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  1. #1
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    Fox CTD "O/C" Evolution damper service info and pics

    Just did a service on a CTD fork for the first time. This one has the CTD "O/C" damper which is the cheaper version than the FIT one, I gather. The Foxracingshox.com service site has info on bleeding the oil out of the trail adjust and remote lockout versions through the bleed port.

    The CTD O/C (Open Cartridge?) damper doesn't have any bleed port, and the compression adjustment shaft goes all the way through the damper unit, unlike the older FIT forks from which you could just remove the compression adjuster to bleed the damper.

    Don't do what I did and remove the circlip and spring from the top of the damper, it's very fiddly to get back on.

    Pull the damper head out of the cartridge using your 26mm socket, the thread is a standard thread unlike the Rockshox units:



    Once you've got the CTD adjust knob off the top you'll see a stack with a tiny circlip at the top, then a washer, then a spring, then a larger washer. Underneath this is the spring and ball for the CTD detents. There's no need to remove this assembly unless you need to replace the ball or spring.



    The bottom of the damper has a small bolt which holds on a wing-shaped plate that covers the ports for the C, T and D settings.

    Climb setting (small and large ports closed):



    Trail setting (small port closed, large port open):



    Descend seting (small and large ports open):



    If you remove the spring and circlip assembly from the top of the damper, the easiest way to get them back on is to undo this small bolt from the bottom (marking which way the wing plates are aligned on the 4-sided shaft), push the shaft up through the top, and reassemble without any need to compress the top spring while putting the circlip back on (a 4-handed operation).

    Refill the damper with 82.5cc of Fox red, test the CTD functions and reinstall.

    Drawings from Foxracingxhox:

    32 mm 29 120-130 FLOAT O/C CTD Cartridge Assembly

    32 mm 26/29 FLOAT O/C CTD Cartridge: Subassemblies

    Have fun everyone!

    - Joel
    Attached Thumbnails Attached Thumbnails Fox CTD "O/C" Evolution damper service info and pics-ctd-oc-1.jpg  

    Fox CTD "O/C" Evolution damper service info and pics-ctd-oc-2-descend.jpg  

    Fox CTD "O/C" Evolution damper service info and pics-ctd-oc-3-trail.jpg  

    Fox CTD "O/C" Evolution damper service info and pics-ctd-oc-4-climb.jpg  

    Fox CTD "O/C" Evolution damper service info and pics-ctd-oc-5-top.jpg  

    Cycling is Serious Business.

  2. #2
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    Man, thanks for sharing.

    Did you noticed if the compression and rebound pistons have shims?

    Thanks again!
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  3. #3
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    Hey Joel,

    Just came across your post, having started my own thread yesterday asking advice about changing the oil in this damper.

    Could you tell me how you drained the oil from the O/C damper, and how you refilled with new oil? Is it a 'sealed' unit like a FIT cartridge, or like the open bath dampers I'm familiar with?

    As you said, no instructions on the Fox web site for the O/C damper, so I'd kinda like to know what I'm getting myself in for before I dismantle this baby... Thanks.

  4. #4
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    Quote Originally Posted by Warp View Post
    Man, thanks for sharing.

    Did you noticed if the compression and rebound pistons have shims?

    Thanks again!
    You've probably found one by now, but just for completing the thread. There are shims on the comperssion damper, but how stiff they are I'm not entirely sure. The size of the ports suggest orifice choke damping.

    Rebound is not shimmed.

    Quote Originally Posted by PerthMTB View Post
    Hey Joel,

    Just came across your post, having started my own thread yesterday asking advice about changing the oil in this damper.

    Could you tell me how you drained the oil from the O/C damper, and how you refilled with new oil? Is it a 'sealed' unit like a FIT cartridge, or like the open bath dampers I'm familiar with?

    As you said, no instructions on the Fox web site for the O/C damper, so I'd kinda like to know what I'm getting myself in for before I dismantle this baby... Thanks.
    Just for the others who stumble across this thread:
    Think manitou TPC cartridge, but with bleed holes so if the damper is over-filled they spew the excess damper oil into the bushing lube oil. Test full stroke on the bench before putting the damper back in.
    Which explains why the oil you drain from the damper leg will always look mixed.
    There is a valve arrangement on these bleed ports. Presumably so the oil doesn't leak into the lower legs when the fork is inverted or lying flat.

    A clunky mid-stroke change in these forks means not enough oil or air in the oil. Air will obviously stroke it's way up and out but insufficient oil won't.
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  5. #5
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    Quote Originally Posted by Dougal View Post
    You've probably found one by now, but just for completing the thread. There are shims on the comperssion damper, but how stiff they are I'm not entirely sure. The size of the ports suggest orifice choke damping.

    Rebound is not shimmed.



    Just for the others who stumble across this thread:
    Think manitou TPC cartridge, but with bleed holes so if the damper is over-filled they spew the excess damper oil into the bushing lube oil. Test full stroke on the bench before putting the damper back in.
    Which explains why the oil you drain from the damper leg will always look mixed.
    There is a valve arrangement on these bleed ports. Presumably so the oil doesn't leak into the lower legs when the fork is inverted or lying flat.

    A clunky mid-stroke change in these forks means not enough oil or air in the oil. Air will obviously stroke it's way up and out but insufficient oil won't.
    Actually I don't think there are valves on the bleed holes. I know when I left mine upside down for 10 mins I lost damping in the first part of the stroke consistent with with a loss of damper oil. This wasn't a temporary loss of damping straight after being upside down. It was permanent until I next serviced it and replaced the oil.

    That was one of the many reasons why I sold it.

  6. #6
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    I hang mine upside down frequently and never have had an issue.

    The shim on the base valve is purely a hsc blowoff for Climb. It is preloaded with a stiff coil spring. Port orifices all around in this jewel. I have a '14 120. It spikes terribly in T and D is too soft for anything but a sunday drive.

