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  1. #1
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    Marzocchi 55 TST2 conversion to shim damping: step by step

    This is a modification to a Marzocchi 55 TST2 fork damper cartridge. This modification converts the lock-out to a low speed compression adjustment and adds a high-speed compression shim stack.

    (For a bleed only proceedure, see here: TST2 Bleed alternative w/pics )

    It all started with an MTBR post asking for help on how to set up a Mazocchi 55 TST2 fork...And turned into a complete damper modification.

    The problem I was having was high speed spiking. With the help of Flyag1 (he cracked open his damper cartridge and set me the pics) we were able to figure out that the damping was a port orifice design. The port orifice being the source of the high speed spiking. But from Flyag1's pics I also noticed something else; a blanked off potential compression piston.

    This compression piston was simply blanked off with just some thick washers. I speculated that we could replace the washers with a shim stack with the lock-out orifice acting as an adjustable bypass port. Sounds great, but modifying my new 3 year warranteed fork on some pics and guesswork was pretty racy for me. Then I got the dreaded hydro-locking damper cartridge - a week before Sea Otter (I was entered to race). And Marzocchi Tech Department replied to my post with confirmation of our guesses and additional great info, to give me the confidence I needed.

    I knew I had to crack open the cartridge to be able to run the fork for Sea Otter. I figured, if I'm in there I may as well give the damper mod a shot. I had my spacer ready, shims ready, beers ready...


    Here is how it went down:

    1) Pry up the lock out with a flat blade screw driver - it is held in by the friction of an O-ring.



    2) Remove the plastic bits and keep them in order



    3) Use a 22mm ground down socket and unscrew the top of the damping cartridge from the fork crown.

    This next part is NOT part of the Marzocchi recommended damper bleed proceedure - but I was able to do the whole modification and bleed without removing the damping cartridge.

    4) Push the fork to bottom (air and spring removed from spring side) while making sure that the damping cart is still extended out of the fork.

    5) Unscrew cart top. I used an old tube to friction hold the outside of the cart to keep it from spinning. It was tough and required a beer for courage. lol.

    6) After loosening carefully pull compression damper straight out.


    fixxxer0 provided a correction:
    its a 27mm socket you need to grind down, not a 22mm as stated in the picture below



    7) Remove bottom bolt from damper shaft. More beer for courage. Marzocchi Tech Department advised to heat the bolt as there is loc-tite on the threads - and I don't think I could have gotten the bolt off without doing so. Again, I used my old tube to hold the damper.



    8) Bye bye thick unflexing washers. Hello flexy goodness shims and spacer! Welcome speed sensitive damping!
    Right now it is a pyramid stack 17mm, 16mm, 16mm, 15mm, 13mm. All (I think) .010 thick except for the 13mm which is .005 thick. 18mm scraped the side of the cartridge. (all 8mm ID)

    The spacer is an aluminum chainring bolt spacer.




    9) Measure oil level in the damper at full extension. Flyag1 came up with measurement of 110mm from the top - it is dead-on! This will give an oil level just above the piston/shim for proper operation.

    10-x) Reverse rest of proceedure to put back together.

    Success = beer.


    RIDING RESULTS:

    Damping was controlled and felt as normal (pre-mod) with trail riding at wide-open. Then I stuffed the front wheel straight into the boneyards at speed; the smaller stuff was simply erased, 3" or larger squared rock stills had some feedback, but it was controlled and not spiked feedback (and could be related to spring ramp-up). It did make my rear shock seem less plush - not a technical issue just a feel issue. End of DH rock run, my hands were not killing me as they were prior to the mod. I did still have some arm pump, but that is expected on that particular trail.

    Drops and jumps seemed to go just a bit deeper into travel, (spring rate or less HSC?) but the ramp up of the air spring still gave that lovely landing-on-a-couch feel, and covered any mistakes.

    Lock-out is now a compression adjustment. Full lock out is firm compression (port orifice is off and piston/shim is active) that makes the fork only move about an inch under stand and pedal situations (2 inches max when stand and mash is tired and sloppy). The cool part this this retains 80% of the lock out benefits, but the travel remains well controlled and active - still eating up small and large features. I will never have to worry if I am locked or not on a downhill, as it is still perfectly rideable on "full lock".

    So am I happy? Hell yes! It is now the fork I thought I bought and wanted. I love that I can also easily modify to shim stack to shape the compression to my riding.

    I am using a quarter turn compression setting to give an nice controlled and efficient feel on XCish and flowy trails - it also helps with dive. (just a quarter turn gives me full shim stack only compression)

    MAINTENANCE RESULTS:

    After a couple of 20+ mile rides, 40-50 runs on the Sea Otter dual slalom course that included uncountable jumps and drops all is working fine (it should). And I am glad to say the damper has not hydro-locked. I should also note it only takes about 10-15 minutes to get to shim stack now.

    Start modding!!

    Thanks again to Flyag1 and Marzocchi Tech Department. They helped me to make a good fork great.

    P
    Last edited by All Mountain; 09-25-2008 at 03:18 AM.

  2. #2
    "El Whatever"
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    AM, please stick it or add it to the Service thread!!!

    Would ya, mate??

    P... Great post and mod.
    Check my Site

  3. #3
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    WTF is Zoke thinking putting the thick washers in there and not just shipping the fork with shims in the first freaking place!!!!!!!!!!!!!!!!!!!!!!????????????????
    My video techniques can be found in this thread.

  4. #4
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    Quote Originally Posted by Warp
    AM, please stick it or add it to the Service thread!!!

    Would ya, mate??

    P... Great post and mod.
    Done. It's in the Marzocchi Service Info Thread, accessible through the Fork and Shock service Information Sticky thread at the top.


    This thread indicates what we all suspected for the last few years.... that Marzocchi designers are not the sharpest tools in the shed.

