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X-Post Fox RP3 - Unserviceable?!?!?!

91K views 139 replies 35 participants last post by  fansaldi 
#1 ·
So, I've been around motorsports, snowmobiles, dirtbikes and the like over the years. I've also been biking over half of my life here on earth, so I know a few things about servicing Fox shocks. This brings me to my current rant.....

I have an older RP3 shock that needs new damper oil and a nitro recharge. I've done the air sleeve (many times) and I DO NOT NEED any custom valving (aka Push). Apparently NO ONE, I mean NO ONE other than Fox and Push can recharge the nitro?!?!?!

When I used to re-valve my snowmobile shocks we had a huge bottle of nitro in the shop. A matter a 30min to re-valve, re-charge and I was back riding my snowmobile seeing what effect the changes I made had to the suspension. It was no biggie. Anyone could do it. Seriously, it isn't hard to recharge the nitro with the needle tool.

This brings me to my current dilema..... I don't want to spend $100+ dollars just to rebuild the shock to normal condition. I just want to refill the damper oil and recharge the IFP chamber. Hell, I'd be just fine using air instead of nitro, but that doesn't seem possible without the tool. (which NO ONE has, except Fox and Push)
What is everyone doing with this situation? I talked to Fox and they want $120 for a full rebuild! I'd go the Push route for a little more than that, but I'm fine with the Comp and Rebound functions.

Has anyone found a cycle/sled shop that can recharge the nitro side of things? I'm worried the needle guage is slightly larger than what the MTB shocks need.
I've found some good info online and even found a massive zip file of Fox documents with exploded views, specs, and the like for my shock. IFP depth and the like. The file even has a service update in which Fox is telling dealers that the Nitro side of my RP3 is now getting pressurized to 400psi instead of the 'normal' 300 psi. I don't even have the means to pressurize something to 400psi......

I'm really frustrated with Fox right now. Great product until it needs servicing and then I'm supposed to pay almost half of the cost of a new shock, just to rebuild my old one!?!?
I am more than competent and confident to do this myself, but how?

Any help on the matter is appreciated and I know I'm not the first to ***** about Fox's proprietary damper. Feels like a Monopoly with Fox and Push being the ONLY ones that can work on these.

/Rant, Just needed to get that off my chest!

Please tell me I don't have just 2 options!
 
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#60 ·
Bumping old thread.
Was working on my float r, trying to rig up a needle system for using just air.
Was in my garage and a fitting caught my eye. On the fuel rail of 2.3 and 5.0 efi Ford's there is a removable fitting with a Schrader valve on it for checking and releasing fuel pressure. It has the correct size 5/16 24 to screw into the nitrogen port. :thumbsup:
 

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#81 ·
Thanks for the info PMK. I agree, the Fox air sleeve kits are a good deal considering, but I figured why not save a few bucks since I was already ordering seals anyway.

The reason I chose polyurethance for the shaft -110 was due to a Fox seal head assembly drawing I found and the seal in the shock I tore down was tan in color. I'm not an oring expert so I'm not sure of the difference between a buna 90 and a polyu 90, but I'm sure the buna is cheaper.
 
#3 ·
#4 ·
I'd suggest making your own slotted allen key, like the guy in that thread did. If I remember correctly, he just dremeled a slot big enough for the needle in the allen key, so he can tighten down the rubber pellet before removing the needle. Also, if you have the tools, you could consider just drilling it, tapping it, and installing a schrader valve.
 
#6 ·
Get the needle. As you say, you cannot get to 400psi with a shock pump and DIY fill needle. With a shock pump you can get to around 300psi.

I got the needle and 600psi guage for $60. I just take it with me to my local moto store and they hook it up and fill the shocks. When playing around with the valving I just use air at ~300psi.

Search for "nitrogen safety fill needle" and there's a number of online stores selling the genuine fox version.