  7. #7
    rgf
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    Quote Originally Posted by Dougal View Post
    Which explains why the oil you drain from the damper leg will always look mixed.
    There is a valve arrangement on these bleed ports. Presumably so the oil doesn't leak into the lower legs when the fork is inverted or lying flat.
    Hello, I have a float 32 o/c. Yesterday I did the second lower leg service of its life.
    The first time I was a bit puzzled to find the damper side oil kind of yellowish when I drained it but I just thought it was old, cleaned everything, put the correct Fox Green quantity and the fork worked fine.

    This time it was even more yellow, and I just serviced it three months ago. I did the usual lower leg (and air shaft) service, left the cartridge unchanged. The first strokes the damping was completely absent (C mode didn't lock it out at all), then it looks like it sucked some oil in and started working but it still doesn't lock out as before and even rebound isn't working properly.

    Is it really that normal to find mixed damping and lubrication oil in the right lower leg? Given that the fork has less than a year, should I send it for warranty?
    I thought I could threat this damper like a sealed cartridge and just change the lubrication oil but it looks like it's leaking the damping oil in the lower leg.
    Last edited by rgf; 07-23-2014 at 08:00 PM.

  8. #8
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    Quote Originally Posted by rgf View Post
    Hello, I have a float 32 o/c. Yesterday I did the second lower leg service of its life.
    The first time I was a bit puzzled to find the damper side oil kind of yellowish when I drained but I just thought it was old, cleaned everything, put the correct Fox Green quantity and the fork worked fine.

    This time it was even more yellow, and I just serviced it three months ago. I did the usual lower leg (and air shaft service), left the cartridge unchanged. The first strokes the damping was completely absent (C mode didn't lock it out at all), then it looks like it sucked some oil in and started working but it still doesn't lock out as before and even rebound isn't working properly.

    Is it really that normal to find mixed damping and lubrication oil in the right lower leg? Given that the fork has less than a year, should I send it for warranty?
    I thought I could threat this damper like a sealed cartridge and just change the lubrication oil but it looks like it's leaking the damping oil in the lower leg.
    I'd be tempted to try wrapping a road bike inner tube section around those bleed holes to keep the oil in the cartridge.

    I don't understand this design at all. I have no idea what they were thinking.
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  9. #9
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    Quote Originally Posted by rgf View Post
    Hello, I have a float 32 o/c. Yesterday I did the second lower leg service of its life.
    The first time I was a bit puzzled to find the damper side oil kind of yellowish when I drained it but I just thought it was old, cleaned everything, put the correct Fox Green quantity and the fork worked fine.

    This time it was even more yellow, and I just serviced it three months ago. I did the usual lower leg (and air shaft) service, left the cartridge unchanged. The first strokes the damping was completely absent (C mode didn't lock it out at all), then it looks like it sucked some oil in and started working but it still doesn't lock out as before and even rebound isn't working properly.

    Is it really that normal to find mixed damping and lubrication oil in the right lower leg? Given that the fork has less than a year, should I send it for warranty?
    I thought I could threat this damper like a sealed cartridge and just change the lubrication oil but it looks like it's leaking the damping oil in the lower leg.
    That's exactly what happened with mine. The lock out stopped working properly and the rebound became inconsistent. I was very disappointed with my evo fork.

  10. #10
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    Oil shouldn't leak out of the holes when inverted or during use. I'd be looking at the shaft seal if damper oil is getting in the bath oil.

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    Quote Originally Posted by ktm520 View Post
    Oil shouldn't leak out of the holes when inverted or during use. I'd be looking at the shaft seal if damper oil is getting in the bath oil.
    What is stopping the oil leaking out the holes when the fork is inverted?

  12. #12
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    An unsubstantiated theory. There are 4 small holes around the top of cartridge.

  13. #13
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    The first gen of these cartridges had no holes (as per the one in my pics from last year). I don't think they had the spring loaded pressure relief valve in the plastic base/rebound assembly either. As a result, when the pressure spiked they exploded! No surprises there. The circlip holding in the plastic base assembly was usually the thing to break apart.

    The second gen which were issued as warranty replacements had holes drilled in the top, 4 of them, about 2mm. I personally theorise that these were just returned cartridges which had been drilled and then sent back out to customers until a better solution could be engineered.

    The later ones I've seen have had no bleed holes in the top, but a spring and ball arrangement in the plastic base assembly which serves as a blow-off valve in case of spiking pressure.

    All in all, the cartridge design is pretty crappy, with the bladder-type FIT cartridges being a much better product.

    I've had Evolution cartridges which were overfilled from the factory, as and such the damper only got half travel, as well as some which were under filled giving no damping in the bottom part of the stroke.

    There is nothing stopping the oil leaking from the holes when the fork is inverted. If you do the drilling mod yourself to a cartridge which Fox won't warranty but which is leaking due to pressure, one or two smaller holes should suffice and will slow down the leaking.

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  14. #14
    rgf
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    Too bad I just sent it for a warranty service, now I'm curious which cartridge gen I had... let's hope they will just put a FIT cartridge there and ditch this crappy o/c one.
    I find it irritating that the cartridge needing to be serviced more often has little to none docs about it.

    Thinking about selling it when it gets back from service.

  15. #15
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    Re: Fox CTD "O/C" Evolution damper service info and pics

    Quote Originally Posted by tomacropod View Post
    All in all, the cartridge design is pretty crappy, with the bladder-type FIT cartridges being a much better product.
    I'll second that!

    My Evo came on a '14 Scott. It has the 4 holes up top, but I recall some type of check valve when I had it apart. It hangs upside down most of the time and has never lost oil.

  16. #16
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    Actually,the fork cartridge I posted pics of was from '13 MY bike.