  5. #5
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    Hey Pat, nice work. Did you have to mod the spacer at all? Did you loctite the bottom nut back on? Any side view pics post mod, prior to reassembly? Thanks again, if I can get my ata cart sorted I will def be doing the conversion!!! Cheers, Steve

  6. #6
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    Quote Originally Posted by Stevo the Devo
    Hey Pat, nice work. Did you have to mod the spacer at all? Did you loctite the bottom nut back on? Any side view pics post mod, prior to reassembly? Thanks again, if I can get my ata cart sorted I will def be doing the conversion!!! Cheers, Steve
    Thanks Steve, no mods done to the spacer it had an ID of 8mm and a thickness of 3mm. NO additional loctite added (seemed tight enough and I want easier access)

    Here is a pic of the compression part of the damper that Flyag1 took. Note that this was from the previous thread when we were figuring things out and "Lock out blow off" is not correct.

    P
    Attached Images Attached Images
    Last edited by Mr.P; 05-09-2008 at 07:48 AM.

  7. #7
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    nice job dude!!!

  8. #8
    "El Whatever"
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    Quote Originally Posted by All Mountain
    This thread indicates what we all suspected for the last few years.... that Marzocchi designers are not the sharpest tools in the shed.
    I don't think the problem lies in their designers.

    Shims cost more than regular washers. For us it's a few dollars, but for them could be thousands. And they can't let their cheapo model to have better damping than their top of the line. Money rules here.
    Check my Site

  9. #9
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    By chance does anyone know if a similar mod could be done to the TST2 on the previous AM line of forks??

    Thanks...

  10. #10
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    Quote Originally Posted by stiingya
    By chance does anyone know if a similar mod could be done to the TST2 on the previous AM line of forks??

    Thanks...
    If they're the closed cartridge type (not bladder), yes. Most probably.
    Check my Site

  11. #11
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    Quote Originally Posted by tscheezy
    WTF is Zoke thinking putting the thick washers in there and not just shipping the fork with shims in the first freaking place!!!!!!!!!!!!!!!!!!!!!!????????????????
    I think it was a marketing decision to put the washers in there. Perhaps they thought the lock out is what the market wanted, and the lock out requires blanking off the piston with the washers. (LO was kinda cool for stand and mash/hammer)

    And they can't have TST2 outperform TST Micro.

    It would be the same manufacturing process and cost of shims is cents.

    P

  12. #12
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    Cool, hell it may even outperform RC2/3 due to the shimmed piston. It just shows you how much marzocchi has sacrificed in recent times. They *should* have a shimmed piston with both compression and rebound shims, maybe adjustable low-speed compression and rebound bleed. It's utterly rediculous to have a ported damper when performance can be so much better.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

    You're turning black metallic.

  13. #13
    MK_
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    Nice work, man.

    _MK

  14. #14
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    Quote Originally Posted by All Mountain
    This thread indicates what we all suspected for the last few years.... that Marzocchi designers are not the sharpest tools in the shed.
    If we weren't very sharp then we wouldn't have been able to supply this info to Mr. P. in the first place.

    All Mountain you have now gotten under my skin. ...and this just makes it harder for me to come here and help out....but what should I expect right???

    At least I have unsharpened tools in my shed....and I'm not one.

    FYI, TST2 was and is designed to be a climbing feature nothing else. If you want a tuned compression you should buck up and get the TST micro. It has all the performance you get from this mod and more.
    Last edited by Marzocchi Tech Department; 05-28-2008 at 09:57 AM.
    Ride Your Bike!

  15. #15
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    Quote Originally Posted by Marzocchi Tech Department
    If we weren't very sharp then we wouldn't have been able to supply this info to Mr. P. in the first place.

    All Mountain you have now gotten under my skin. ...and this just makes it harder for me to come here and help out....but what should I expect right???

    At least I have unsharpened tools in my shed....and I not one.

    FYI, TST2 was and is designed to be a climbing feature nothing else. If you want a tuned compression you should buck up and get the TST micro. It has all the performance you get from this mod and more.
    So the TST Micro has compression shims in it?

    The reason I say this is that I had an AM1 with the TST 5, it included an orofice damper (the TST adjuster) and some sort of stiff-blow off, but no shims covering an orofice to react to impacts of varying force. I retrofitted a Z150 HSCV cart into it, which was a far superior ride in terms of suspension. I HIGHLY doubt that a TST Micro fork would be superior to this mod if it is anything like my TST5 damper. The AM1 tended to spike a lot over high frequency/fast impact bumps. This mod would give it a damper that's capable of dealing with low and high speed impacts with out that negative harshness that is caused by the orofice damper.
    Last edited by Jayem; 05-09-2008 at 10:12 AM.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

    You're turning black metallic.

  16. #16
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    Quote Originally Posted by Marzocchi Tech Department
    If we weren't very sharp then we wouldn't have been able to supply this info to Mr. P. in the first place.

    All Mountain you have now gotten under my skin. ...and this just makes it harder for me to come here and help out....but what should I expect right???

    At least I have unsharpened tools in my shed....and I not one.

    FYI, TST2 was and is designed to be a climbing feature nothing else. If you want a tuned compression you should buck up and get the TST micro. It has all the performance you get from this mod and more.

    Very, very tasteful.

  17. #17
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    Quote Originally Posted by MaddSquirrel
    Very, very tasteful.
    What ever. He's human, not some PR robot.

    I will take answers to questions regardless if he gets rightfully pissy about people stabbing him with worthless insults.

    I think we can all be happy the TST 2 is even user tunable to begin with.

  18. #18
    BC
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    Quote Originally Posted by Mr.P
    This is a modification to a Marzocchi 55 TST2 fork damper cartridge. This modification converts the lock-out to a low speed compression adjustment and adds a high-speed compression shim stack.

    (For a bleed only proceedure, see here: TST2 Bleed alternative w/pics )

    It all started with an MTBR post asking for help on how to set up a Mazocchi 55 TST2 fork...And turned into a complete damper modification.

    The problem I was having was high speed spiking. With the help of Flyag1 (he cracked open his damper cartridge and set me the pics) we were able to figure out that the damping was a port orifice design. The port orifice being the source of the high speed spiking. But from Flyag1's pics I also noticed something else; a blanked off potential compression piston.

    This compression piston was simply blanked off with just some thick washers. I speculated that we could replace the washers with a shim stack with the lock-out orifice acting as an adjustable bypass port. Sounds great, but modifying my new 3 year warranteed fork on some pics and guesswork was pretty racy for me. Then I got the dreaded hydro-locking damper cartridge - a week before Sea Otter (I was entered to race). And Marzocchi Tech Department replied to my post with confirmation of our guesses and additional great info, to give me the confidence I needed.

