# The Fox Float RP2(3) damper service thread: uncovering the secret.



## One Pivot (Nov 20, 2009)

I was never happy with the performance of my float RP2, or with the fact that i cant service or tune it. It ended up getting replaced by a much better shock, but this left me with a spare hanging around.. i figured this was time to figure out whats happening in this shock, so i cracked it open. 

hopefully this will serve as a guide for future users to service their own RP fox shocks at home, and tune them to their weight and style. i dont want to get too optimistic yet, but i think i can figure out a way to turn an RP2(3) into something like an RPC, adjustable LSC compression! ill have time for pictures tomorrow. 

the fox RP2 damper is complicated. I dont want to say sophisticated because i dont think it really works that well. Its sort of a two stage compression piston damper, but neither are floating pistons, just two static pistons. It accomplishes this by a perforated foot bolt on the compression piston. 

The first piston blocks off the compression piston, but not in a typical fashion. It uses a large steel washer (not shim) to plug off the port, followed by concave spring washers to preload the rigid steel washer. These spring washers offer not quite a platform, but sort of a threshold for damping. Once compression forces the fluid to open up the first spring washer assembly, oil flows past it. From here it flows into the perforated foot bolt and into the center of the upper compression piston where it flows through an orifice and out a conventional shimstack. leaving propedal open bypasses the lower wave plate. 

it looks like only a small amount of oil actually hits this upper compression shim stack, while the rest just bypasses the piston completely if the lower spring washer opens enough. this theory is inline with how the shock feels (blows through travel, poor midstroke). its damping using nearly a port orifice until thats overcome then it switches to a shim stack until thats overcome, then it just blows open. i dont see anything related to a circuit to control bottom out. 

this leaves bottom out control to be a function of the air can.. requiring the air can to ramp up the spring rate and leave an oversprung/under damped shock and hope the rebound circuit can control the kick back (admittedly, the fox rebound circuit seems to work very well). 

it appears that the rebound circuit is a conventional shim stack arrangement.. which works. why not a conventional shim stack compression circuit?? 

im pretty sure the lower piston can be removed completely in favor of a easily tunable, smooth and controlled shim stack. in theory this means you could, on a lot of bikes, remove the small air can for the larger one and use damping as a means to control bottom out, instead of spring rate... like a coil shock does. 

this leaves us with the IFP. i have no idea where the ifp was, it clonked into the bottom.. this will need to be set. theres calculators online to use, unless someone wants to pony up that well kept secret. a shrader valve and short tube arrangement should make filling the IFP chamber a breeze, and allow for ifp pressure adjustment, also to control bottom out. 

keep in mind, this is all my theory from what ive gathered from a torn down RP2. feel free to fact-check everything or contribute your thoughts to the operation of the circuits. ill take pictures and post them this week. 

ideally this thread will end with a start to finish guide to disassembling, tuning, and charging and reassembling the Fox Float RPx series shocks at home! your contributions are appreciated!


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## Scotth72 (Mar 15, 2004)

As far as I know, IFP pressure only controls bottom out when it acts on a position sensitive valve, such as Fox's Boost Valve or SPV. With a shim stack, it mainly controls cavitation. It does provide some spring ramp up from the shaft displacement, but I don't think that will prevent bottoming. 
I have read the schematics for the Float series, its nice to hear a description to go along with the diagrams. I was real curious about the Belleville washers for damping, they would provide a real regressive damping curve.
I do believe your bottom out concerns have been addressed with the 2010 BV shocks. I understand it has a valve that is affected by IFP pressure, and so is position sensitive. 
As far as adjusting IFP pressure at home, a schrader valve would work, but then you could not service the air can without removing the valve.


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## Deerhill (Dec 21, 2009)

I thought the nitro charge had to be done in a chamber so nobody gets hurt.


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## GrantB (Jan 10, 2004)

A. Awesome. Keep on going and tell us what you learn.

B. Photos?


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## One Pivot (Nov 20, 2009)

nitro charge.. atmospheric air is mostly nitrogen. the problem with compressed atmospheric air is the moisture content. rockshox doesnt think its an issue and sells a tool to charge your own shock with a shock pump. im buying into rs's advice. 

im making some assumptions about bottom out and IFP's based on what i know about forks.. it may or may not apply, i dont know. the DHX and similar piggy back shocks use it in that fashion. even if i couldnt get it to control bottom out at all, id be plenty happy having a easily shimmed fox shock. 

thinking about it, the compression damping ports on the piston are HUGE. i think too big for a shim stack. gonna think of something creative. push is replacing the pistons when they do their work arent they? i think i can see why! 

more later..


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## thebronze (Jan 13, 2004)

If you dont want the platform mech, why not just sell it and get a DHX or a regular float? You can play with the shim stack on either of those. Doest make much sense modding a top shelf shock to get a simple shimmed damper unit. There's probably plenty of people here who would trade up with you.


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## Mr.P (Feb 8, 2005)

Great post One Pivot! Thanks! Looking forward to the pics 

IFP can act like a small ramp up for both damping and spring rate, but it also increases internal pressure. It's purpose is also to give a air-free space for oil to fill as the shaft takes more volume in the oil chamber (probably it's primary purpose).

A coil has an IFP to control some BO, but that is already assuming a correct spring rate, and a coil has a nice ~1 inch thick solid BO bumper which controls end of stroke ramp up.

Also keep in mind that a small chamber air can has a progressive spring rate unlike a coil, that can be quite an advantage. for example:
travel | coil | air (spring rate)
25% | 100 | 75
50% | 200 | 125
75% | 300 | 300
100% | 400 | 500+

So in an air spring, initial travel can be more active on smaller bumps due lesser spring rate into mid-range travel, yet ramp up high for drops and other bigger hits.