  17. #17
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    Thanks for the clarification people. It seems that there's different versions of this cartridge. Mine was a 2014 fork on a giant trance. It definitely had no valves or anything to prevent oil leaking out the holes. Sounds like they've fixed this on some forks.

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    Can someone post a picture of the holes that you are talking about? I've got a Evo 26 150 2013 I'm about to service for the first time. Thanks for all the info.

  19. #19
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    They're nothing you need to consider in your servicing. Just remove the damper head as per the first pic. There may or may not be a couple of holes just below the bottom of the thread, above the damper head in the air space above the damper oil.

    Refill it with fox red when you go to reassemble it. Actually, it probably doesn't matter what oil you use in this crappy damper, it will still be crappy.

    - joel
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  20. #20
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    Serviced my Evo fork this weekend. Piece of cake thanks to Tomacropod's post. I took the dampener cartridge completely out as well as the air spring piston, then reassembled it using mobile 1 ATF in the OC, and mobile 1 5w30 in the lower legs. The fork in trail mode has a lot less compression dampening than before, which is what I was after. There's a lot less stiction overall too! I was blowing through travel with this setup, so I added 5ml of oil into the air chamber. Feels pretty decent, much better than the stock setup, but I need to get more time in the saddle. BTW, mine must be a later model fork, as it has the 4 holes drilled, and has a white plastic piece with 4 small check valves to keep cartridge fluid from leaking out. The fork is a factory spec off of a '13 Pivot Mach 5.7 that I bought (lightly) used.

  21. #21
    rgf
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    Quote Originally Posted by rgf View Post
    Thinking about selling it when it gets back from service.
    Hey guys, the fork (originally a float 32 evolution 150) came back from service with a new steerer and a FIT CTD with Trail Adjust cartridge. Now I'm not sure if I want to sell it anymore...

    I was looking at a 2014 Marzocchi 55 CR but reading the DBC cartridge description it sounds awfully similar to the O/C one. Hybrid between open bath and sealed cartridge, oil is dumped in the lowers in case of high pressure and sucked back in later... Do you guys have any insight about it? Would I be getting just a stiffer fork with a worse damper?

    Thanks and sorry for the OT!

  22. #22
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    Why not give it a try? I demoed a Yeti SB5 last weekend with a Fox 34 CTD FIT fork, and really liked it. Sweet bike too!

    Update on my Evo fork; in addition to the Mobile 1 fluids, I replaced the Fox Float fluid in the air chamber with Redline heavy shock proof gear oil. This stuff is so slippery that it is not recommended for synchronized gear boxes. I added an additional 10 cc to the chamber to get a little more support from mid stroke on. The fork rides so much better! Small bump compliance is excellent, and I'm not blowing through travel like I was before. If you don't mind tinkering, you can get these forks to work pretty well.

  23. #23
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    10cc is a lot, you'll see in your next service that the oil has migrated into the lowers.

  24. #24
    rgf
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    Quote Originally Posted by daytonadogie View Post
    Why not give it a try? I demoed a Yeti SB5 last weekend with a Fox 34 CTD FIT fork, and really liked it.
    I am, still not sure of the outcome though. Fit damper seems to work fine, you can appreciate both compression and rebound clicks effects on the ride.
    It just feels a lot sticky, especially on small bumps, I doubt it's from the damper, probably it's just dry or too much float fluid in the air chamber or both. Wouldn't be the first time I see a fork come back dry from Fox service...

    Could even be that they changed the bushings and needs to wear them a bit... too bad I have no way to know it since they don't give any report about what they actually did on the fork, I have to figure it out looking at it.

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    Hello, does have FLOAT EVOLUTION some air volume spacer under air volume cap? Something like this: http://fcdn.mtbr.com/attachments/sho...ke-air-cap.jpg

    It is too progressive for me even if I pump low pressure (SAG 25%)

  26. #26
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    No, mine didn't. Are you having problems getting full suspension travel? Most people are complaining that the CTD forks are too linear and not progressive enough, especially in the D mode.

  27. #27
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    Quote Originally Posted by MirosPikos View Post
    Hello, does have FLOAT EVOLUTION some air volume spacer under air volume cap? Something like this: http://fcdn.mtbr.com/attachments/sho...ke-air-cap.jpg

    It is too progressive for me even if I pump low pressure (SAG 25%)
    Mine has one. It is an OEM on a Giant.
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    When I compare Reba SL (2010) with this FLOAT EVOLUTION (140 mm 650B 2014), I cannot use full travel of the fork and it is much less sensitive. It's so horrible that I want to sell it (under price) and buy Suntour AURON.

    In addition, I have a problem with creaking in the crown. On Thuesday, it comes from service, so I will see.

    It is OEM from Canyon Spectral AL 6.0 (Germany).

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    well I hate to say this but I took my 2014 trek fuel ex 8 29er (w/ fox float 32 evolution CTD fork on it) for the first ride today and now cleaning the bike off at home I noticed the descend and trail mode settings on the fork seem to have lost the click that kept them in place before. its not like the switch moves around on its own now, which would be bad enough, but worse the trail mode feel doesn't appear any different than the descend mode. It is as if 95% of the switch travel (from descend to right before climb mode) is full open. You know, I almost don't want to care but wtf, I just bought this bike last week. I have read already at least one similar account of this failure.

    So when I go to trek store, should I ask for rebuild with FIT. Is the 2014 trek fuel ex8 29er equipped with this faulty O/C version? Thanks guys...

    wtf...should've stayed use. I like the bike otherwise but wtf...one ride...come on...I was on lighter trails too.

  30. #30
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    It could be oil level, it could be the little spring and cap holding the CTD valve against the piston. It could be a few other things too.