If you pull your RP3 apart, let us know what reb/comp tune it is and what the shim arrangement is. I've collected some info on medium and firm tunes here. It would be good to get a database going of this stuff for future reference.
 
#10 ·
#14 ·
Good tip about the nitro tool. Might have to get one.

Regarding my own adventures (in http://forums.mtbr.com/showthread.php?p=8211652#post8211652) I just built that bike back together and updated the post. I plugged the rebound adjuster rod (internally) and ditched the platform functionality as well as re-arranged some washers on the main piston and everything seems to be working very nicely now.
 
#15 ·
Ok. Needle valve ordered (with schrader adapter) and should be here this week.

One question for you guys: where are you sourcing your damper O-Rings?
Or any of the damper seals for that matter? I've got the p/n's for individual O-Rings and 'kit' p/n's for the rebuilds, but Fox won't sell them outright. None of the shops can get them....
Looks like you guys across the pond have better access, but ordering such small parts to the states seems too expensive.

Are you just mic'ing the size/diameter and replacing with the like?

--------------------------------------------------------------------------------------------------------------
Ola H.
-saw your post on the rebuilt shock. One question though.... With only a couple hundered psi in the damper, how are you getting adequete rebound? I thought the rebound/pro-pedal were directly affected by the internal psi?
I have a document from Fox stating that the internal psi was to change from 300 to 400psi as of 2006. (this is for the RP3, RP2, RP23)
So with only a couple hundered I'm suprised you can even ride the shock....
 
#20 ·
Well i recieved the needle safety tool and was able to deflate my shock's nitrogen. I then replaced the rubber puck and was able to reach 300psi with my Fox pump. Held air just fine.
I'll be tearing into it shortly along with an older Talas R shock i picked up for $20 to use for donor pieces. Hopefully the Talas will have diff shims than my RP3 so i can play around.
The only mod i made to the needle tool was to shorten the needle. Dia is right, but length was too long. They're meant for large body shocks so a few mm's shorter worked fine.
Joe

sent from my hand-held computer
 
#21 ·
Couple of things to watch out for.

Depending on your bleeding technique, the IFP volume may increase as you purge out air bubbles so allow for it when you set IFP depth.
The bleed screw tightens down on a plastic pellet, not sure how many times the plastic pellet can be used before it leaks.

Your not going to have many options with the high speed compression, it uses disc springs instead of shims. The disc springs don't like to travel too much or they fatigue and break. If you want to use a single disc spring, try to shim it to make up the difference in compressed height.

In my opinion the compression tuning is not the biggest performance problem in the float shocks. Have a good look at the rebound circuit, seems to me Fox has constrained it so the propedal circuit is more effective. Pedal bob is up and down, the compression side of things is more obvious but look what happens to low speed rebound flow when propedal is engaged and the plunger blocks the hole in the piston bolt. Now picture what would happen if the HSR was too active, the propedal effect would be greatly diminished on the rebound side. I think Fox has chosen to set HSR on the constipated side to increase the effectiveness of propedal.

If your shock has been packing down in rock gardens and the rooty stuff you can drill those three HSR holes bigger but be careful, more port area equals more port flow as well as more surface area against the shims. Now the shims are going to open earlier as well.

One side effect of a too soft compression tune is that propedal will get used more often and that impedes LSR flow. The problem I had trying to tune these shocks is everything affects something else and its not always apparent how at first.
 
#22 ·
Good info.^
I've sucessfully rebuilt my RP3 & the girlfriends Float R.
I was able to tap the threads on a donor Fox schrader vavle and this is holding pressure just fine for the nitro chamber-300psi.
I'll get pics up soon of both shocks & their respective shim stacks. My '05 RP3 has some interesting valving...
I'm off to Miami for a wedding.
Joe

sent from my hand-held computer
 
#24 · (Edited)
Here we go....