I agree that it is odd that air spring is the only real BO control, but like you said Fox's rebound damping is so good it handles it well. So well for me, I see it as a non-issue. But a lot is dependent on the designed linkage shock rate)

RP2 in action, stock (Specialized custom tune(?)) No BO so far, supple on the small stuff.

P


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## Mr.P (Feb 8, 2005)

*Fox RP shock air chamber service pictorial instructions*

Fox RP shock air chamber service pictorial instructions

From BikeRadar.com

Should be a good match up with this thread.

An excellent write up with many pics
http://www.bikeradar.com/gear/article/workshop-fox-rp-shock-service-25701

P


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## Deerhill (Dec 21, 2009)

" i dont want to get too optimistic yet, but i think i can figure out a way to turn an RP2(3) into something like an RPC, adjustable LSC compression! ill have time for pictures tomorrow."

Cool thread Pivot. I always thought the low speed comp was ok on my HL bike.

My RP2 spikes, and is not be able to keep up at high speed when the tires are on the ground (it does an ok job on the landings tho). I think a cool way to modify the RP2 would be to ditch the lockout, and use the switch for LSC and HSC. That way I could flip it wide open for the way daown. Would love to see your thoughts on this problem.


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## YnotGorilla (Mar 22, 2008)

I`d like to revive this short-lived thread.

RP23 HV cutaway:








I`d like to remove air from the compression unit in my 4 year old RP3, it is my impression that this can be done through port 1 & 2 (port 2 is located on the side, parallel to the eyelet), port 3 is for IFP, and port 4 is for rebound spring+ball, is this right? 
The ports are arranged in a similar fashion on RP3.
The bleeding procedure has been thorugly described for DHX, so I guess one can use the same procedure here when the right ports are identified.
This procedure would require recharging the IFP? (replacing nut with a valve?)
Regards,
T

Thought I`d add a ride pic from last weekend in the end to cheer you up on a rainy Saturday (I guess those on the forum are not out riding for a reason..)








Hardanger, Norway


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## presslab (Jan 5, 2007)

How did air get in there? Probably a bad o-ring on the IFP, you'll need to fix that.

Looks to me like port 1 is for the air pressure. Port 3 is to bleed the fluid. Not sure about the others. To recharge the IFP you could put a schrader valve on there, might cause problems fitting it back to the bike frame. Or you can use a hypodermic needle.

Maybe this helps you:
http://forums.mtbr.com/showthread.php?t=23924


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## YnotGorilla (Mar 22, 2008)

OK, Thanx for the link. So IFP is at the bottom with port 1, the compression circuit is between 3 and 2 or 4. 
Anyone got a guess for the IFP length for 7.785/2.0?


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## Scotth72 (Mar 15, 2004)

Port 1 is your nitrogen port. IFP depth should be 2.25 inches from top of shock body. #3 is the oil bleed port, keep this open while you insert piston into shock body, letting air out of system. Make sure you don't misplace the little metal ball under the screw. You really don't need to mess with the PP and rebound knobs, unless you think you have a bad o-ring. Watch for tiny check balls and springs.
IFP pressure should be around 300 psi. You will need a new rubber seal plug, a needle, and preferably a regulated nitrogen setup. You could do it with a needle and shock pump, but you still need a way to keep 300 psi in the shock while getting the needle out. 

The compression circuit is on the piston itself.


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## One Pivot (Nov 20, 2009)

ive been lagging, the shocks still apart. honestly ive been so impressed with my isx6 that ive almost completely given up on fox air shocks. the isx6 is so drastically better i cant see transforming the rp2 to being even close.. not much motivation to keep going with it!

the rp2 has 2 compression circuits, the first is a belleview washer kinda setup. its also ported through the center shaft to a top piston with more shims. i think it would work better if you gutted the whole compression assembly and installed a new piston and a real shim stack. i think thats what push ends up doing with them anyway? i believe they change the piston either way. 

the arrangement explains why the "high" compression floats still use quite a bit of travel and still feel harsh. its not consistently damping at any time.

if you undid the bleed port without deflating the IFP you'd spray 300+ psi oil out! at best you'd make a horrible mess, at worst the screw would go shooting out and possibly hurt you.


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## Scotth72 (Mar 15, 2004)

Push does indeed put a shim stack in instead of the belleview washer and plate that comes stock. They use a different piston as well. My RP3 is a Pushed model from 2005, it had a preloaded shim stack with all the same size (large) shims. I don't know if they are valving them different these days.

The shims on the top piston are just check valves I believe. You could probably play with the shims somewhat to control low speed flow, but they are mostly there for bypass. 

The PP knob preloads the compression free bleed valve, either letting oil bypass the shims through the check valve, or forcing it through the shims on the main piston.


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## One Pivot (Nov 20, 2009)

my pp valve had 3 or 4 washers behind it, im assuming thats how they "tune" propedal? its going on my girlfriends (light rider) 2:1 bike, it needs as little compression as possible!


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## Scotth72 (Mar 15, 2004)

I guess so. I think its a combination of that, and how much they preload the belleview washer. I know that the higher tunes have more shims/spacers behind the washer on the main piston. The little tiny spacers behind the little piston are also there so that you can have the correct throw when the whole assembly is put together. With different shim arrangements, the distance from the adjuster to the end of the piston changes, so you need to take that into account. The PP/rebound adjustment range is fixed, so you have to make sure that you have the full range of movement using the spacers. The rebound has a similar arrangement elsewhere in the assembly.