    The CTD 32 appears to be an even stranger design than the 34 EVO CTD. This one has a spring loaded ball valve in the cartridge lower seal head. So if pressures get too high (no idea what pressure that valve is set to) it drops oil out the bottom of the cartridge and into the lower leg.
    The one I saw last week had no oil left in the damper cart. 72cc had blown down into the lower leg and most of that went out past the wiper seals.

    At least with the EVO 34 CTD fork the oil holes are at the top so it can't lose ALL of it's oil.
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    Thanks Dougal. Interesting to know, and usually I am the DIY guy in the forums trying to work something out on my own or get input on a custom solution...but not today....today I am thinking how do I get this fixed without any cost or getting my hands dirty.

    I am guessing start at trek superstore I bought it from?

  32. #32
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    Quote Originally Posted by kevbeer View Post
    Thanks Dougal. Interesting to know, and usually I am the DIY guy in the forums trying to work something out on my own or get input on a custom solution...but not today....today I am thinking how do I get this fixed without any cost or getting my hands dirty.

    I am guessing start at trek superstore I bought it from?
    Yep I'd talk to the shop, they should deal with FOX (or Fox through trek) and sort you out.
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  33. #33
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    Quote Originally Posted by Dougal View Post
    It could be oil level, it could be the little spring and cap holding the CTD valve against the piston. It could be a few other things too.

    The CTD 32 appears to be an even stranger design than the 34 EVO CTD. This one has a spring loaded ball valve in the cartridge lower seal head. So if pressures get too high (no idea what pressure that valve is set to) it drops oil out the bottom of the cartridge and into the lower leg.
    The one I saw last week had no oil left in the damper cart. 72cc had blown down into the lower leg and most of that went out past the wiper seals.

    At least with the EVO 34 CTD fork the oil holes are at the top so it can't lose ALL of it's oil.
    The relief valve is at the top of the cartridge, not bottom. I can't see it blowing that much oil out of the top during operation, but maybe hung upside down. What about the shaft seal?

    On the 32 base valve, the outer cup is pressed on and holds the rotary valve against the piston. I've seen one come partially dislodged and you could push the adjuster knob down a couple mm's (remote style adjuster). I pressed it back on and it hasn't moved . . . yet.

  34. #34
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    Quote Originally Posted by ktm520 View Post
    The relief valve is at the top of the cartridge, not bottom. I can't see it blowing that much oil out of the top during operation, but maybe hung upside down. What about the shaft seal?
    I knew people wouldn't believe me. So I took photos.

    Fox CTD "O/C" Evolution damper service info and pics-img_3735.jpg

    That spring has a ball on top of it (cartridge side top of photo) which acts as a pressure relief and vents oil past the lower seals.

    The shaft seal looked fine, but was replaced anyway.

    The cap on the CTD valve had also come off inside this cartridge.
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  35. #35
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    Wow! Why??

    Its been 6 months since I had a 32 cartridge apart but don't remember it looking like that.

  36. #36
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    Quote Originally Posted by ktm520 View Post
    Wow! Why??

    Its been 6 months since I had a 32 cartridge apart but don't remember it looking like that.
    Your guess is as good as mine. It would be interesting to see what the opening pressure is. Especially to compare that with the pressures experienced with a heavy rider, high air pressure and rebound fully closed!

    I guess it ensures the damper side never runs out of bath oil!
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  37. #37
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    Does the 34 not have that relief valve in the seal head?

  38. #38
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    Quote Originally Posted by ktm520 View Post
    Does the 34 not have that relief valve in the seal head?
    The only 34 CTD I've been into had relief holes at the top of the cartridge. I don't recall any in the seal head, but I wasn't looking for it either. They still spill oil into the bath, but they don't spill all the oil.

    At least with the 34 you could possibly make it into a bladder with a section of road-bike inner tube. I had plans to do that as the rider kept heating the oil and blowing enough out the cartridge. But he gave up and sold the bike instead.
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  39. #39
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    I think this cartridge is one of the crappiest and cheapest things Fox has made, ever.

  40. #40
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    Quote Originally Posted by tacubaya View Post
    I think this cartridge is one of the crappiest and cheapest things Fox has made, ever.
    That is the main thing that comes out of this thread. Regarding the relief valves, I've seen them at the bottom, holes at the top, and nothing on the early ones. With a few revisions in a small time there are a heap out there that look different.

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  41. #41
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    Are there seal kits for this damper (Mine is the 2014 34 version)? Or is it not an end user thing? I see plenty of FIT kits, but not much for this. It might just be I'm blind. Was going to do the mid-winter new wipers/oil in lower and at least oil in damper, but wasn't sure if it's worth/needed to do the seals too?

    Thanks!

  42. #42
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    Shouldn't need new seals in the damper just new oil.

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    Quote Originally Posted by tomacropod View Post
    Shouldn't need new seals in the damper just new oil.

    - joel
    Thanks Joel.

  44. #44
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    Getting ready to do a service on one of these (2014 100mm travel CTD 29" O/C).

    Does it make sense to disassemble the fork, replace the wipers/seals, replace the open bath fluid, etc. before fiddling with filling the CTD damper with the red fluid by doing this:

    With the top cap of the damper removed, compress the fork so the cartridge tube extends up out of the crown (as shown in the OP), and then simply fill the damper cartridge by pouring the prescribed amount of red Fox fluid into the cartridge tube before re-installing the top CTD assembly?

    Is there going to be any purging necessary to get air out?

    Is there something I am missing here?

    Is it possible to put too much fluid into the damper assembly?

    What would be the result of having too much fluid, or not enough fluid?

    TIA

  45. #45
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    Quote Originally Posted by jeffj View Post
    Getting ready to do a service on one of these (2014 100mm travel CTD 29" O/C).

