2018 Specialized BRAIN shock cutaway diagram and tech details

To make the all-new 2018 Specialized Epic FSR as efficient and capable as possible, they had to rethink their BRAIN suspension platform. Over the past 15 years, it’s seen a little innovation, but it still relied on a brass mass to hold the ports mostly closed until the rear wheel hit something hard enough to move the axle faster enough such that a spring couldn’t hold the mass against the ports, and it opened flow.

The new version switched it around a little by leaving low speed ports open so the shock is sensitive to small inputs without succumbing to pedal bob. The Horst Link design is, after all, a very active suspension platform that benefits from something like the BRAIN when pedaling efficiency is more important than wide open bump absorption. So, the brass mass inertia system is still there, it just leaves a little gap at the top for small bump oil flow to pass by.

In the image above, the new 2018 BRAIN system is shown on top of last year’s model. Note how the hose connecting the air canister with the BRAIN canister runs directly through the yoke. Another external difference is the reservoir now sits separately atop the damping circuit. Let’s take a look inside…

2018 Specialized BRAIN shock cutaway diagram and tech details

Here’s what you’re looking at, click to enlarge image:

A: Brass Mass (BM)
B: Biasing spring that holds BM in place
C: Spike Valve
D: BRAIN Fade Knob
E: Emergency blowoff valve
F: One-way check valve to control oil flow direction
G: IFP Bladder

And here’s what all that stuff does: The brass mass (A) wants to stay put (an object at rest tends to stay at rest). In the Firm position, ALL of the oil is running through a damping circuit. As you open it up, oil starts to bypass the BRAIN system more and more, up to the point where you’re barely able to feel any platform. In the prior BRAIN shocks, once you moved it into any open setting, the oil essentially bypassed all of the damping circuits, effectively taking away a lot of the shock’s performance even if you only wanted to “soften the nose” off the platform. Now, you get actual, discernible platform adjustments without giving up normal low- and high-speed compression damping.

The BRAIN knob (D) turns a shaft running through the center of the valve body, which turns a plate with a large kidney shaped hole in it over smaller ports. In Closed (Firm) mode, the plate is completely covering all ports. With each click (four levels of Open), it uncovers one small hole per click.

They’ve also done away with the traditional IFP in favor of a bladder (G). Normally an IFP (Internal Floating Piston) is just that, a piston inside the shock that separates a pressurized nitrogen chamber from the oil. It keeps the oil flowing properly and doesn’t allow any room for air bubbles (aka cavitation) to form since there’s always pressure on the oil. The downside is that the seals on the piston must be tight because the nitrogen chamber can be up to 300psi. A bladder doesn’t suffer from any of that stiction, and it produces less heat because it’s not sliding against the sides of the canister. Specialized puts 180psi of nitrogen gas inside the bladder to maintain pressure on the system to prevent cavitation.

The Spike Valve (C) is a regressive valving that produces a flat compression curve, which means it maintains control and movement deeper into its travel. It works by controlling oil flow more carefully up to a specific flow speed, after which it dumps open to take a big hit. Inside the Spike Valve is the entire low speed compression circuit. There are flow ports leading to a shim stack, which gives them the low speed control they want. Once flow rate is too fast to move through those ports and/or the shims are bending too much and starting to ramp up their resistance (essentially creating hydraulic lock because the fluid is moving too fast for the ports), then the entire low speed circuit simply slides up and out of the way to let more oil flow around it. What that means for the rider is that it’ll stay plush and smooth even through successive big hits instead of jacking up because the spring rate isn’t ramping up too steep at the end of the stroke.

2018 Specialized BRAIN shock cutaway diagram and tech details

Here’s the oil flow path, dotted lines indicate oil flowing inside/through a circuit (click to enlarge). Oil enters the damping circuit along the red line. The green line shows where oil flows through a central port toward the brass mass. More oil is able to flow past it the more you open up the BRAIN platform using the blue knob. A big hit causes the BM to slide down and let all the oil flow past it, then the spring pushes it back into place to close off the ports. Oil then flows around the center assembly (orange) and into the Spike Valve and low speed circuits, then flows into the reservoir (pink) before returning through the entry port.

2018 Specialized BRAIN shock pulls apart for easy service

Another nice update is the improved serviceability. Because the oil and IFP are contained inside the BRAIN unit, the air canister can be easily removed with common shop tools and cleaned, lubed and inspected, then right back on the bike in about 10 minutes.

The new BRAIN shock retains their Auto-Sag feature, making setup quick and easy, taking all the guesswork out of your initial position. My test rides left it where it ended up and it worked great on a well planned XC course. Stay tuned for our first ride impressions, actual weights and full retail pricing and specs over the next few days.