You space the damper for 9 clicks of rebound, and just a bit of free play on the PP valve when fully open.


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## thebronze (Jan 13, 2004)

One Pivot said:


> my pp valve had 3 or 4 washers behind it, im assuming thats how they "tune" propedal? its going on my girlfriends (light rider) 2:1 bike, it needs as little compression as possible!


Sounds similar to the marzocchi tst2 stock setup. The washers closed the compression ports on the piston and allowed the low speed port to control the damping. Once the washers were removed and a firm shim stack put in place the low speed bleed became a low speed adjuster. Stock setup was incredible spikey. Modified setup w shims was much better. You may be able to do something similar with the rp shock.


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## One Pivot (Nov 20, 2009)

the pp its a spring loaded valve, its not really a shimmable piston or anything.


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## Dougal (Jan 23, 2004)

One Pivot said:


> the pp its a spring loaded valve, its not really a shimmable piston or anything.


Propedal is simply a one-way ballvalve on the rebound circuit so oil can't go that way on compression. So it makes the oil go through the shims.

The adjustments on the RP shocks are simply have a variable pop-off on the compression side of this, the lever changes spring force on the ball that prevents oil going up the middle and around the piston.
Move the lever around and it compresses or relaxes that spring.

That's all it really is. The rest is a typical shim stack where you can do what you like.

Air can get sucked in through the main shaft seal if the IFP pressure isn't high enough. Basically the pressure on the shaft seal gets a load reversal and it burps a little air. Does it often enough and your shock gets all slurpy.


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## One Pivot (Nov 20, 2009)

its not a typical shimstack though.. whats going on with the belleville washers? oil hits that before hitting the more conventional, but still weird second shimmed piston. even on that piston, oil flows out from the center of the shaft instead of from under the piston. i think its damping the port orifice oil flow while the belleville washers act as a blow off of sorts? its a weird arrangement.. i dont think it works that well.


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## Deerhill (Dec 21, 2009)

One Pivot said:


> its a weird arrangement.. i dont think it works that well.


just ditched mine, I liked the ramp up for landings but anything technical at speed and it chokes


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## mtg7aa (Jul 11, 2008)

Great thread, but we need some good pics of the damper internals! The cutaway view is good, but it's still tough to decipher what is going on.


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## Brighter-Lights (Oct 5, 2008)

Apparently, it's quite common for Nitrogen to leak past IFP into the damping oil. Wouldn't it be better to replace IFP seal (o-ring) with a X-ring/quad ring? 

What would happen if you remove IFP completely and will the whole chamber with damping oil? As to bypass the nitrogen filling issue...?


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## Scotth72 (Mar 15, 2004)

If you filled the shock completely with oil it wouldn't compress. The nitrogen chamber is there to allow for shaft displacement of the oil.


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## Dougal (Jan 23, 2004)

Brighter-Lights said:


> Apparently, it's quite common for Nitrogen to leak past IFP into the damping oil. Wouldn't it be better to replace IFP seal (o-ring) with a X-ring/quad ring?
> 
> What would happen if you remove IFP completely and will the whole chamber with damping oil? As to bypass the nitrogen filling issue...?


I haven't found that problem soo much. I did have a RS shock back in the day (well 5 of them actually, warranty, warranty, warranty) which would have the floating piston flip itself around, letting the nitrogen and oil swap places completely.

At least one of those warranty shocks arrived with no nitrogen pressure in it at all. This allowed the shock to suck air in past the shaft seal on fast hits. Which is the other function of the nitrogen charge, to keep positive pressure on the shaft seal at all times.
After one ride with no charge pressure, the shock had sucked itself completely full of air.


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## BC (Jan 11, 2006)

I did this mod a while back,so I'm a little fuzzy. hope this helps.

I typically have to de-valve my shocks to make them more active to my liking (and my weight 137 lbs).

I removed 1 of the conical washers, 1 compression shim, and 1 of the tiny PP spring pre-load shims. This helped a lot with reducing the platform feeling, Sliding the whole compression range to the lighter side of things. The PP also acts somewhat as a check valve for rebound flow, so the PP valve needs to stay functional (at least in this configuration). Removing more than one of the PP shims leaves some "slop" between the valve and valve face with the PP lever off, and there will be very little/no damping. Since the PP circuit is in series with the main compression stack, I think total oil velocity/volume flow is going to be limited by the PP orifice and thats as good as it well get. I think it's a decent shock and works as designed, but it's still an air shock with a air spring curve. I bought it as a backup to my coil and it was super cheap.



Uploaded with ImageShack.us


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## TigWorld (Feb 8, 2010)

Great thread. I've just finished revalving my daughters RP3 for her svelte sub 40kg weight and was able to compare the shim stacks in a standard and firm tune RP3. I've made a few mods to LAKESNAKE's pic to clarify a few things.










I've got the full run down on what I did here but I've not included any how-to info on disassembly etc and no pics. If you need that sort of info then I think you need to do some more background research before giving a revalve on one of these a go.


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## PMK (Oct 12, 2004)

When additional shim diameters and thicknesses are available, even better results can be obtained.

As can be seen, there is very little aspect ratio to the stacks, and a tuner has very few shims to work with. 

PK


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## thuren (Jul 29, 2009)

Pulled my RP2 apart and added std shims, instead of that goofy pop-off plate and conical washer. The pop-off guide was .050" thick, so I added .050" worth of 1/4"IDx.010" shims. Works perfect, and much better high(shaft) speed feel. Very happy with the shock now. May even go stiffer.


