tell, the goal is in granularity, and it seems like they’re on the right path. Whether it works is a whole different story. I look forward to seeing the ‘tech’ reviews.

And I’m beating a dead horse here, but I’m still yet to be a fan of these systems explicitly in race bikes. Who gives a dick if some rich dude on their E-bike flies past you on the trails with their new Live Valve; live and let live. That being said, the use of any automatically adjustable system in a race bike just don’t sit right. But, I’m enough of a pacifist in this situation to not push the issue either way. I’m more interested in seeing how the public moves this concept forward.

One can argue that an active system is simply an extension of an engineer’s brain, which then provides some level of manual logic to the system. But, we’ve got to establish a line. Where’s the line when implementing a secondary thought process on a bike? In my mind, it’s the use of an active processor. Once a processor like this is used, we’ve stepped into a new realm.

Yes, there’s a processor in a SRAM AXS shifter and the like, but it’s not active. It’s got one input and one output. Press button -> shift. But that’s likely going to change in the future, too – automatic shifting.

Lastly, is this cool? Do I want to have a beer or sit around a campfire all weekend with this person?

No, it’s not cool. It’s extremely impressive, well thought out, likely beautifully made, but it’ll never be cool. I like to think Jeremy, James, and Richard would agree.

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