    Does it make sense to disassemble the fork, replace the wipers/seals, replace the open bath fluid, etc. before fiddling with filling the CTD damper with the red fluid by doing this:

    With the top cap of the damper removed, compress the fork so the cartridge tube extends up out of the crown (as shown in the OP), and then simply fill the damper cartridge by pouring the prescribed amount of red Fox fluid into the cartridge tube before re-installing the top CTD assembly?

    Is there going to be any purging necessary to get air out?

    Is there something I am missing here?

    Is it possible to put too much fluid into the damper assembly?

    What would be the result of having too much fluid, or not enough fluid?

    TIA
    It makes the most sense to strip the fork, remove the damper, drain oil, clean everything, then all back together with new oil.

    The oil volumes/heights for these CTD cartridges are critical. Too little and you hit the wall of oil part way into the stroke (feels awful). Too much and it'll dump oil into the lower legs.

    The oil volumes in the fox mega chart of doom are generally on the money. But it can be like deciphering code trying to find the right line in the charts.
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  46. #46
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    To the OP/Joel... What travel fork did you do this work on? You mention filling up the damper to 82.5cc. Because these dampers are "not serviceable", it's tough to find the volumes amounts for these dampers. I'm doing this work on a 130mm fork. Found one Fox page that stated a comparable fork with 130mm of travel would need 74.0cc. Would this make sense? Is the fork you did the work on a 150mm fork or something?

  47. #47
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    Poop, not sure of this fork but generally use oil height on these ones. Fill to about 10mm above the upper shim stack. I've found that reassembling with low air pressure, ie get the right height then compressing the damper rod about half way before screwing it down, helps a bit with the pressure spiking which kills these dampers.

    - joel

  48. #48
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    Poop,
    I serviced my 130 over the weekend and went with the 74.5 from the Fox chart.
    The fork is working great!

    Sent from my XT1254 using Tapatalk

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    Quote Originally Posted by tomacropod View Post
    Poop, not sure of this fork but generally use oil height on these ones. Fill to about 10mm above the upper shim stack. I've found that reassembling with low air pressure, ie get the right height then compressing the damper rod about half way before screwing it down, helps a bit with the pressure spiking which kills these dampers.

    - joel
    Quote Originally Posted by davez26 View Post
    Poop,
    I serviced my 130 over the weekend and went with the 74.5 from the Fox chart.
    The fork is working great!

    Sent from my XT1254 using Tapatalk
    Thanks a bunch for the info guys! Also just found out my fork was part of the recall so I'll be getting an "updated" damper. I think it's just an updated O/C damper but I'm crossing my fingers that they'll send me a FIT. Have to work with a local Fox authorized dealer. They're being super cool and letting me simply bring in the damper by itself instead of the entire shock. Good thing too because it's in pieces right now!

  50. #50
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    Fox CTD "O/C" Evolution damper service info and pics

    I serviced my Fork and damper over the weekend, and it turned out great.
    The fork had started getting a bit of movement in 'C', and just didn't feel the same. I saw the instructions here, and even called Fox. I am still not sure how I feel about that conversation, as they rightly pointed out that to service the damper, you have to visit the 2014 and up instructions listed here: http://www.ridefox.com/help.php?m=bike&id=460 . I asked about the seals to do this, and they kept balking even to the point of 'our guys don't like to open those up, and just swap them'. Just send me what I need. They sent a kit with the new top seals, and crush washers. Whatever.
    Anyway, I used the instructions here and the link, I didn't measure if the damper was low, but I did a drain and fill, and used the heights from the Service Center, Service Forks, Oil Volumes, #51: http://service.foxracingshox.com/consumers/index.htm .
    30cc per side, and 74 cc to damper. I did add an additional 2cc fluid to the air valve side, kinda acting like a volume reducer for my 235#.
    The forks feels 100% better. The fork is back to new, and I am happy. I am not in the know enough to really discuss the merits of whether this is a 'good' or 'junk' fork. I do know that I takes the edges off the trail, I get 95% of the travel, CTD definitely operating, it isn't overly hard or mushy, it just has a progressive feel that I like when I ride.



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    So i just got a hold of a 2013 evo. Since I have seen everywhere that the damper is pure crap, is the 2014 (maybe 2015 too?) year parts the only one I can change it out to?

  52. #52
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    Quote Originally Posted by Iranwithscissors View Post
    So i just got a hold of a 2013 evo. Since I have seen everywhere that the damper is pure crap, is the 2014 (maybe 2015 too?) year parts the only one I can change it out to?
    No. My Fox dealer got me a 2014 or a 2015 FIT damper to replace my 2013 Evo damper. Since you have a 2013, see if it's part of the recall. If it is, you can most likely upgrade to a FIT damper for a fraction of the cost. Cost me $130 to get a brand new FIT damper on my recalled 2013 Evo fork.

  53. #53
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    Quote Originally Posted by Poopshute View Post
    No. My Fox dealer got me a 2014 or a 2015 FIT damper to replace my 2013 Evo damper. Since you have a 2013, see if it's part of the recall. If it is, you can most likely upgrade to a FIT damper for a fraction of the cost. Cost me $130 to get a brand new FIT damper on my recalled 2013 Evo fork.
    Ya I'm hoping it falls in the recall. I'll be checking the serial number when I get off work today

  54. #54
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    Another addition to this thread.

    I've been given a 2013 O/C CTD, 100 mm travel, 32 mm stanchion Fox Float fork to look into what caused it to lose lockout (blue knob had no more effect). The fork has had no previous maintenance done on.

    The damper looks exactly like in the original post. No holes in body, black plastic compression piston. It measured 465 mm in fully extended length. There was dark red oil inside, with about 15 mm air gap to the bottom of compression piston. I have not noticed much redness in the color of damper side lower leg oil, it was dirty greenish. The damper has no visible damage to it.