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## thuren (Jul 29, 2009)

kan3 said:


> Happen to recall the OD?


The disk measures 21.5mm, and a 22mm shim has plenty of room IIRC.


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## kan3 (Nov 11, 2009)

thuren said:


> Pulled my RP2 apart and added std shims, instead of that goofy pop-off plate and conical washer. The pop-off guide was .050" thick, so I added .050" worth of 1/4"IDx.010" shims. Works perfect, and much better high(shaft) speed feel. Very happy with the shock now. May even go stiffer.


Happen to recall the OD?


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## GlenH (Jun 21, 2007)

How are you guys who have tuned your rp2/3s re charging the IFP chamber?

Are you using a shock pump and charging with air, or using nitrogen?

How are you getting it in there? Using a needle or by replacing the rubber seal with a valve?


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## thuren (Jul 29, 2009)

I made up a charge needle for my nitrogen tank. You basically loosen the nut a little to release pressure from the silicone/rubber disk, insert needle, pressurize, remove needle, tighten nut down, then leak check.

It's a little finicky be careful with the needle.

Also, make sure you insert the needle dead center, as the hole on the backside of the disk is small.


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## donpinpon29 (Dec 30, 2009)

im going to put in the place of the disc a schrader valve so I can experiment with different pressures


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## Dougal (Jan 23, 2004)

donpinpon29 said:


> im going to put in the place of the disc a schrader valve so I can experiment with different pressures


It is very difficult to seal up a schrader valve stub well enough to hold the 500psi necessary.


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## donpinpon29 (Dec 30, 2009)

Ok thanks for the advise.
Just for curiosity, isnt the dhx5 holding the same pressure in the piggyback with a schraeder valve? 
And wondering of the real pressure for a 200 x 50 rp2:
Tacubaya advised 400 psi
Others say 200-300
You advise 500 psi
Thats why I was trying to put a schraeder valve, to try different pressures not to suck air through the seal into the oil chamber.


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## tacubaya (Jan 27, 2006)

donpinpon29 said:


> Ok thanks for the advise.
> Just for curiosity, isnt the dhx5 holding the same pressure in the piggyback with a schraeder valve?
> And wondering of the real pressure for a 200 x 50 rp2:
> Tacubaya advised 400 psi
> ...


Fox used to charge them at 300 psi before emitting an announcement to all service centers advising a 400 psi charge on all Floats. People are using 300 psi because that is usually the maximum they can put in with a regular shock pump. My nitro tank regulator allows me to inflate to 400 psi easily.


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## Dougal (Jan 23, 2004)

donpinpon29 said:


> Ok thanks for the advise.
> Just for curiosity, isnt the dhx5 holding the same pressure in the piggyback with a schraeder valve?
> And wondering of the real pressure for a 200 x 50 rp2:
> Tacubaya advised 400 psi
> ...


I can't recall right now what pressure my DHX5 runs, but it's less than 300psi, nowhere near the 500psi. Mine does lose pressure, not sure from or exactly how fast but if I go out now and check it, it will be down to nothing. It's on a bike that doesn't get ridden much. The DHX however seals properly with an o-ring around it's shrader valve. Getting a good seal between the thread and the shock body is very difficult when retrofitting schrader valves to fox shocks.

I don't have an RP2, but 300psi isn't enough for the Float R rear shock I have here, it sucks air in through the seal head with that much pressure. 400psi is pretty common, 500psi is recommended for some shocks.


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## Sagnak (Jan 26, 2012)

hi guys 

so is this 400 psi the proper pressure for sure ?
I have a regulator that can charge 60 bars like 800psi
so whats the final decision here below is the calculation for return forces of the shock side (without the air side )

300psi 15kg return force
400psi 20kg return force
500psi 25kg return force


all above return forces are calculated with a 9.52 mm diameter shaft (rp2 200x50)


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## el_roy1985 (May 29, 2008)

Just pulled my RP2 a part because it was leaking oil through the pp lever. Can anyone tell me what oil to use and how much( if I can use something other then the fox fluid)? Also, should I look for special orings? 

Ordered a new RP2 so I could rebuild my old one at my leisure, but they sent me the wrong size. So now I'm pretty bummed I have nothing to ride till I get this figured out.

Any other tips/tricks to re-assembly would be greatly appreciated as well...


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## 1niceride (Jan 30, 2004)

Read all posts on this subject going back as far as the forums allow. Don't screw with it until you do. Ifp depths and all. Might take couple of weeks to get through it all. 

I've serviced 5 fox shocks and converted all to air valves so I can use my shock pump to charge the ifp chamber to 350 psi. 

My RP3 I bought new had a weak ifp charge. I discovered this after converting to air valves and pumping in 350psi. The PP lever is really crisp when switching now. I bet many fox shocks are down on ifp pressure. 

Let us know when you open it up.


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## el_roy1985 (May 29, 2008)

I already have the shock pulled a part. Just have to source the parts I need, along with finding the correct re-assembly procedure. Along with finding out how to convert to an air valve.

I'll do another search, but this is the most informative thread I've been able to find so far. Haven't seen anything on the IFP depth (guessing that is the white disc between the fluid area and nitro area), so if anyone could point me in the direction of the information, that would be great.


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## 1niceride (Jan 30, 2004)

I set my 1.5's at 50mm. I lost the link to a crash but the info is here somewhere. 

Made the air valve by threading the other end of a long tire valve for a truck 5/16x24.


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## el_roy1985 (May 29, 2008)

What are the 1.5s at 50mm?

Did another search, but still not finding anything useful.