    I knew I had to crack open the cartridge to be able to run the fork for Sea Otter. I figured, if I'm in there I may as well give the damper mod a shot. I had my spacer ready, shims ready, beers ready...


    Here is how it went down:

    1) Pry up the lock out with a flat blade screw driver - it is held in by the friction of an O-ring.



    2) Remove the plastic bits and keep them in order



    3) Use a 22mm ground down socket and unscrew the top of the damping cartridge from the fork crown.

    This next part is NOT part of the Marzocchi recommended damper bleed proceedure - but I was able to do the whole modification and bleed without removing the damping cartridge.

    4) Push the fork to bottom (air and spring removed from spring side) while making sure that the damping cart is still extended out of the fork.

    5) Unscrew cart top. I used an old tube to friction hold the outside of the cart to keep it from spinning. It was tough and required a beer for courage. lol.

    6) After loosening carefully pull compression damper straight out.




    7) Remove bottom bolt from damper shaft. More beer for courage. Marzocchi Tech Department advised to heat the bolt as there is loc-tite on the threads - and I don't think I could have gotten the bolt off without doing so. Again, I used my old tube to hold the damper.



    8) Bye bye thick unflexing washers. Hello flexy goodness shims and spacer! Welcome speed sensitive damping!
    Right now it is a pyramid stack 17mm, 16mm, 16mm, 15mm, 13mm. All (I think) .010 thick except for the 13mm which is .005 thick. 18mm scraped the side of the cartridge. (all 8mm ID)

    The spacer is an aluminum chainring bolt spacer.




    9) Measure oil level in the damper at full extension. Flyag1 came up with measurement of 110mm from the top - it is dead-on! This will give an oil level just above the piston/shim for proper operation.

    10-x) Reverse rest of proceedure to put back together.

    Success = beer.


    RIDING RESULTS:

    Damping was controlled and felt as normal (pre-mod) with trail riding at wide-open. Then I stuffed the front wheel straight into the boneyards at speed; the smaller stuff was simply erased, 3" or larger squared rock stills had some feedback, but it was controlled and not spiked feedback (and could be related to spring ramp-up). It did make my rear shock seem less plush - not a technical issue just a feel issue. End of DH rock run, my hands were not killing me as they were prior to the mod. I did still have some arm pump, but that is expected on that particular trail.

    Drops and jumps seemed to go just a bit deeper into travel, (spring rate or less HSC?) but the ramp up of the air spring still gave that lovely landing-on-a-couch feel, and covered any mistakes.

    Lock-out is now a compression adjustment. Full lock out is firm compression (port orifice is off and piston/shim is active) that makes the fork only move about an inch under stand and pedal situations (2 inches max when stand and mash is tired and sloppy). The cool part this this retains 80% of the lock out benefits, but the travel remains well controlled and active - still eating up small and large features. I will never have to worry if I am locked or not on a downhill, as it is still perfectly rideable on "full lock".

    So am I happy? Hell yes! It is now the fork I thought I bought and wanted. I love that I can also easily modify to shim stack to shape the compression to my riding.

    I am using a quarter turn compression setting to give an nice controlled and efficient feel on XCish and flowy trails - it also helps with dive. (just a quarter turn gives me full shim stack only compression)

    MAINTENANCE RESULTS:

    After a couple of 20+ mile rides, 40-50 runs on the Sea Otter dual slalom course that included uncountable jumps and drops all is working fine (it should). And I am glad to say the damper has not hydro-locked. I should also note it only takes about 10-15 minutes to get to shim stack now.

    Start modding!!

    Thanks again to Flyag1 and Marzocchi Tech Department. They helped me to make a good fork great.

    P
    Wow, great post.
    I found basically the same thing with the ROCO TST coil. Way overdamped and slow for me. I had to remove 3 comp. shims. and 2 rebound shims to get a faster response. I guess it's difficult to design a damping system from riders 120 - 240#'s.

  19. #19
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    Sweet valley high! OK where did you get the shims and how much do you weigh? Did Tom help you size the shims?

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    damn!

    Dude, where did you find the shims? Do you know if this will work with an 07 All Mountain 1 TST2 cart? I find the TST lockout to be redundant when ETA is available on the other leg. I was thinking of replacing the TST2 with an RC2, but this sounds a lot cheaper (provided it would work).

  21. #21
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    Quote Originally Posted by thebronze
    Did Tom help you size the shims?
    Thats what he said:
    Here's what can be done. I did it and like it too but you loose the lock-out and turn it into a ripping performance setting. You will need 3 shims @ 18mm x 0.15mm thick with an 8mm ID hole. You will also need 3 washers 11mm OD by 11 ID. They need to be about 1mm thick.... Warning, if you break it you will pay for a new one.

    I would also like to know if this is also possible on All mountain with TST2. In one topic Tom said that it doesn't have bladder.

  22. #22
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    Quote Originally Posted by dougbot
    Dude, where did you find the shims? Do you know if this will work with an 07 All Mountain 1 TST2 cart? I find the TST lockout to be redundant when ETA is available on the other leg. I was thinking of replacing the TST2 with an RC2, but this sounds a lot cheaper (provided it would work).
    Shims can be had here:
    http://www.mx-tech.com/?id=products&subcat=153

    Or pilfered from Manitou forks.

    The pyramid shaped shim stack (large to smaller) is to create progressive damping. Less low speed, more high speed. Shims all the same size would create more low speed damping and less high speed.

    There is no real right or wrong way to set up the shim stack (within reason) - it is more of what is best for you and how you ride.

    P

  23. #23
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    Do you know if this will work on the 2007 AM 1 with TST2?

  24. #24
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    Why does a 55 need a lockout for climbing?

  25. #25
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    The tst2 cartridge looks a lot like the ETA setup on my Z1. Does anyone know if they are similar inside and if you can even get the ETA cart apart? I need to take mine apart as the rod unthreads from the piston occasionally.

  26. #26
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    Quote Originally Posted by thebronze
    Sweet valley high! OK where did you get the shims and how much do you weigh? Did Tom help you size the shims?
    I had some shims from a previous Manitou TPC project and from MXTech.com

    Tom was a huge help in giving us the ID and max OD of the shims. See here: http://forums.mtbr.com/shocks-suspension/marzocchi-55-tst2-set-up-help-needed-393052.html#post4289055 I went with a pyramid stack for a good balance of low speed and high speed compression in the shim stack.