    Perhaps there was not much oil to begin with and some of it eventually made its way out around damper rod/lower seal head sealing and into the lower leg. I filled the damper to 85 mm oil level (from top of black tube) with cheap hydraulic oil for cars, and the blue knob now has effect again.

    I also have found this Fox tech support article where they advice to (gasp!) physically destroy the old damper without holes in favor of a similar new unit that had the holes drilled.
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  55. #55
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    Quote Originally Posted by J. Random Psycho View Post
    Another addition to this thread.

    I've been given a 2013 O/C CTD, 100 mm travel, 32 mm stanchion Fox Float fork to look into what caused it to lose lockout (blue knob had no more effect). The fork has had no previous maintenance done on.

    The damper looks exactly like in the original post. No holes in body, black plastic compression piston. It measured 465 mm in fully extended length. There was dark red oil inside, with about 15 mm air gap to the bottom of compression piston. I have not noticed much redness in the color of damper side lower leg oil, it was dirty greenish. The damper has no visible damage to it.

    Perhaps there was not much oil to begin with and some of it eventually made its way out around damper rod/lower seal head sealing and into the lower leg. I filled the damper to 85 mm oil level (from top of black tube) with cheap hydraulic oil for cars, and the blue knob now has effect again.

    I also have found this Fox tech support article where they advice to (gasp!) physically destroy the old damper without holes in favor of a similar new unit that had the holes drilled.
    Hey man. There's a good chance that fork of yours was part of the recall. The recall will get you a new Evo damper swapped out free of charge. If you have an extra $120 or so, you can convince Fox to send you out a FIT cartridge damper. $120 for a brand new FIT damper is a sick deal. It's what I did recently with my 2013 Evo damper. Everyone I've talked told me how much better the FIT damper is compared to the Evo damper. Never even bothered to ride the fork with the Evo damper and opted to take the offer from Fox. To check if your fork is on the recall list, go here and enter in the serial number:

    Model Year 2013 Evolution Series Voluntary Recall | FOX

    I was bummed to hear about the recall at first but in the end, I ended up getting a $350+ damper for a fraction of the cost.

  56. #56
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    Thank you! I checked it and it said No Action Required. Looks like 100 mm travel models are not in the recall as it only applies to certain 120-160 mm forks.

  57. #57
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    Quote Originally Posted by J. Random Psycho View Post
    Thank you! I checked it and it said No Action Required. Looks like 100 mm travel models are not in the recall as it only applies to certain 120-160 mm forks.
    Bummer.

  58. #58
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    Does anyone know the oil wt and volume for a CTD Damper in a 2014 Talas 650B?

  59. #59
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    Quote Originally Posted by nowlan View Post
    Does anyone know the oil wt and volume for a CTD Damper in a 2014 Talas 650B?
    Oil weight is 47 cst @40c. Volume is usually around 82cc. the evo cartridges spill excess oil so that is easy. The fit cartridges are good with the bladder relaxed at ride height.
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    Quote Originally Posted by Dougal View Post
    Oil weight is 47 cst @40c. Volume is usually around 82cc. the evo cartridges spill excess oil so that is easy. The fit cartridges are good with the bladder relaxed at ride height.
    Do you have experience bleeding the CTD Damper side?

  61. #61
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    Quote Originally Posted by nowlan View Post
    Do you have experience bleeding the CTD Damper side?
    Yes. But are you talking CTD Evo or CTD FIT?

    The CTD Evo are simply add the amount of oil in the fox chart and screw it back together.

    The CTD FIT require a low pressure vacuum bleed/fill to get all the air out. But it can be done by hand with a reasonable result.
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    Quote Originally Posted by Dougal View Post
    Yes. But are you talking CTD Evo or CTD FIT?

    The CTD Evo are simply add the amount of oil in the fox chart and screw it back together.

    The CTD FIT require a low pressure vacuum bleed/fill to get all the air out. But it can be done by hand with a reasonable result.
    Mines the FIT

    Have you ever done it? what instructions did you follow, there is alot of conflicting diagrams/info on the net. If so, did you use the adapter tool?

  63. #63
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    Quote Originally Posted by nowlan View Post
    Mines the FIT

    Have you ever done it? what instructions did you follow, there is alot of conflicting diagrams/info on the net. If so, did you use the adapter tool?
    Yes I've done it. I made my own bleed fittings. It is a double start thread so not easy to make or use anything else.
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    Quote Originally Posted by Dougal View Post
    Yes I've done it. I made my own bleed fittings. It is a double start thread so not easy to make or use anything else.
    So once you have an adapter made, how do you draw the fluid into the damper?

  65. #65
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    Quote Originally Posted by nowlan View Post
    So once you have an adapter made, how do you draw the fluid into the damper?
    Gravity, vacuum and pressure.

    Mount the damper upright, for hand bleed use a syringe or funnel to hold a reservoir of fluid above which draws in oil and purges out air as you stroke the damper.
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    [QUOTE=Dougal;12682791]Gravity, vacuum and pressure.

    Mount the damper upright, for hand bleed use a syringe or funnel to hold a reservoir of fluid above which draws in oil and purges out air as you stroke the damper.[/QUOT

    Sounds like a lengthy process.

  67. #67
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    Quote Originally Posted by nowlan View Post
    Sounds like a lengthy process.
    It's always quicker to do a terrible job.

    Like using an impact driver on foot nuts..........
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    I just received a CTD Evo Fork with a situation I had not noticed or received before (and we´ve received CTD Evo cartridges which have literally been destroyed in use.)

    In this case the upper assembly of the compression unit is separated from the valve with the ports. It seems like the spring´s force separated the tube from the valve. The tube is still inside the valve but does not top out completely. This makes the cartridge compress about half an inch and then locks out in climb mode. The spring compresses under the fluid´s pressure, the tube tops out on the valve, and then in locks out like it should.

    Have any of you seen this in the past? I had not noticed it before in other EVO dampers? Is it normal?