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## 1niceride (Jan 30, 2004)

1.5" travel set at 50mm deep.

I don't think you are ready for this...yet


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## el_roy1985 (May 29, 2008)

Your right, because that isn't making sense to me at the moment.

It is a 2" travel shock. Are you saying you had it pushed in at 1.5" of it's travel, but then where does the 50mm come from... 

The shock itself seems pretty easy to figure out, I just don't know what your measurements are for.

Right now I'm trying to figure out a way to get the internal shaft removed from the top shock cap. I've got PB blaster soaking into it in hopes that it will loosen the glue (at least I think I read that's what's holding the threads) so I can get it off. Then I can get the o-rings replaced and start worrying about re-assembly.

Sucks that Fox couldn't make this shock serviceable by the end-user. I'm certainly not gonna pay $100+ in maintenance every 200 hours of riding as they suggest.


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## 1niceride (Jan 30, 2004)

With fox 1.5" travel shocks,most anyway. need the ifp set at 50mm from the top of the tube. 

2" travel shocks further down so the piston doesn't hit the ifp separator at full travel. 

When I did my Noleen crosslink shock I set the ifp separator just past the piston at full travel, no oil. Just for kicks I did that with my fox van and then measured the ifp depth and it read 49mm. 

You need 2 wood or alum or brass blocks with a hole at the seam to grip the shaft. Squeeze the blocks together to hold the shaft. Are you sure you read all the info about this??

These shocks don't stay right for very long if used alot.


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## 1niceride (Jan 30, 2004)

By the way...when you set the ifp at its depth for final assy, put the rubber puck and set screw in tight to hold the ifp in position before proceeding. The very last thing you will do is put in your air fitting and pump to 300 psi.


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## el_roy1985 (May 29, 2008)

I knew I needed some specially drilled blocks to get the rod off, was just trying to do it without, being I don't have the tool yet. Will hit up a hardware store today for the materials to make it.

I also found another good thread with listed IFP depths. Should have this thing goin back together tomorrow. Probably take some pics of the process too, since all their seems to be is disassembly pics posted online.

Also, wasn't it said that 300psi is not enough. I keep reading anywhere from 4-500psi is hwere it needs to be...


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## el_roy1985 (May 29, 2008)

Drilled a block of wood and got the shaft unscrewed. Wasn't enough grip at first, but sprayed some brake cleaner on the wood before clamping and it held real nice. Spent the entire day searching down o-rings. For now, I think I will do without the PP and block off the spot for the PP rod with some o-ring bits.

Here is the question though...

With the PP rod gone, the spring and blocker (for lack of a better term) will be gone as well. Wouldn't this effectively lower the compression damping as well? That's unless the spring has such little tension when open, that it really doesn't matter anyways. The latter being what I'm guessing is the case.

Good news is, I have found an o-ring supplier that has the correct sizes for the shock. It's called, the o ring store (can't post links yet) . I will probably order the ones I need to add the PP function again next time I pull this bugger a part.

Going to get a few orings to chop up tomorrow. Need one to delete the PP and another for a new nitrogen plug.

Oh, that brings me to another thing. Got a hypodermic needle at the local farm supply and JB welded it into an airline fitting. It's an all metal one, so this should be pretty solid. Just surprising that you have to push so much pressure through such a little hole. Probably going to be easing the pressure up with the regulator.

So tomorrow I'll probably have pics and more info. Hopefully even a functioning shock.


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## skywaybuzz (Dec 31, 2003)

El Roy PM Sent


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## el_roy1985 (May 29, 2008)

Looks like I was wrong on the o-ring supplier. They don't have the o-ring for the PP rod. Maybe if I message them, they could do something for me...

Right now I am stuck at filling the N2 chamber. Was trying to find an air valve to screw in there, but so far that has not gone well. Can anyone tell me where they got there air valve and what they had to do to get it to fit? So far everything I've seen at parts stores is too big, and the one I have at home here is too small and no one seems to have an adapter that goes down that small...

Also, the other thread about servicing the RP2 has mysteriously disappeared. Had some good info in there too...


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## 1niceride (Jan 30, 2004)

Go to the auto/tire store. Look for a long stem valve about 1" or longer. Cut it at 1" long. Thread the unthreaded part 5/16x24tpi, about 5/16 of thread. It will screw into the shock body and will accept a shock pump. I have made 5 of them with no problems. Except one has to pull the valve to put on the can or spring.


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## el_roy1985 (May 29, 2008)

Wow, that couldn't have been much more obvious. Guess I've never done anything where I cut my own threads before, so didn't really think of it.

That was the final thing I had to figure out, so I'll hopefully have this done tomorrow. Even after having it together and a part a few times already, I forgot to take photos. I need to have someone to take photos for me or something, because when I get working, I usually don't stop till I'm done.

This shock really isn't all that complicated. Just a shame it's not likely you'll be able to get the o-ring for the PP rod. Guess I'll see how it is without PP. I didn't really care to use it much anyways.


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## 1niceride (Jan 30, 2004)

el_roy1985 said:


> Wow, that couldn't have been much more obvious. Guess I've never done anything where I cut my own threads before, so didn't really think of it.
> 
> That was the final thing I had to figure out, so I'll hopefully have this done tomorrow. Even after having it together and a part a few times already, I forgot to take photos. I need to have someone to take photos for me or something, because when I get working, I usually don't stop till I'm done.
> 
> This shock really isn't all that complicated. Just a shame it's not likely you'll be able to get the o-ring for the PP rod. Guess I'll see how it is without PP. I didn't really care to use it much anyways.