    You can shape the stack to your needs. That is the beauty of this mod - improving your fork goes way beyond turning a knob. It is like doing what PUSH does (only without the dyno )

    What I was trying to achieve was allowing the orifice damper to still handle 50-75% of the duty, but when needed the shims would open removing any spike. The goal was to have a "platform" at what used to be lock-out (as mentioned above I did like the LO for fast climbing). This is why there are the number of shims I put in there. I might have put only 3 if I were to use the shims only for damping.

    I weigh 180.

    I just did another mod which is spring related that really opened up the small bump compliance. (I will post to another thread in a couple of days)

    P

  27. #27
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    Allright, Excellent...Now all we need is for you to package all the parts up for us in a kit.

  28. #28
    cgd
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    can someone please tell me in laymans terms what these shims do and how they do it?

  29. #29
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    Quote Originally Posted by cgd
    can someone please tell me in laymans terms what these shims do and how they do it?
    When you have a suspension damper, you have to be able to change the amount of fluid that can flow through the piston. This is usually done with shims on any quality type of damper, whether it be car, motorcross, or mountain bike. The shims are a stack of very thin flat washers that are stacked, and they usually constitute a "pyramid" shape of concentrically smaller or larger sizes. This essentially constitutes a "spring", and then during fast shock-shaft speeds the shims flex and open up, allowing a lot of oil to pass through.

    This is typically encountered at medium to higher speeds over a variety of sizes of bumps, and what the "high speed compression" term refers to is the speed of the shock shaft, not the bike, but usually the bike has to be moving at a fair clip to enter into this speed range. This is typically a difficult thing to adjust with an external adjuster, and when it is adjusted with an external adjuster it is often adjusting the "preload" or pressure on the shims, which increases or decreases that "spring" effect, although this doesn't really address the real advantage of shims, which is the ability to rearrange the shim stack to suit the rider, as the external adjuster just doesn't have the number of possibilities that the shim stack does. This rearranging of the shim stack (different size shims or less or more shims) is primarily what companies like "Push" do and other Mx tuning companies. There's a LOT more that Push can do, but the arrangent of the shim-stack to the rider is one of the primary things. There are a lot of forks with "compression" adjustments out there, but few of them actually adjust this aspect of the compression action. Other types of high-speed compresion dampers typically include lower-cost orofice-systems that sometimes incorperate a coil spring or other type of blow-off. The primary limitation here is that even though there's a "blow off" or way to pass more fluid, it doesn't constitute a linear change from the low-speed to high-speed circut and it's limited by the orofice size. At higher speeds these systems tend to "spike" and the fluid can't be passed fast enough through the fork. These types of system are characteristic of lower-cost dampers, such as the cheaper marzocchis. Recently, Marzocchi has been outfitting more and more forks with these types of systems, and even though they are a bit more complex than I just explained, they are still limited by the same things and the performance is nowhere near a good shimmed damper IMO (such as a current fox fork). As an example, the older rockshox boxxer forks (1998) had a lower-cost orofice damper system, and much later on I bought a handmade marzocchi super T from 1998 (very rare fork). The super T had a type of shimmed-damper with twin cartridges, and it was amazing how something produced in the same year when mountain bike suspension wasn't very advanced was so hands-down better. The marzocchi sucked up terrain and bumps in a way that blew my mind, compared to the rockshox. What is ironic though is that now rockshox is making good complex shimmed-dampers with their "speedstack/mission control" dampers, while marzocchi is going back to the more crappy stuff with some of their products. The thing is that you can't tell the difference between these two types of systems by just pushing down on the forks. An older shimmed-damper marzocchi super-T felt just as plush on the showroom floor as the much cheaper and simpler marzocchi Jr-T. Both forks looked almost identical, and felt identical at lower speeds.


    Low speed impacts are generally low-shaft speeds, resulting from certain kinds of bumps obviously, or drops, or jumps, these are typically low-shaft speeds comparitively. This type of damping is usually controlled by an orofice that allows fluid to pass and sometimes there is an adjuster that controls the amount of fluid that can pass through. When incorperated with yet another type of "blowoff", this can constitute damping typically referred to as "propedal" or "platform". Typically most compression adjusters affect some aspect of this low-shaft speed damping, although the fork has to be designed correctly with the proper relationship of high-speed shims, orofice sizes, and adjustments. As an example, marzocchi experiemented with a compression adjustment back in 2000, but it didn't pass enough fluid through and tended to "spike" as the fluid couldn't be passed through fast enough.

    I hope that was simple enough and explains why people are interested in this mod. Even the much more "high end" TST5 damper I had in my All-Mountain 1 in 2005 was not much more than an orofice damper. There was the bladder that the fluid passed between, but it came down to an orofice and not shim-controll. This is why I doubt that even the higher end "TST Micro" damper would perform as well as a good shimmed damper. It seems the entire idea of the "TST" stuff is to give the ability to lockout and adjust the compression damping, but the actual damper performance isn't all that great. At lower and even middle speeds it can seem to be fine, but at higher speeds mine would get harsh and spike some. You have two options, either live with the spiking or go with a bigger orofice that provides less damping control. If you happen to ride always in a certain speed range (lets say fairly slow without very big bumps) these traits described above are things that you may not notice much, in fact any time there's something better out there we tend to not really find any fault with our current stuff, even if the new stuff does perform better. But also keep in my what I said in my first paragraph, virtually every quality damping system out there uses shims to meter the amount of fluid that is passed, and you'll get much more consistant performance with that kind of set up and it will be able to perform consistantly in a wide range of trail conditions/types/speeds.
    Last edited by Jayem; 05-10-2008 at 08:58 PM.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

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  30. #30
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    many thanks for the depth of your response, i was only ever aware that compression damping was controlled by orofice systems. how ignorant!

    thanks again.

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    ... and if we just ... completed damper mod on xc600 tst2

    Ok, so after 2 failed attempts (not enough beer?) I have managed to complete the shim stack conversion on my 08 xc600. MrP did a great job on the pics and procedure, so I won't go over these details, but will add my 2c worth to give a bit broader experience.