    Just as extra info, this fork came out of a scott bike with the remote lockout for front and rear shocks. So the fork basically has open mode and climb mode.

    It seems to me that the tube is inserted in the valve from factory with an interference fit. However this tube does disassemble from the valve.

    Anyone got an idea of what could be going on here or if it´s normal?

    Fox CTD "O/C" Evolution damper service info and pics-img_7218-m.jpg

  69. #69
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    Quote Originally Posted by Josue View Post
    I just received a CTD Evo Fork with a situation I had not noticed or received before (and we´ve received CTD Evo cartridges which have literally been destroyed in use.)

    In this case the upper assembly of the compression unit is separated from the valve with the ports. It seems like the spring´s force separated the tube from the valve. The tube is still inside the valve but does not top out completely. This makes the cartridge compress about half an inch and then locks out in climb mode. The spring compresses under the fluid´s pressure, the tube tops out on the valve, and then in locks out like it should.

    Have any of you seen this in the past? I had not noticed it before in other EVO dampers? Is it normal?

    Just as extra info, this fork came out of a scott bike with the remote lockout for front and rear shocks. So the fork basically has open mode and climb mode.

    It seems to me that the tube is inserted in the valve from factory with an interference fit. However this tube does disassemble from the valve.

    Anyone got an idea of what could be going on here or if it´s normal?

    Click image for larger version. 

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    Yes I've seen that and fixed it. The shaft and piston were supposed to be a press fit. But the one I had was size for size with no interference fit.

    I peened the shaft and pressed it back together with Loctite. Problem solved. You will need to reclock the assembly at the top end to ensure the clicks line up with the ports.
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  70. #70
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    Quote Originally Posted by Dougal View Post
    Yes I've seen that and fixed it. The shaft and piston were supposed to be a press fit. But the one I had was size for size with no interference fit.

    I peened the shaft and pressed it back together with Loctite. Problem solved. You will need to reclock the assembly at the top end to ensure the clicks line up with the ports.
    Awesome!! Thankyou ver much, will do that. Did you use loctite 271 or 640?

  71. #71
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    Another question, what method did you use to peen the shaft?
    Thanks!

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    Quote Originally Posted by Josue View Post
    Another question, what method did you use to peen the shaft?
    Thanks!
    Centre-punch. I can't recall what loctite I used. The loctite doesn't matter as much as the peening.
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    Quote Originally Posted by Dougal View Post
    Centre-punch. I can't recall what loctite I used. The loctite doesn't matter as much as the peening.
    Thanks a lot!

  74. #74
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    Quote Originally Posted by Josue View Post
    Thanks a lot!
    Best way is to drill a couple of holes in two pieces of timber and hold the damper together in a vice. The holes avoid pressure on the adjuster rod and lower bolt. You'll need to make sure the ports and detents are aligned before pressing it back together again. Leave it clamped for a couple of hours. we use 641 loctite for this job.

    If you do enough evolution fork servicing, you'll keep a spare, repaired damper in stock to swap out so you can glue the original back together later.

    - Joel
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  75. #75
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    Quote Originally Posted by tomacropod View Post
    Best way is to drill a couple of holes in two pieces of timber and hold the damper together in a vice. The holes avoid pressure on the adjuster rod and lower bolt. You'll need to make sure the ports and detents are aligned before pressing it back together again. Leave it clamped for a couple of hours. we use 641 loctite for this job.

    If you do enough evolution fork servicing, you'll keep a spare, repaired damper in stock to swap out so you can glue the original back together later.

    - Joel
    Thanks Joel!

    I used 609 Loctite since I couldn´t get 641. (The numbers differ depending on the country).

    The damper has been fixed and is working properly now. I´ll post pictures ahead.

    Thanks,
    Josué

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    Quote Originally Posted by Dougal View Post
    Yes I've seen that and fixed it. The shaft and piston were supposed to be a press fit. But the one I had was size for size with no interference fit.

    I peened the shaft and pressed it back together with Loctite. Problem solved. You will need to reclock the assembly at the top end to ensure the clicks line up with the ports.
    Hi there, great thread for us evolution owners!
    I don't fully understand what you mean by "peen the shaft", are you using the punch down the shafts to flare it or slightly deforming it or something else?
    Thanks in advance.

  77. #77
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    Yeah, that´s what you have to do. I tried it on an evo damper a few weeks ago and it worked great. Just make sure you install the spacer in the rod before you flare it. Otherwise they may be difficult to reinstall.
    I increased the diameter 0.1mm............just checked my notes.
    Last edited by Josue; 08-03-2016 at 06:26 AM.

  78. #78
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    Quote Originally Posted by Betty_K View Post
    Hi there, great thread for us evolution owners!
    I don't fully understand what you mean by "peen the shaft", are you using the punch down the shafts to flare it or slightly deforming it or something else?
    Thanks in advance.
    Peening is dimpling the shaft with a centre-punch. This pushes up metal around the dimples to create an interference press-fit where there wasn't enough of one before hand.
    The loctite works in the remaining gaps to glue it together and ensure it stays together.
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  79. #79
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    Quote Originally Posted by Dougal View Post
    Peening is dimpling the shaft with a centre-punch. This pushes up metal around the dimples to create an interference press-fit where there wasn't enough of one before hand.
    The loctite works in the remaining gaps to glue it together and ensure it stays together.
    i picked up the 2015 evo oc 120 in december.
    i just had the tsb for wipers and gold fluid.
    no the trail and lockout come and go at will.
    when i got it back it did not work.
    after dropping all the psi and cycling it. it started working but lockout was mushy.

    now the fork is off the bike again and going back to tribikerun where it was serviced.

    i also noticed this fork developed a clunk on the damper side when in trail mode.

    im starting to hate this fork.

    drama queen device un worthy of being on my bike and shuts my riding down.

    its a 120 120 bike with a 70 ha.

    what fork should i use to replace it with?


    thanks

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    Hello,

    i just read all the information about the open cartridge - very interesting.
    At the moment i am doing the service on my Fox 34er 160 mm Talas 2014.