It might not leak there once you put in 300 psi or more. I think the PP bleeds into the low speed shims, I think. With the air valve you have many options to play with. I would leave the PP as is imho.


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## el_roy1985 (May 29, 2008)

The PP bleeds right out through the PP lever if the o-ring is bad. Mine definitely didn't look good when I took it out, so I shoved some o-ring bits in where the PP rod went. Hopefully get some riding in this week to test it out and see how I did with the rebuild and see how the fork oil performs that I got locally.


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## TigWorld (Feb 8, 2010)

The damping fluid in the shock is under at least as much pressure as you put in the IFP (more when the shock compresses). Plugging the PP adjuster rod space with o-ring bits is unlikely to be able to seal the 300-400psi you'll need in the IFP to stop cavitation.


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## el_roy1985 (May 29, 2008)

Just got back from a test ride. Seems to be doing pretty good so far. Not a single leak, but I think I added a little too much pressure(not to the IFP, I set that at 400psi). I also need to do the mod to cut down on the volume of the shock, because I've always felt that shock was too soft and adding more air just doesn't produce the desired effect.

As for the O-ring. It was an extremely tight fit. I even tried jamming it further in, but it wouldn't budge past where I got it. So I think it will hold for at least a little while. In the mean time, I will save up for a new rear shock and this one will only be used for backup.


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## One Pivot (Nov 20, 2009)

TigWorld said:


> The damping fluid in the shock is under at least as much pressure as you put in the IFP (more when the shock compresses). Plugging the PP adjuster rod space with o-ring bits is unlikely to be able to seal the 300-400psi you'll need in the IFP to stop cavitation.


The IFP doesnt push fluid through the PP orifice. The whole thing is under pressure.


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## TigWorld (Feb 8, 2010)

One Pivot said:


> The IFP doesnt push fluid through the PP orifice.


I never said the IFP pushes fluid through the PP.



One Pivot said:


> The whole thing is under pressure.


That's what I said. The damper fluid is under whatever pressure you put in the IFP, and more when you compress the shock. The seals on the adjuster, rod and damper shaft need to stop damper oil leaking out under that pressure.

With the rod in place, the pressure in the IFP helps to push on the adjuster rod and keep things sealed up.

If the bits of o-ring work for el_roy1985 then great.


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## pitioa (Aug 8, 2012)

I have read this post but I have a little doubt.
My shock is a rp2 and it is leaking by the adjuster knob, so one question the oring that I need to replace is the one on top of the rod? Just to be more clear in one end of the rod you got the piston and
valving and in the other end is the oring
Also is this the hard to get oring?


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## el_roy1985 (May 29, 2008)

The ring isn't hard to get, it's pretty much impossible to get. If anyone does find it, please post where!

The o-ring is on top of the inner most rod and the shcok has to be completely disassembled to get to it.

My next shock will definitely be one with rebuild parts readily availabe. This shock is too high maintenance for a shock that they wont even provide you parts to rebuild it yourself. I refuse to send my shock in to pay $100+ every time the oil needs to be changed or the PP ring starts leaking (which seems to be very common). Then you have to wait a few weeks to get it back on top of that. Screw that...


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## pitioa (Aug 8, 2012)

el_roy1985 said:


> The ring isn't hard to get, it's pretty much impossible to get. If anyone does find it, please post where!
> 
> .


:madman:


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## StreamRider (Jun 18, 2010)

There are at least 5 shops that rebuild the shocks. The o-rings must be available. Would be nice if a rep from one of those shops would give a hint.


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## pitioa (Aug 8, 2012)

I found them on ebay!!!!!
Item number: 160636313272


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## el_roy1985 (May 29, 2008)

pitioa said:


> I found them on ebay!!!!!
> Item number: 160636313272


Interesting. Guess I'll probably be ordering one tonight after I take another look when I get home. Sure cost enough...


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## pitioa (Aug 8, 2012)

About the IFP dept you can just put everything together without the oil and push down the piston so the piston sets the dept and then just push one or two milimiters in?


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## el_roy1985 (May 29, 2008)

pitioa said:


> About the IFP dept you can just put everything together without the oil and push down the piston so the piston sets the dept and then just push one or two milimiters in?


Someone said that they did that and it worked out. If you have the 7.875 x 2.00 RP2, then the depth should be set at 2.25 inches.


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## Dougal (Jan 23, 2004)

el_roy1985 said:


> Looks like I was wrong on the o-ring supplier. They don't have the o-ring for the PP rod. Maybe if I message them, they could do something for me...
> 
> Right now I am stuck at filling the N2 chamber. Was trying to find an air valve to screw in there, but so far that has not gone well. Can anyone tell me where they got there air valve and what they had to do to get it to fit? So far everything I've seen at parts stores is too big, and the one I have at home here is too small and no one seems to have an adapter that goes down that small...
> 
> Also, the other thread about servicing the RP2 has mysteriously disappeared. Had some good info in there too...


You will have to make/modify your own. But I have found that nothing seals as well or as easily as the rubber pellet system. I have fitted air-valves which when submerged in water don't show any leaks, but over a few months have still bled out all the pressure within.

Just like my DHX5. Everytime I check the pressure, there is none.


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## tune (Aug 27, 2011)

Dougal said:


> But I have found that nothing seals as well or as easily as the rubber pellet system. I have fitted air-valves which when submerged in water don't show any leaks, but over a few months have still bled out all the pressure within.
> 
> Just like my DHX5. Everytime I check the pressure, there is none.