    I have had hydro-lock as well as a few failed attempts at removing the bottom nut, so have to say opening the damper cart is easy as. Don't be scared! I had a lot of trouble removing the bottom nut due to an excess of loctite; in the end, what worked for me was clamping the damper shaft in a vice (with 2 layers of tube for protection), and then using more old tube in the familiar strapping wrench arrangement. Although the bottom of the shaft is hollow, the top has the comp adjuster rod running through it, so crush potential is pretty limited. I put a soldering iron into the nut to help soften the loctite (remember to remove the o-ring first, or you'll melt it).

    The loctite was red, which didn't give way with a "crack" like blue does, but was more like chewing gum. Consistent pressure applied here was what finally did it, rather than trying to crack the nut open. Patience is definitely required, as is a good 10mm socket.

    Thought I'd try a shim arrangement half way between Tom's and Pat's, so I went with
    3x (17mm x 0.1mm)
    2x (16mm x 0.15mm)
    1x (14mm x 0.1mm)
    1x (12mm x 2mm) filed down chainring bolt spacer

    This gave almost the exact same thickness as the original washer arrangement. I did apply a small amout of loctite blue just to make sure things don't come undone unless I want them to. Put it back together, ready to go!!

    Quick ride impressions (tooling around at the football field);

    With damper full open the fork was very plush, possibly more than before (no spiking?). I have become used to doing all my riding with the fork open (my bar mounted lockout broke on the third ride and I didn't like it anyway); the difference was subtle, but noticeable.

    With the damper fully closed, I at first wasn't sure if there was any difference (had I stuffed it up?) but on closer examination found that brake dive and bob were about half what they had been previously. The nice thing was that the fork doesn't feel stiff or unresponsive at all with this setting, still supple and compliant without the usual downsides. Will take it for a proper ride tomorrow to get a better idea, but so far I am impressed with the changes.

    I may mod the stack again to get more slow speed damping if I find it needed after a few rides (remove the 14mm, add another 16mm) but the beauty is that I can now do this easily and quickly if reqd.

    Huge thanks to MrP and Marzocchi Tech Dept for their invaluable help, I am a very happy vegemite indeed! Get modding!
    Cheers, Steve

    PS does anyone know if I can get the fork-mounted lever to retrofit instead of the remote?

  32. #32
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    Quote Originally Posted by Stevo the Devo
    Ok, so after 2 failed attempts (not enough beer?) I have managed to complete the shim stack conversion on my 08 xc600.
    Nice one!

    Yep, it's a bit scary trying to get the bottom damper nut off, but, IMHO, absolutely worth it.

    I would love to hear a ride report and how your shim stack feel is.

    I now run mine with compression at about half, which is giving me a very active yet still controlled stroke.

    P

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    Quote Originally Posted by Stevo the Devo

    I have had hydro-lock as well as a few failed attempts at removing the bottom nut, so have to say opening the damper cart is easy as. Don't be scared! I had a lot of trouble removing the bottom nut due to an excess of loctite; in the end, what worked for me was clamping the damper shaft in a vice (with 2 layers of tube for protection), and then using more old tube in the familiar strapping wrench arrangement. Although the bottom of the shaft is hollow, the top has the comp adjuster rod running through it, so crush potential is pretty limited. I put a soldering iron into the nut to help soften the loctite (remember to remove the o-ring first, or you'll melt it).

    The loctite was red, which didn't give way with a "crack" like blue does, but was more like chewing gum. Consistent pressure applied here was what finally did it, rather than trying to crack the nut open. Patience is definitely required, as is a good 10mm socket.

    just FYI from my sailboat rigging experiences... red loctite, when heated to i think around 300F(+/-), gives off a gas vapor you can see and usually hear.... its pretty sudden when youve hit the temp mark. ive used a propane torch before, but again this was on sailboat rigging - don't know how practical it is on a shock with possibly rubber gaskets and o-rings that might be too close for the heat.

    once the gas/hiss happens, bolts come right off no problems... theres no inbetween from what ive seen with red, either reach the right temp or struggle lol

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    Hi All,
    Have done a second shim mod, am now running 2x18.1, 1x14.1, 2x16.1, 2x14.1, 2mm spacer. This is much better than my original stack as it has more of a platform feel to it when the orifice is closed, without really losing the HS sensitivity. Will prob try different oil weight (slightly heavier) next mod to get better rebound control (it is still a bit fast) and a touch more LS damping, and will fit enduro seals at same time, but all is good. My fork now rides as well as pretty much anything I've ridden; this mod is very highly recommended!!

  35. #35
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    Just to follow up after 3 months: the mod just plain works and I'm lovin' it.

    80% of the lockout benefits with much better high speed damping.

    This fork has seen the podium twice, one of them the Downieville Downhill which sees speeds up to 40mph, and has high Sierra rock gardens galore. So I think it's workin'

    Stevo: thanks for the heads up on the platform-like shim stack. I am going to try that when it is time for a new fork for my SS.

    P

  36. #36
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    Quote Originally Posted by Mr.P
    Just to follow up after 3 months: the mod just plain works and I'm lovin' it.

    80% of the lockout benefits with much better high speed damping.

    This fork has seen the podium twice, one of them the Downieville Downhill which sees speeds up to 40mph, and has high Sierra rock gardens galore. So I think it's workin'

    Stevo: thanks for the heads up on the platform-like shim stack. I am going to try that when it is time for a new fork for my SS.

    P
    Thanks for the update!
    Jenson USA is closing the 55tst2 out for $325.00.

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    I've used boiling water before to soften up red locktite. Used to replace rubber u-joints on windsurfing equipment and boiling is safer on the rubber parts than a torch, heat gun, or soldering iron. It doesn't actually melt the locktite but does soften it up enough to get the parts loose.

  38. #38
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    Quote Originally Posted by WaveDude
    I've used boiling water before to soften up red locktite. Used to replace rubber u-joints on windsurfing equipment and boiling is safer on the rubber parts than a torch, heat gun, or soldering iron. It doesn't actually melt the locktite but does soften it up enough to get the parts loose.
    That's a good tip. I have read that because red loctite is actually a mechanical bond that if you don't release it properly (ie. proper heat) that metal will actually be removed and it can damage threads.