    Can someone tell me the correct volume of oil for die cartridge - unlikely there are NO information on the Fox Website......

    Or is it right just to fill the cartridge up to the top?

    i just got information regarding the 2013 (35,2 ml) model bute not the 2014 one....
    Fox 2013 34 TALAS 26" 160 FIT CTD - Oil Volumes - Bike Tech Tools

    Thanks

  81. #81
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    You can fill it aproximately 10mm above the shim stack.

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    Am i right that i dont have to bleed the open cartridge after refilling?

    Do you put the oil in when the piston rod is fully extended??

    by the way Fox Germany told me to put 87 ml in the 34 Talas with 160mm travel.......

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    Does anyone has the specification of the ctd unit?

    i need to know i which direction the shims are located.

    Can anyone help me?,


  84. #84
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    Quote Originally Posted by etg47 View Post
    Does anyone has the specification of the ctd unit?

    i need to know i which direction the shims are located.

    Can anyone help me?,

    The shims are on the shaft above the piston but below the spring.
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    Hello friends
    Thread really useful, we don't find much technical information in Spain, and on the Fox website they already imply that they don't want users to manipulate the latest products cartridge since 2014
    My experience,
    2011 Fox 120 Fit and RP23 smoothly, great product
    2013 Fork and Shox 120 CTD total disaster, extra cost in Fox service and solved with value custom tuned
    2015 Fork EVO 130 CTD remote, model 2014 and Shox CTD 120, and a few weeks ago, a "clunk" in Trail mode when rebound
    First thinking, why Fox again and not Rockshox?
    But in the end I decided to do some DIY, open Fork and damper CTD O/C
    The first strange thing is the green oil of the lower leg air spring was clean and bright, and the right lower leg a dirty green
    My CTD cartridge has holes in the top and small balls of the safety valves comented before, and its red oil looked dirty too
    While I get the Fox WT20 gold and service kit, I reassembled everything using for each bottle 30mm WT10 from Harley Davison, and on the CTD the same old fluid
    The noise has disappeared, and for now everything works ok
    The noise in Trail mode rebound, I think is not alarming, comes by returning the fluid down and pushing the valve group against the lower aluminum support

    It is only an impression, but I think this may be produced by an oil degradation or incorrect oil levels
    The problem is that this levels of the CTD OC 2014 has been impossible to locate in Fox, only here I found this information (72,5ml, 82ml o 10mm below) otherwise use the Fox 2013 models chart
    When I receive the service seals and the Gold and Red oil from Fox I will open the Fork again for the full service and make some photos to comment on how everything has gone
    Last edited by ppiyo; 05-21-2017 at 10:57 AM.

  86. #86
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    After getting some information from Fox service, it's clear this system CTD and specially EVO O/C series will be no longer avaialble ¿they assume a mistake with this product?
    The only solution is new FIT4
    Anyway, my fork works again smoothly and C, T, D clearly differenced with the original EVO cartridge repaired, while ordering the new FIT4
    One of the problems of this system, mine was this, is that the valve body drops out (probably not completely) from the axis, I think is fitted only by pressure
    Just clean it all and some glue (epoxy 2 components) during 24 hours
    At the same time, new seals and fluid (Red Fox is 10WT) You can test 7,5WT, 5WT, depend your weight, use, preferences...
    If you don't have remote control, be careful with valve body orientation, it must be aligned with upper head/aluminium axis to lock 3 positions (CTD) with the small ball and spring. No matter if you use remote control
    Some pictures with components and tools for repair, full service with ring seals, dust seals and oil
    The new dust seals 2016, add some extra difficulty in assembly than the previous ones if you do not have the appropriate tool
    Attached Thumbnails Attached Thumbnails Fox CTD "O/C" Evolution damper service info and pics-img_20170513_133340.jpg  

    Fox CTD "O/C" Evolution damper service info and pics-img_20170511_151835.jpg  

    Fox CTD "O/C" Evolution damper service info and pics-img_20170511_200428.jpg  

    Fox CTD "O/C" Evolution damper service info and pics-img_20170511_151835_1.jpg  

    Fox CTD "O/C" Evolution damper service info and pics-img_20170511_200255.jpg  


  87. #87
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    Quote Originally Posted by ppiyo View Post
    After getting some information from Fox service, it's clear this system CTD and specially EVO O/C series will be no longer avaialble ¿they assume a mistake with this product?
    The only solution is new FIT4
    Anyway, my fork works again smoothly and C, T, D clearly differenced with the original EVO cartridge repaired, while ordering the new FIT4
    One of the problems of this system, mine was this, is that the valve body drops out (probably not completely) from the axis, I think is fitted only by pressure
    Just clean it all and some glue (epoxy 2 components) during 24 hours
    At the same time, new seals and fluid (Red Fox is 10WT) You can test 7,5WT, 5WT, depend your weight, use, preferences...
    If you don't have remote control, be careful with valve body orientation, it must be aligned with upper head/aluminium axis to lock 3 positions (CTD) with the small ball and spring. No matter if you use remote control
    Some pictures with components and tools for repair, full service with ring seals, dust seals and oil
    The new dust seals 2016, add some extra difficulty in assembly than the previous ones if you do not have the appropriate tool
    Fit GRIP should also be available and cheaper than the FIT4. I have a 2017 Fox 34 with Fit GRIP and it performs just great. It also self bleeds which should make rebuilding much easier. No bladder to manually bleed.

  88. #88
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    You are right
    I will check if this grip is available for my 32/130/29
    Thanks