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Udi's guide to bleeding your DHX Air

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
Not sure how many people this will interest, but I know there's nothing out there on the topic (and there have been a couple questions about it) so hopefully this will be useful at some stage.

Most people will know how to service the air sleeve on fox air shocks, as they provide detailed instructions on how to do this. It's very simple and worth doing to keep the air spring running smoothly, and prevent seal issues that cause stuck-down shocks.

But bleeding these things seemed a bit of a black art, you couldn't really just dump it in an oil bath like a conventional shock, and there were many telltale signs that this wasn't the way it was done at factory. My original ideas are in this post, and that's pretty much the method this guide follows. I'm lazy so this assumes you can bleed a standard shock, set IFP depths, etc. :)

1a. Relieve both pressure valves
1b. Remove airsleeve (refer fox instructions)
1c. Remove resovoir endcap (24mm socket)


2a. Remove plastic plug from bleed port screw (takes 4mm key)
2b. The above is a pain, but you only have to do it once
2c. Be really careful not to scratch the shaft in the process


3a. Obtain boxxer rebound footbolt (hollow)
3b. Wrap threads in teflon tape to assist sealing
3c. Thread bolt into bleed port, 1 to 1.5 turns only


4a. Get a big syringe, attach thick tubing, enough to fit over bolt
4b. Ziptie tubing to syringe and bolt, tightly
4c. Fill with oil of choice
4d. I used a 50/50 mix of Silkolene Pro RSF 2.5 and 5wt
4e. Refer to this post for bleeding method.
4f. Keep syringe vertical at all times (not shown) to prevent air entry


5a. Set IFP depth, 35mm is a good starting point
5b. Close everything back up
5c. Be sure not to let air enter anywhere


6a. Grease all air seals
6b. Reinstall air sleeve/s, leave a gap to pour oil in
6c. Add 10-15ml of lubrication oil into air chamber
6d. Fully close air sleeve, thread shut.
6e. Repressurise everything
6f. Double check boost pressure, it will change after filling main chamber.

7a. Reinstall shock and ride!
7b. If it's too loud, you let air in...
 

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
Also as a side note, some of you might remember how I found a blown glide ring last time, well to save me the fox service/rebuild I crafted my own out of an "iglidur" brand glide bushing. Seems to be working sweet so far. :)

Old (piece missing):


New (installed):
 
Last edited:

Dirtbike

Monkey
Mar 21, 2005
593
2
eastbay
Do you know of a procedure for the Float shocks? There is a special fitting to pressurize the IFP, no? I might be able to get ahold of one, and fix an old shock.
 

JohnnyC

Monkey
Feb 10, 2006
399
1
Rotorua, New Zealand
Nice one Udi that looks like a tidy way to bleed it, I like how the Boxxer footnut makes a good fitting. I'll be referring to this when I come to doing one, cheers!

As for orientation of the shock mentioned in that other post, my theory was that it makes it easier to service the air can as that needs to be done more regularly than a damper service.
 

S.K.C.

Turbo Monkey
Feb 28, 2005
4,096
25
Pa. / North Jersey
Udi - good stuff!

I know of a local guy from Diablo Freeride Park that almost killed himself disassembling his DHX with the whole "stuck-down" position thing...

:biggrin:
 

Dirtbike

Monkey
Mar 21, 2005
593
2
eastbay
Been huckin? :p Its a bottom out bumper. To replace it you would have to disassemble the shock, and remove the piston from the shaft to slide a new one on.

Udi- any ideas on the float?
 

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
Dirtbike - If I had a float, I could probably tell you... unfortunately my guess is as good as yours, there must be a special way/fitting to pressurise the area behind the IFP. You'll have a better idea than me with the shock in front of you - once you know what sort of thread/area you have to work with, you can make your own fitting or find something that'll fit. Sorry I can't be more help.

Netwelle - What dirtbike said. You'll have to bleed the shock afterwards, it might take 2-3 goes to get it air free (since the damper will be empty after fixing your problem)

JohnnyC - Cheers... not sure what theory you're talking about though, I didn't see another post from you.

SKC - Yeah the fox guide has a few warnings on that, I've had no such issues though - maybe because mine is 07 (I think they updated seals after 06 to fix the issue) but keeping everything lubed well would be a good way to prevent it.
 