    Fixxer0 is right on about what happens when you heat red loctite to the proper temp. It vaporizes and you are supposed to be able to smell it. Then it no longer is bonding the parts.

    I read a tip of using a soldering iron to heat the area. It is more precise than than a torch.

  39. #39
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    Quote Originally Posted by wormvine
    That's a good tip. I have read that because red loctite is actually a mechanical bond that if you don't release it properly (ie. proper heat) that metal will actually be removed and it can damage threads.

    Fixxer0 is right on about what happens when you heat red loctite to the proper temp. It vaporizes and you are supposed to be able to smell it. Then it no longer is bonding the parts.

    I read a tip of using a soldering iron to heat the area. It is more precise than than a torch.
    You guys rock with all these tips!

    P

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    Update to XC600 shim modification

    Hi all,
    Just another quick follow up on the progress of this mod on the xc600 tst2. Firstly, I have realised that for this fork the correct oil height is 80mm from the top of the cartridge, not 110mm as per the 55's. Have also changed my shim stack for the (hopefully) last time; it is now 2x 18.1, 1x 12.1, 1x 16.1, 1x 14.1, 1x 13.1, 12mm spacer. I have also slightly increased the oil weight (by about 7%); am running redline 80% medium/20% light. This is a nice setup for me, with better LS damping even in the open position, still very responsive to HS impacts, and the "platform" shim keeps it very supple when the damper is closed. Best mod ever! Thanks heaps, Mr. P, you rock...

  41. #41
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    Great post!.! Thanks for the advice.
    Leave no bolt untuned!

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    I just got back to Texas from a week of riding some pretty gnarly stuff in Colorado and realized that I'm not getting the final 1.5" - 2" of travel on my TST2!!! Would performing this shim mod to my fork resolve this problem in addition to improving the high speed spiking? Or do I need to replace the cartridge as well? Thanks!

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    Quote Originally Posted by mrknocke
    I just got back to Texas from a week of riding some pretty gnarly stuff in Colorado and realized that I'm not getting the final 1.5" - 2" of travel on my TST2!!! Would performing this shim mod to my fork resolve this problem in addition to improving the high speed spiking? Or do I need to replace the cartridge as well? Thanks!

    I called up Marz with the same problem, they gave me an RMA # and said they know about the issue and recently redesigned the TST2 cartridge to fix the problem...

    doubt the mod alone will permanently fix your travel problems though

  44. #44
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    Quote Originally Posted by mrknocke
    I just got back to Texas from a week of riding some pretty gnarly stuff in Colorado and realized that I'm not getting the final 1.5" - 2" of travel on my TST2!!! Would performing this shim mod to my fork resolve this problem in addition to improving the high speed spiking? Or do I need to replace the cartridge as well? Thanks!
    The mod is primarily designed to reduce HS spiking and give a more controlled damping throughout the adjustment range; I very highly recommend it to enhance your fork's performance, provided you can get the parts and are reasonably mechanically savvy. The lack of travel could well be hyrdo-lock caused by too much oil in the damper. I did the bleed procedure on my tst2 (at the start of the shim-stack mod) refilled the lowers to the correct (updated) oil levels and so far have not had it re-occur in about 5 months; others have done the bleed and had the hydrolock recur soon after. You could give this a quick go, but if it happens again send the fork to Marz for the re-designed tst cart. I would suggest doing this before you do the mod, as it will technically void your warranty. Hope this helps. Cheers, Steve

  45. #45
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    For the last 2 days I have been reading every TST2 mod/thread I can find in preparation for this mod. So far I can follow the mod and blieve I'm going to go for it but am having trouble with shim stack/sizing.

    I have seen everything from 3x18, a 17-13 pyramid, and one alternating 14,16 etc..
    Can somepne simply explain the rhyme or reason for the different stacks, or how to stack them for a particular feel?
    Just because I'm green on it I'm tempted to go 3x18 but would like to understand how to stack for sifferent feels..

    Thanks for all the info!

  46. #46
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    Quote Originally Posted by theFuzz
    For the last 2 days I have been reading every TST2 mod/thread I can find in preparation for this mod. So far I can follow the mod and blieve I'm going to go for it but am having trouble with shim stack/sizing.

    I have seen everything from 3x18, a 17-13 pyramid, and one alternating 14,16 etc..
    Can somepne simply explain the rhyme or reason for the different stacks, or how to stack them for a particular feel?
    Just because I'm green on it I'm tempted to go 3x18 but would like to understand how to stack for sifferent feels..

    Thanks for all the info!
    Very briefly, thicker shims are stiffer and less reactive. Bigger initial shims (especially if thicker), give more LS damping and a more locked out feel; when the shims do open, they open up completely and give little further damping. A pyramid stack gives a more progressive feel to the damping, so after the shims deflect they still provide a degree of damping based on their circumference (bigger = more damping). A double pyramid or transitional arrangement is a bit like combining the two; opens up wide initially, but then gets support from the second pyramid below. Its a bit of trial and error and personal preference, so don't be afraid to try something, and then change it if you want; once you have done the conversion, changing the stack shape is quick and easy. Whichever way you go it will be vastly superior to the stock arrangement. Cheers, Steve

  47. #47
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    Quote Originally Posted by theFuzz

    I have seen everything from 3x18, a 17-13 pyramid, and one alternating 14,16 etc..
    Can somepne simply explain the rhyme or reason for the different stacks, or how to stack them for a particular feel?
    Just because I'm green on it I'm tempted to go 3x18 but would like to understand how to stack for sifferent feels..

    Thanks for all the info!
    If Steve's reply doesnt help, just let us know what you are after and maybe we can suggest something. Also, check out the TPC+ shim discussion by Reno, some good info there. After monkeying with that tpc+ a nice simple tpc style marzocchi would be a relief. Steve and Mr.p have done the mod so they could probably help you narrow it down. Are you after more low speed or high speed compression?

    I almost bought one of these forks just to do the mod but the travel adjuster scared me away. I'm glad I went Magura.