Sorry for the 'Tease' and run post from last week. Had to travel and didn't have time to do a full 'n proper write up.
So, here we are. I recieved my 'Nitrogen safety needle' from Poly Performance the other week and proceeded to disassemble my RP3. This RP3 is a late '05 early '06 model from my Giant Trance. The Trance is also a first gen that I bought as a frame only from the lbs that same year.
*I will refer to the 'Nitro chamber throughout, even though I am filling with ambient air.
*I have reset the IFP to factory settings and pressurized the nitro chamber to 300psi.


The pressure that was remaining in my shock was pretty negligable as it sat. I had definetly lost some over the last ~5yrs. I had performed regular 'air sleeve' maint. every other year and not too long ago I fell victim to the ever common 'stuck-down' syndrom.
Now realizing that issue, I'm sure that's where some of the nitro snuck out.

Here is the vavling assembly.


Seems to have both firm comp. and firm rebound valving.

I was able to find a donor shock on CL for $20 that I figured at best could be used for internal parts etc. and worst case I'd have it for bushings. It was an ~'05 Talas RL rear shock. I disassembled that shock and to my pleasure I found the shims to be useable along with the schrader valve, O-rings, and many other small pieces.
Here is a pic of the Talas. Only used for shims and schrader


I realized after reviewing many exploded views and pics that the pos air schrader valve was a 36tpi where it threaded into the body. This is only important because the tpi for the grub screw (where the nitro is held) is 24tpi. So, I decided that I'd try tapping my donor valve to see if I could use it in place of the grub screw for the nitro chamber.
I realize that it seems mildly redundent to purchase the nitro safety needle and then try to fit a schrader valve for the nitro chamber, but I had only found a few saying that they had tried and found it mildly successful. Figured I'd give it a go since I had nothing to loose. Also had the advantage of working with the 1st gen Trance frame and I have MORE than enough room to turn the bottom of the shock body 180 degrees. Running the schrader valve for the nitro opposite the PP lever.

Also had a 24tpi Die at work, so this was a no brainer. I had no problems turning new courser threads into the finer threaded body. I had to turn down the 'hex' area that allows you to tighten the schrader, but after removing them I filed 2 flat spots to allow tightening.

*One thing to note. I had read where others had tried the schrader valve for the nitro and had a problem leaking due to the high pressures in there. After a few attempts at filling through the schrader valve I realized that I needed to tighten the valve 3/4 of the way, Fill to 300psi and tighten the valve down before releasing the pump. This effectivley 'pinches' the rubber seal the is behind the schrader valve. Therefor the valve is not responsible for holding the pressure, the rubber disk is.
Here it is holding pressure just fine.


Filled 'er up and went for a ride. Was a beautiful day before I was to leave on vacation and I had to see if I was successful. I had a great ride! 1st off, the shock NEEDED a rebuild in a bad way. I realize that after 5yrs of abuse the shock fluid was more than done for. So, with that in mind, everything rode great, the shock held pressure on both ends just fine and I'm glad to say that I was able to rebuild this RP3.



I then left for a weeks vacation (from which I just returned) and checked the air pressure in both the pos main body and the nitro chamber today. Both holding just where I left them. 175+psi and 300psi in the nitro chamber.

Here's a few thoughts since I've now torn the shock apart a few times and have been playing with the valving.
I noticed a couple years ago that my ProPedal lever had become slightly,...well...limp. Thats the best way I can describe it. When flicking it between the 1-2-3 position, it would just slide over without the same pazzaz as day one. Since the rebuild I realize this is directly related to the nitro chamber pressure. After doing the damper rebuild, but before pressurizing the nitro chamber, the PP lever felt the same. As I pressurized the nitro chamber the lever became firmer and more positive feeling. After tearing the shock apart a couple times now (having the nitro chamber air leak once and the lever going 'dead') I realize that the nitro chamber pressure is directly loading the damper and thus, loading the PP plunger.
So, if your PP lever feels 'dead' or 'limp' I'm gonna say that your shock needs a full rebuild to repressurize the nitro chamber. Just my observation. Now that I've rebuilt mine, it feels amazing when I throw it around.
Also, Fox offers great info on rebuilding thier Airshox line of shox for snowmobiles and ATV's. Refer to their detailed pics and descriptions for info on depressurizing the nitro chamber and also refilling.
 