That's weird. I have found the exact opposite. Many years old shocks with schrader valve doesn't show any noticeable pressure drop but when looking at a rubber pellet sealed Fox shock pressure has dropped significantly. Of course it's a different case if there is any dirt in schrader valve core...


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## pitioa (Aug 8, 2012)

Jeffery427 said:


> I thought the nitro charge had to be done in a chamber so nobody gets hurt.


It is the same as using compressed air


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## el_roy1985 (May 29, 2008)

pitioa said:


> It is the same as using compressed air


I think he means because of the high pressure, not just being nitrogen.

I also wondered if doing the filling in a 'blast chamber' was needed. Although, the pressures ramp up even further while riding. So I would guess the chances of blowing while filling to 400psi are a lot less risky then it exploding while hucking yourself off of drops on the trail. So far no one has had one burst while riding, so I don't think it's much of a worry at all.

Only advice I would have is to fill it gradually. Which you will have to do if you use a shock pump. If you use a nitrogen tank, I would just slowly turn up the regulator to prevent too quick of a fill that could cause possible failures not only in the shock, but in the tool you are using to fill the shock.


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## tacubaya (Jan 27, 2006)

I've never heard of a shock or filling needle blowing due to nitrogen charging...


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## ballistikmg (Oct 26, 2009)

*Filling the IFP without disassembly*

Can I fill a low IFP with a nitrogen recharge needle without disassembling the shock and still get good results or does the IFP first need to be serviced and depths set then refilled.


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## ballistikmg (Oct 26, 2009)

Can I fill a low IFP with a nitrogen recharge needle without disassembling the shock and still get good results or does the IFP first need to be serviced and depths set then refilled. Sorry for the repost.


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## 1niceride (Jan 30, 2004)

If it were mine..if no air in oil and no evidence of oil leak, and you got a way to charge it, what the heck..go for it.


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## donpinpon29 (Dec 30, 2009)

If you havent lost a drop of damping oil, I think its ok not to oPen it


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## old al mountain man (Apr 1, 2013)

If the shock is in the 2008 age rp2, could the valving be going bad, when it seems to be loosing some of its propedal sensativity? Seals are almost new, shock worked great until a couple of rides ago, then propedal threshold seemed to not react abruptly, like it used to. Checked for air leak, but none leaking out, no oil residue either. And shock length is what it is supposed to be. The levers and rebound seem to be working. Could unit just plain need internal shock tube valve service? All that was ever serviced was the air canister seals and nylon washers.


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## Rodeodave (May 11, 2013)

Just in case anyone still comes here:

https://www.bilder-hochladen.net/files/big/dt8m-1.jpg


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## chopperhause (Apr 26, 2013)

*rp 2 modification*

This is my rp2 , no spend money and all my problems about tunning solved .







I do with my shock what i want , not official service wants .


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## ShirleySerious (Mar 8, 2013)

chopperhause said:


> This is my rp2 , no spend money and all my problems about tunning solved .
> View attachment 804655
> 
> I do with my shock what i want , not official service wants .


Where did you get your schrader valve? It looks different than the one TigWorld linked to the other day. Here is a link that will take you to an off-the-shelf schrader valve that fits. Looks like there is also an RP2 and RP3 rebuild guide.


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## ncerni (Aug 6, 2013)

*PP rod o-ring*

I bought pro pedal rod o-ring at our local bearing/seals distributor. Size is 2.5x1 mm


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## Magnum9 (Jun 8, 2011)

So if I wanted to firm up the pro pedal on a 2011 RP2 with only the on/off switch, what would need to get changed?


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## ncerni (Aug 6, 2013)

Magnum9 said:


> So if I wanted to firm up the pro pedal on a 2011 RP2 with only the on/off switch, what would need to get changed?


There are few (2-4) very small (external diameter apprrox 2.5mm) shims under the spring of LSC(propedal) needle. You would have to add some shims or substitute them with a thicker shim.


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## Magnum9 (Jun 8, 2011)

Is it possible to remove the needle from the top without removing the nitrogen or losing any oil?


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## ncerni (Aug 6, 2013)

Magnum9 said:


> Is it possible to remove the needle from the top without removing the nitrogen or losing any oil?


Sorry, It's impossible.


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## ncerni (Aug 6, 2013)

*IFP pressure and boost valve tune*

As far as I know boost valve tune is a pressure in IFP chamber in psi. But according to that e-mail in 2008 fox increased pressure in IFP for non-boost valve shocks from 300 to 400 psi. I suppose they did it because shocks were sucking air into oil because of alternating load on o-rings when fully compressed (like hitting hard on jumps when flying too far or not far enough). Since all RPs are similar in construction (boost valve is only a part on shim stack) I suppose this problem may still occur on boost valve shocks. And they are loaded with only 200psi??

So if I inflate IFP chamber to 200psi boost valve will work fine for a month or two and then I will have air in oil. If I inflate it to 400psi compression damping will be too hard. So what can I do. (I suppose 200psi and service when I get air in oil)


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## tacubaya (Jan 27, 2006)

They raised to 400 because with 300 it would develop a slight "knock".


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## Thumpernut (Nov 10, 2013)

My 2009 RP2 has oil around the ProPedal lever, and the suspension is not firming up after I enable PP.

What symptoms would indicate that my RP2 IFP pressure was down? I'm hoping I can get away with a DIY air sleeve service and not have to send the whole shock in to the agent for a re-gassing of the IFP chamber. If the shock does need the IFP serviced, can anyone point me to some safe instructions (I'm handy with a lathe, etc)

Last year I sent it to the FOX agent in Cape Town, but I'd rather learn to do the whole service myself.