  1. Is the spike valve really regressive? I’d expect it to be highly digressive. Regressive basically means that it takes less force to keep the valve open as it does to open it in the first place.
    I’d like to see a shaft speed/force graph

  2. I’m surprised they didnt go full electric for the suspension control yet, with an accelerometer instead of a mechanical/gravity activated valve

    • I’m really surprised too. Automotive has been using this tech for over 15 yrs, Including MR fluid by GM. Use a microprocessor and 3 or 4 sensors (to which the size has been shrinking). Even an accelerometer on the fork can tell whats going to happen to the rear wheel.

  3. I’m sooo sure moving to a bladder system will make Brains serviceable…pfft. The air can was always serviceable. They get shipped to them(Specialized) BY DEALERS for damper service anyways. Looks like they’re moving to a Rockshox manufactured product, which, these days, means a screw off warranty.

  4. me too, this is absolutely the future.

    I suspect part of it is that Specialized doesn’t have a lot of in-house electronics engineering expertise. I would hope they are staffing up in this area.

  5. This is all race car spec stuff using inertia valving (probably a Rich Thorwaldsen design).
    Top of the knowledge curve stuff. I wish somebody else was using this on Trail/AM bikes.

    • This is not race care spec stuff. This is marketing garbage. No offroad race vehicle anywhere in any class of any series uses a design as stupid as this. No engineer or physicist would think of this as a reasonable idea. Specialized simply puts nonsensical items on to sell bicycles. I have one. I threw it away after about 5 rides. It’s a terrible idea that should have died during the brainstorm session that came up with it. It doesn’t work. Physics dictates that it CANT work the way they want it to. And it’s expensive.

      • I’m seriously thinking about this system and my conclusions are not that far from yours. In a few days I get a new Specialized full suspensions (they made an offer a couldn’t refuse “”the God Father’s” 🙂 So I gonna see how it works on the “real world”.
        In my pocket I alreay have a plan to take it off 🙂

  6. “Over the past 15 years, it’s seen a little innovation” Horst time is so over and you’ve made the $ from the patent! Time to move on… VVP and many other designtreatments do not require any “brain”…. just an opinion, we all have them;-)

          • I had to look at a photo of a known VPP (Tallboy) and the BMC. I see what you mean with regards to the rotational direction of the two links. Thanks.

      • I think you would have to go all the way back to Niki Gudex on an Intense Spider in the mid 2000s for either of the VPP using brands to actually have a World Cup XC racer. She won Aussie nationals, but no World Cups. Plenty of short link designs (similar to DW link) being raced and won by BMC and Giant though.

  7. When I want a hard tail, I ride my SS, when I want suspension I ride FS. Better solution. AND AN EXCUSE TO HAVE MORE BIKES…..WHICH IS THE GOAL RIGT….

  8. This question goes out to Specialized directly: WILL NON SPECIALIZED DEALERS OR END USERS BE ABLE TO SERVICE THIS PRODUCT? You’re hurting your customers if you don’t allow it.

    • This isn’t a coil spring shock on those supermarket bikes you see car wash employees riding. This is a precision product.

      Do this: Go to a Porsche Cayman and access the engine. You can’t. It’s sealed up, because they don’t want armchair mechanics working on them. Otherwise, you should’ve bought a Camry.

      In fact, they raised the service interval on this shock to 200 hours, so there’s that. I never understood why people don’t mind precision in their cars–and will pay to have it properly serviced–but still bikes are stuck in the 1900s.

      • This is nowhere near the complexity of an integrated and mature automotive product. I’m not an armchair mechanic–I’ve performed overhauls on most major brands of shocks and forks, so this isn’t any different. They’ve simply relocated some oil volume, and added additional valving. They won’t release the info to IBDs, which is BS if their local dealers don’t have the capability but we do.

  9. Much ado about the straight route through the yoke to avoid a bend, now the very same bend is moved at the Brain unit. The picture above is unforgiving!, so much for a cleaner looking bike (which is always good anyway, but don’t justify it with technical arguments, pleeeeeze)

  10. People are a little ridiculous. They have no idea, all the mechanical technologies that await them outside the ‘closeted world’ of bicycle corporations. There are all kinds of neat technology that NOBODY will ever throw on a bike because there’s just NOT ENOUGH MONEY TO BE MADE.

    I wish I could tell you of all the cool designs and ideas I have, as a mechanical engineer, that won’t see the light of day. But, you can find them in F1, LeMans, and Military applications, no problem.

    It is sad, I know, it depresses me, but what can I say, there’s really not much money to be made, the bicycle market is very small really when compared to a military contract.

  11. This looks to be the right place with skilled people. So, I try: anyone who can suggest a way to get the service kit for the new Micro Brain 2018-2019 rear shock absorber?

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