I like to do all my own work on my bike, and with other forks and shocks I've had, I've been able to find the necessary service manuals and specialty tools to overhaul the systems myself at the end of the season. Now I have a Specialized Epic with front and rear Brain suspension. My local Specialized shop tells me that the only way to get the fork rebuilt is to have the shop send it to Specialized for their elite mechanics to service it.

Has anyone tried servicing these Brain systems on their on? Any resources to point to? Or is it just a hopeless endeavor and I'll forever be tied to swallowing my pride and paying for someone else to work on my bike?

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    If you decide to do it yourself, be sure to post the video on YouTube. I'm sure "DIY Brain Surgery" will get plenty of hits! Jan 8, 2015 at 23:04

3 Answers 3


I've serviced the brain on my 2006 sworks stumpy several times over the past few years, mostly because of the crummy turnaround times from spesh, and the fact that it never makes it through more than half a season before losing lockout etc. And the fact that I'm a mechanical engineer and stupidly tear into anything that breaks thinking I can handle it (half the time I can't).

I have to admit it took me about a year to get good at rebuilding it, the critical thing is you have to make sure there are absolutely NO air bubbles in the system when you refill it. Air bubbles getting into the hydraulic fluid seems to be what makes them fail.

There are a few threads out there that are helpful, and there's a rockshox monarch repair video that's similar enough to give you some good ideas. There are also schematics available on the net that are a huge help and also tell you what size o-rings etc you'll need (and make sure you replace them every time, at the least the standard ones which are easy to get from the internet or in my case my friendly neighbourhood hydraulic component shop), they're cheap and if you don't you have a good chance of failure. Note that some of them are Vitron (teflon impregnated), unless you have absolutely no choice replace vitron with vitron of the same color (durometer).

I had the schematics saved somewhere but haven't found them yet, that's how I ended up here, I'll try to remember to check back once I find them, and if anyone wants let me know and I'll pass them on.

I don't bother with nitrogen, I think the main reason they use it is the convenience of a high pressure cylinder of nitrogen versus using a hand pump or a high pressure compressor (you want to charge the brain side to 350-400psi). Some shocks do just use air. I put a schraeder valve on my brain and use a suspension pump to fill it, I can get about 350 psi into it. If you wanted nitrogen you could probably go to a motorcycle service shop and get them to charge the system for you.

To refill it I have used Fox fluid, but it's just rebranded motorcycle fork fluid marked up about five times as much. I've used Belray motorcycle fork fluid with success (It's available in a variety of weights so you can experiment a bit, I think I used 7 wt). I've also tried transmission fluid at someones suggestion, it works fine but smells terrible, I doubt I'll use it again. Whatever you use you need a lot because you need to have a bath of it you can fully emerge the whole system in while you reassemble to make sure you don't get bubbles, for me I need about a gallon minimum.

There's probably no reason to take apart the shim stack, but if you do be very careful and methodical, take your time and take LOTs of pictures. If you dont get it back together exactly the way it was it probably won't work, and I've only found shim stack diagrams for one or two models of brain.

Good luck!


If you want to do it the "professional" way, you would need some quite specialist equipment to fill the brain unit with oil and nitrogen properly.

However I have heard of people doing it on their own. The most complex tutorial I've seen is here: http://huckingkitty.com/forums/viewtopic.php?f=11&t=720 (note: I havent tried this and can't guarantee that this is correct). It does use nitrogen but at least the oil issue is solved simply.

Still there are some issues with this: for instance oil viscosity is not given. Also if we wanted to fill the Brain unit with air instead of nitrogen (yes, some people try this) the valve needs some modifications (I don't know precisely what modifications), and the air pressure is a matter of discussion. So the entire thing is quite complicated and I can't recommend doing it yourself unless you feel really confident in DIY stuff.

  • I don't know about this shock system, but I am skeptical that air versus pure nitrogen would make a difference in it.
    – Batman
    Nov 9, 2014 at 8:31
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    @Batman I agree, this is why some people decide to use it - in the end the air is mostly nitrogen. The argument of the other side is higher stability of properties of pure nitrogen under a range of temperatures and the fact that the air may contain some tiny amounts of water vapour, which may be a factor leading to corrosion inside the chamber over the years. Still I think it might be more of making the system more unique rather that improving pure mechanics of it.
    – Slovakov
    Nov 9, 2014 at 9:47

Not sure what year Specialized Brain you are talking about, but I have a 2005 epic. Both Fox and Specialized told me that they didn't have parts and couldn't service the unit!

I found the schematics on line, cross referenced all the seals and "proprietary" parts and have stripped the shock and brain down for rebuild. There is no mystery on the 2003 to 2006 Epics when it comes to filling the shock with oil and nitrogen. Replace the seals, change the oil - being careful to avoid letting air in - then replace the rubber fill pellet, pellet screw and fill Brain with nitrogen.

Fox will tell you this needs to be done by a tech, but all you need is a safety valve and needle, $20 to $50 on eBay, and someone with a nitrogen tank. The needle goes through the pellet which is self sealing. I don't about the newer ones but that's it to fixing the older ones. Quick hint, have of the parts in the Brains are used in other Fox products, like ATV, truck and other bike shocks.

PS - I have seen people converting to air. Not sure why anyone would bother when the nitrogen pellets are only $1.00, the special needle and valve $20.00 and $4.00 for nitrogen at your local tire place.

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