  48. #48
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    Quote Originally Posted by thebronze
    If Steve's reply doesnt help, just let us know what you are after and maybe we can suggest something. Also, check out the TPC+ shim discussion by Reno, some good info there. After monkeying with that tpc+ a nice simple tpc style marzocchi would be a relief. Steve and Mr.p have done the mod so they could probably help you narrow it down. Are you after more low speed or high speed compression?

    I almost bought one of these forks just to do the mod but the travel adjuster scared me away. I'm glad I went Magura.
    Hey Bronze, The travel adjuster works great if you perform a very simple, quick fix that Renegade posted to stop it winding down. It is actually a purely mechanical system that doesn't change performance in any way except travel; I like it a lot. Maybe not too late to grab that second fork... Cheers, Steve

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    Hey Fuzz,

    Here is some info that really helped me from Dougal's website (he posts here from time to time)

    Note the "Shim Stack Dampers" section
    http://users.actrix.co.nz/dougal.ellen/tuning.html

    Source website:
    http://www.dougal.co.nz/

    I also read a Dougal post from the TPC+ thread where he mentioned reducing the HSC shims for fast rock gardens... hmmm. I think I might try that.

    I am now riding more with my freebleed completely off and letting the shim stack to all the work. So far this is giving me a very controlled but adaptable stroke.

    P

  50. #50
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    I have the desire to make the mod not so much to get a particular feel but to take advantage of adjustable compression with shimmed valving.
    The fork seems to get ripped alot for not having this already but from my perspective its great that the you have the options to create these custom shim stacks.
    Most likely will ride it and break-in for a few weeks and then determine what features I would like work on...

    Thanks for the help, this will push the bike over the top...

  51. #51
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    This is a modification to a Marzocchi 55 TST2 fork damper cartridge. This modification converts the lock-out to a low speed compression adjustment and adds a high-speed compression shim stack.

    (For a bleed only proceedure, see here: TST2 Bleed alternative w/pics )

    It all started with an MTBR post asking for help on how to set up a Mazocchi 55 TST2 fork...And turned into a complete damper modification.

    The problem I was having was high speed spiking. With the help of Flyag1 (he cracked open his damper cartridge and set me the pics) we were able to figure out that the damping was a port orifice design. The port orifice being the source of the high speed spiking. But from Flyag1's pics I also noticed something else; a blanked off potential compression piston.

    This compression piston was simply blanked off with just some thick washers. I speculated that we could replace the washers with a shim stack with the lock-out orifice acting as an adjustable bypass port. Sounds great, but modifying my new 3 year warranteed fork on some pics and guesswork was pretty racy for me. Then I got the dreaded hydro-locking damper cartridge - a week before Sea Otter (I was entered to race). And Marzocchi Tech Department replied to my post with confirmation of our guesses and additional great info, to give me the confidence I needed.

    I knew I had to crack open the cartridge to be able to run the fork for Sea Otter. I figured, if I'm in there I may as well give the damper mod a shot. I had my spacer ready, shims ready, beers ready...


    Here is how it went down:

    1) Pry up the lock out with a flat blade screw driver - it is held in by the friction of an O-ring.



    2) Remove the plastic bits and keep them in order



    3) Use a 22mm ground down socket and unscrew the top of the damping cartridge from the fork crown.

    This next part is NOT part of the Marzocchi recommended damper bleed proceedure - but I was able to do the whole modification and bleed without removing the damping cartridge.

    4) Push the fork to bottom (air and spring removed from spring side) while making sure that the damping cart is still extended out of the fork.

    5) Unscrew cart top. I used an old tube to friction hold the outside of the cart to keep it from spinning. It was tough and required a beer for courage. lol.

    6) After loosening carefully pull compression damper straight out.


    fixxxer0 provided a correction:
    its a 27mm socket you need to grind down, not a 22mm as stated in the picture below



    7) Remove bottom bolt from damper shaft. More beer for courage. Marzocchi Tech Department advised to heat the bolt as there is loc-tite on the threads - and I don't think I could have gotten the bolt off without doing so. Again, I used my old tube to hold the damper.



    8) Bye bye thick unflexing washers. Hello flexy goodness shims and spacer! Welcome speed sensitive damping!
    Right now it is a pyramid stack 17mm, 16mm, 16mm, 15mm, 13mm. All (I think) .010 thick except for the 13mm which is .005 thick. 18mm scraped the side of the cartridge. (all 8mm ID)

    The spacer is an aluminum chainring bolt spacer.




    9) Measure oil level in the damper at full extension. Flyag1 came up with measurement of 110mm from the top - it is dead-on! This will give an oil level just above the piston/shim for proper operation.

    10-x) Reverse rest of proceedure to put back together.

    Success = beer.


    RIDING RESULTS:

    Damping was controlled and felt as normal (pre-mod) with trail riding at wide-open. Then I stuffed the front wheel straight into the boneyards at speed; the smaller stuff was simply erased, 3" or larger squared rock stills had some feedback, but it was controlled and not spiked feedback (and could be related to spring ramp-up). It did make my rear shock seem less plush - not a technical issue just a feel issue. End of DH rock run, my hands were not killing me as they were prior to the mod. I did still have some arm pump, but that is expected on that particular trail.

    Drops and jumps seemed to go just a bit deeper into travel, (spring rate or less HSC?) but the ramp up of the air spring still gave that lovely landing-on-a-couch feel, and covered any mistakes.

    Lock-out is now a compression adjustment. Full lock out is firm compression (port orifice is off and piston/shim is active) that makes the fork only move about an inch under stand and pedal situations (2 inches max when stand and mash is tired and sloppy). The cool part this this retains 80% of the lock out benefits, but the travel remains well controlled and active - still eating up small and large features. I will never have to worry if I am locked or not on a downhill, as it is still perfectly rideable on "full lock".

    So am I happy? Hell yes! It is now the fork I thought I bought and wanted. I love that I can also easily modify to shim stack to shape the compression to my riding.

    I am using a quarter turn compression setting to give an nice controlled and efficient feel on XCish and flowy trails - it also helps with dive. (just a quarter turn gives me full shim stack only compression)

    MAINTENANCE RESULTS:

    After a couple of 20+ mile rides, 40-50 runs on the Sea Otter dual slalom course that included uncountable jumps and drops all is working fine (it should). And I am glad to say the damper has not hydro-locked. I should also note it only takes about 10-15 minutes to get to shim stack now.