JohnnyC

Monkey
Feb 10, 2006
399
1
Rotorua, New Zealand
JohnnyC - Cheers... not sure what theory you're talking about though, I didn't see another post from you.

In the other thread you linked to someone was wondering why the DHX had the resovoir at the same end as the air can, and thats what I was thinking. Make its easier to get the air can off
 

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
Johnny - Oh yeah for sure, never really thought about that, but it is pretty convenient how easy it is to get the can off. I'm not sure that would have been the only reason, but it's definitely a good one.

Netwelle - It should be fine to leave it as it is, honestly such a piddly o-ring isn't going to do much for bottom out protection anyway - probably just keeps it quiet. You must have been bottoming out hard to break the thing though (mine was still looking nice and intact, and I do use full travel pretty much every run)... so my advice would be run your bottom out adjuster in a little more if you can, or add 5-10ml of oil to the air chamber to increase progressiveness that way.
 

dowst

Chimp
May 9, 2008
8
0
Awesome guide Udi! Really, this website seems to have the largest amount of info on DHX air's than any other spot on the internet.

Netwelle, just opened up my DHX Air and found the same thing as you, the little o-ring had torn and was just floating around in there! I intend on taking it all apart and possibly fabricating/modifying a new bottom-out bumper out of one of Fox's coil bottom out bumpers. What do you guys think about this idea?

A few questions, I don't have the Boxxer foot-nut. Is this mandatory for bleeding the DHX air or is there a substitute? Also, my DHX is a 2.00" stroke, about what depth should the IFP be set? Is there any way to completely rid my shock of the Pro-pedal platform damping?

Again, awesome resource (props to UDI) and look forward from hearing from you guys!

Thanks--
 

jgixer

Chimp
Sep 5, 2008
2
0
Great guide, Udi.

A concern:
I had a small ball bearing(.095") roll onto my workbench. It was a surprise. I can't find a reference to this ball bearing anywhere. I first thought it was from the rebound adjustment detent. It is not, unless there are two bearings associated with the grub screw and spring assembly. From the cut away photos I can't seem to find its original location. :think:

Also a question:
Anyone know why the reservoir boost valve (schrader, I'm guessing) is not available on Specialized Enduros?

Thanks for the guide and any help you can give regarding the bearing.
 

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
There are no balls used in the damper, so it must be from an adjuster. The adjusters that have detents are propedal and rebound. The rebound ball is under the grub screw on the reservoir arm, and the propedal balls (there are 2) are under the propedal adjuster. If you didn't remove the grub screw or the propedal adjuster, the ball is not from the shock.

The enduro has a custom shock from fox that does not have the schrader valve because specialized are idiots and asked for it this way. It makes it impossible to bleed at home unless you: a) have the gear to nitrogen fill it like they do at factory, b) modify your own schrader valve onto it, or c) swap over an endcap from any other dhx3/4/5 air or coil that has the valve.

Hope that helps.
 

jgixer

Chimp
Sep 5, 2008
2
0
Thanks. It does help! I wanted to give someone with experience a chance to stop me before adding a schrader to the cap.

As for the ball bearing... I didn't disassemble the propedal adjustment, but I'll check it anyway. I'm beginning to think the ball was left over from a repair on my pool vacuum. I really gotta start cleaning up between jobs.

Thanks again.
 

gizmo

Chimp
Nov 9, 2003
2
0
i Know its and old post an everything, but y think the question is valid.
HOW ABOUT US GUYS THAT HAVE THE "DHX 4.5 air" thats on 06-07 specialized enduros, without the air valve in the reservoir?????...
UDI do you think its is possible to self service that shock???
How do you guys think i can put the requiered amount of air in the reservoir to keep the IFP running ok? Remember that it came pre-set at 125 psi from the factory!

Has anyone here putted and air valve back on it??
Hope you guys can help me, im from CHile, and the nearest fox autorized dealer and service its like in South cali or something lol.
Cheers
 
For the Specialized DHX "4.5" you need a special nitrogen tool to charge the reservoir

Your best bet is to try to buy a normal reservoir cap with the schrader valve and retro fit it to the shock. This will make your shock a stock DHX5

With all the DHX5s in the market you should be able to find a scrap one.

Best of luck.

JT