#27 ·
1) IFP depth is 1.90" for my 165x38mm shock (6.5x1.5)
Set using a digital caliper.
2) I followed the procedure outlined in the Fox AirShox directions.
They specifically tell you to depress the piston assy. before refilling with nitro (air) and as the nitro chamber is filled the piston will rise to it's proper height.
Not to contradict what Tig said, but I've had zero problems rebuilding my shock this way.

And I'm running ~315 psi. This seems to work just fine. I havn't had any problem with losing pressure or the pos and neg air mixing.
 
#26 ·
Not sure what length shock is on the Trance. IFP depth on 165mm stroke Fox shocks is 1.9", IFP pressure should be 400psi.

Bleeding these shocks is extremely easy. Once IPF depth is set, fill damper to the brim with oil, remove bleed screw and ball on damper assembly, make sure damper rod is extended as far as possible, insert slowly into damper and excess oil will come out the bleed screw. Put ball and bleed screw back in place.

DO NOT cycle the damper until you have the IFP up to pressure.
 
#28 · (Edited)
Download this file and many (all) of your questions will be answered.
There are IFP depths, torque values, pressures, etc...

The Bible: http://sendspace.com/file/gp9k3p

Also, here is the site for the snow airshox: http://service.foxracingshox.com/powersports/index.htm
Look under 'rebuild procedures' for the Float & Float2 and the info will pertain to the MTB side of things.
Starting on page 15 of the rebuild describes the method I have used when rebuilding my RP3.

Joe
 
#127 ·
Fox Service Instructions RP2, ...

is unfortunately not available.

I assume it was a ZIP File with the service instructions for rp3, rp2, rp23 and others.

Please can someone upload it again?

www.dhfr.ru/fox , which I assume had the same information is offline, too.

I would appreciate it very much when I can get the "Bible".

Thank you
wildhai
 
#30 ·
Well I was able to put some good time on the bike lately and can say for sure that the action of the RP3 is greatly improved! The fork (2011 Manitou Minute) and RP3 are working together better than I have ever remembered.
The RP3 felt like it was tracking better through the rough and the minor shim changes I had made seem to help more than hinder.

I rebuilt the shock again after the ride and pressurized the nitro chamber as per Tig's instructions with no percievable difference. I'll be riding again tonight to confirm.

The only thing I noticed was that I lost a little of the rebound adjustment 'range.'
Meaning that the rebound is still controllable, but doesn't have as much adjustability.
This may be due to the fact that I added a few shims to the comp stack and this may have pushed the piston a little too far away from the rebound needle. That is the only thing I can come up with.
Otherwise all is well. The PP still has a percievable difference between 1-2-3 settings.

Joe
 
#32 ·
So the procedure is:

1) Insert IFP and set it at the correct depth.
2) Fill with oil and carefully insert piston assembly. The piston should be just below the oil. Stroke it slowly so air escapes and then thread main cap avoiding any air entrance (using bleed screw?)
3) Compress the shock to verify IFP depth (no interference)
4) Fill it with nitrogen/air.
5) Grab a beer

Seems the safety needle + 400 psi regulator + nitro tank + 7mm o-ring chord for plugs is the "factory" method.

Sounds good?
 
#33 ·
So the procedure is:
...
3) Compress the shock to verify IFP depth (no interference)
4) Fill it with nitrogen/air.
...
Do not compress the shock without fill pressure in the IFP so 3) 4) becomes:

3) Fill IFP chamber with nitrogen
4) Compress the shock to verify IFP depth (no interference) - optional - you'll need a hand dynamometer or other lever-type setup - if IFP is set right there will be no interference
5) Fill it with air
 
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