Thanks


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## NordieBoy (Sep 26, 2004)

I think my RP3 needs a service too.
Rebound damping is locked out or 1 click back has opened it too much.


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## ShirleySerious (Mar 8, 2013)

Thumpernut said:


> If the shock does need the IFP serviced, can anyone point me to some safe instructions


RP2 and RP3 factory service guide here.


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## christexan (Jun 1, 2004)

Someone posted a now-expired EBay link in this thread to an o-ring for the ProPedal seal. I did some web searching out of curiosity, and found this...
AS3.91x1.27-70N | Nitrile Metric O-ring 70 Durometer (Buna-n / NBR)
It matches their description, I don't know if it's RIGHT or not, but it matches what that previous poster found, if that previous "viton" post was correct (Back in 2012). 
Very cheap from this site.


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## ktm520 (Apr 21, 2004)

Magnum9 said:


> So if I wanted to firm up the pro pedal on a 2011 RP2 with only the on/off switch, what would need to get changed?





ncerni said:


> There are few (2-4) very small (external diameter apprrox 2.5mm) shims under the spring of LSC(propedal) needle. You would have to add some shims or substitute them with a thicker shim.


There are also two different springs that I have seen in the shocks I have rebuilt. I found a source online for the springs, but they weren't cheap in small quantities. They are .375" long x .12" od. The soft spring had .019" wire and stiffer was .026" wire. From memory, this was 24 and 41 lb/in for the spring rates. I found a washer perfect for the shims available at McMaster Carr but forgot the dimensions. If your interested, I can do some digging and find the spring source and shim dimensions.


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## kelstr (Jan 17, 2008)

Thumpernut said:


> My 2009 RP2 has oil around the ProPedal lever, and the suspension is not firming up after I enable PP.
> 
> What symptoms would indicate that my RP2 IFP pressure was down? I'm hoping I can get away with a DIY air sleeve service and not have to send the whole shock in to the agent for a re-gassing of the IFP chamber. If the shock does need the IFP serviced, can anyone point me to some safe instructions (I'm handy with a lathe, etc)
> 
> ...


All the Fox shocks I get with oil leaking out the adjuster lever need to be gone through, the seals on the shaft and needle get hard and leak and the shock looses oil and nitro pressure and must be O/H to bring it back to life .

Most of the time Fox uses proprietary sized "O" rings on the shaft and needle and I end up machining down the needle alittle to fit my bigger tighter seals and the things do not leak again.

Fox has changed to different seals many times on their shocks and the things will still leak .
You just gotta get in there and fix it :skep:

I can guaranty that last year when you sent it in it did not get the shaft and needle resealed ,........resealing the shaft and needle is not a quick job :eekster:


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## ncerni (Aug 6, 2013)

*Disassembly, reassembly and bleeding*

Someone might find this useful. I will later add more pics, more detailed information, etc, but now I am too lazy. You can comment on the link, and I will try to make it better.

https://************************/d/1...it?usp=sharing


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## Dougal (Jan 23, 2004)

ncerni said:


> Someone might find this useful. I will later add more pics, more detailed information, etc, but now I am too lazy. You can comment on the link, and I will try to make it better.
> 
> https://************************/d/1...it?usp=sharing


Die angeforderte Seite ist ungültig. 
The page you requested is invalid.


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## ncerni (Aug 6, 2013)

It doesn't allow me to share a link here. So if anyone needs advice servicing these shocks please PM me.


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## josemari220 (Nov 11, 2015)

*rp23 leak, valving assembly, stiff propedal mod*

I have just serviced my RP23. Oil leak by pro pedal lever area. It causes low oil level that causes ifp plate goes too high and shock bottom out with much less travel. It causes low ifp chamber pressure so Propedal doesn¨t work. A chain reaction. Change the micro o-ring that seals the propedal rod. I hate the needle inflate method. I´m planning to put a modified schrader valve to do it.

I show you my RP23 valving assembly. It could be usefull if you lost their position.








I also modify the stifest propedal position. If you put an small piece of wire into propedal inner comp rod, before the ProPedal plunger assembly tip. I put 2.7mm piece that avoid movement of propedal plunger in position 3. In position 1 and 2, propedal still works like standard. With this modification, the shock is not really locked, because, oir flows through speed valves, but the feeling is near locked out, and i can sprint, stand on pedals with almost no rear movement. I´m happy with it.


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## shubham (Sep 5, 2017)

thuren said:


> I made up a charge needle for my nitrogen tank. You basically loosen the nut a little to release pressure from the silicone/rubber disk, insert needle, pressurize, remove needle, tighten nut down, then leak check.
> 
> It's a little finicky be careful with the needle.
> Also, make sure you insert the needle dead center, as the hole on the backside of the disk is small.


Can you tell me how do you made up charge needle?


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## adyamg (Jan 19, 2017)

tacubaya said:


> They raised to 400 because with 300 it would develop a slight "knock".


I know this is old news ... and post but I am having a 2013 CTD EVO that is knocking.

It developed the knock in time.
I have done a damper service and found foamy aerated oil. Didn't find anything else suspect for the knock inside.
I have opened the damper after reading some posts that said that air(nitrogen) in damper oil could cause the knock. I have re-inflated the IFP to 300PSI with my shock pump but the knock is still present.

From what you are saying I might guess that the knock originated from IFP pressure going down as some of the nitrogen got mixed with the oil.
And now the knock might be still rpersent because I am not able to go over 300psi?!

If you are kind enough, could you elaborate more on how the knock "forms" as I havent heard this theory anywhere else and it seems somehow possible considering I didnt find any other cause.

Thanks!


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