    Start modding!!

    Thanks again to Flyag1 and Marzocchi Tech Department. They helped me to make a good fork great.

    P

  52. #52
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    Quote Originally Posted by Stevo the Devo
    Hey Bronze, The travel adjuster works great if you perform a very simple, quick fix that Renegade posted to stop it winding down. It is actually a purely mechanical system that doesn't change performance in any way except travel; I like it a lot. Maybe not too late to grab that second fork... Cheers, Steve
    Cool, do you know what forks this damper is in? The ATA is a bit too much fork. I was looking at the Marzocchi XC 600 '08 at Jenson. The travel adjuster fix, is that for ATA2?

  53. #53
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    Quote Originally Posted by thebronze
    Cool, do you know what forks this damper is in? The ATA is a bit too much fork. I was looking at the Marzocchi XC 600 '08 at Jenson. The travel adjuster fix, is that for ATA2?
    The fix works for ata or ata2 forks so take your pick!

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    A few update as I finished the mod last night.

    1. You do not need a strap wrench to open the TST cartridge. Remove the cartridge and you'll find wrench flats on the bottom of the cart. You can then put your socket on top and your box wrench(13mm?) to crack it open.
    2. Same goes for the piston. I believe it was a 10 or12mm but keep the socket on the top and wrench on the bottom and it will come loose. I did not need to heat anything up to break the loctite.
    3. The 17mm OD shim is a bit too small and leaves the ports exposed. This will create more free bleed and less LSC. I recommend an 18mm OD shim #1.
    4. The xc600 TST2 can be upgraded to 140mm travel by removing a 20mm spacer below the spring on the pumping rod.

    I have not had a chance to ride it but i'm really excited to rip into it.

  55. #55
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    Quote Originally Posted by thebronze
    A few update as I finished the mod last night.

    ...

    I have not had a chance to ride it but i'm really excited to rip into it.
    Nice one! Thanks for the tips.

    Let us know how it rides.

    P

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    I should be getting my 55 tst2 tomorrow. After dumping over $500 on a Fox fork and still wanting the Marzocchi feel my old fork had, I couldn't resist $250.

    I have a question for the few of you who have experience with this mod. Will this shim-stack mod prevent the hydro-locking issue these forks are known for?

    I would like to just buy anything I need now and get the fork reliable before it goes on the bike. Then maybe some tuning here and there.

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    Good stuff!!!!

    After reading thought this thread I must say the 55 TST2 fork looks like it can be a very inviting. These can be found pretty darn cheap and once you get rid of the washers and add the shim stack you will have a decent performing fork without spending a fortune. Once the mod is done, (I'm thinking this was metioned) the damper is works exactly like the the TPC which we all know is a very reliable and well performing damper.

    I also like the fact that a RC3 cartridge could be installed at a later time.

    I'm looking for a replacement for my 06 Vanilla RC2. I'm looking for more bottom out control and with the air preload I think it would help.

    I have a few questions.

    This may be silly, but does this fork have adjustable rebound? I could find anything in this thread that mentioned it. If it doesn't have an adjustable rebound, can the rebound pistion be shimmed?
    Last edited by spacoli; 01-17-2009 at 04:56 PM.
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  58. #58
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    Quote Originally Posted by cesper
    I should be getting my 55 tst2 tomorrow. After dumping over $500 on a Fox fork and still wanting the Marzocchi feel my old fork had, I couldn't resist $250.

    I have a question for the few of you who have experience with this mod. Will this shim-stack mod prevent the hydro-locking issue these forks are known for?

    I would like to just buy anything I need now and get the fork reliable before it goes on the bike. Then maybe some tuning here and there.
    Hey Cesper,
    Unfortunately the mod will not fix the hydro-lock problem, it can only be fixed by replacing the damper (or at least the bottom end cap) with the newer design. I would recommend contacting marz USA (or Marz Tech Dept on these forums) to arrange for a replacement under warranty before you do the mod. Cheers, Steve

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    Hey spacoli, it does have adjustable rebound.

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    Good Call, Steve-O. I think I'm just gonna get the parts from Marzocchi and do everything at once. I know that if I put the fork on now, I'll just keep saying "one more ride" until it's too late.

    I'm really hoping I can get this thing to feel like my '04 Z1. Man, I should never have sold that thing

  61. #61
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    Quote Originally Posted by cesper
    I'm really hoping I can get this thing to feel like my '04 Z1. Man, I should never have sold that thing
    I still have one, mint condition, qr axle though. I'm hoping for the same results. Can anyone compare the two?
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  62. #62
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    Quote Originally Posted by Stevo the Devo
    Hey spacoli, it does have adjustable rebound.
    Nice, thanks Steve. Hey I have been reading some of your posts, looks like you have a handle on this stuff. Can the rebound piston be tuned with shims?
    Last edited by spacoli; 01-17-2009 at 07:30 PM.
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    Quote Originally Posted by spacoli
    Nice, thanks Steve. Hey I have been reading some of your posts, looks like you have a handle on this stuff. Can the rebound piston be tuned with shims?
    Hey Spacoli,
    Firstly, I won't claim to be any suspension guru, I know quite a bit about this particular mod, but past that I won't vouch for me! I do, however, have reasonably good mechanical aptitude and comprehension.
    Ok, so with the disclaimer out of the way, here are my thoughts. I don't think it would be easy to effectively shim the rebound circuit. I pulled it out to have a look (I have a spare damper with the dud bottom nut); it is, as you'd expect, basically a needle valve which varies the orifice size of a moving damper unit( it moves up and down in the cartridge) . There is a piston, but it has a check plate on one side and the other side is open (ports uncovered). The ports are also recessed on the uncovered side. In order for this piston to not affect compression damping as well, the ports need to allow for unhindered flow of oil on the compression stroke; in this direction the lightly sprung check plate permits oil to flow through the ports as well as the central orifice.
    Upon rebound, the check plate closes and the oil is forced to return through the orifice alone, so it's size totally controls the rate of rebound. In order to shim the rebound circuit, you would have to use shims that only partially covered the ports so as to still allow compression of the fork, you would also have to use a smaller check plate so that some oil passed through the ports on rebound (otherwise the shims won't do anything). All of this is going to seriously mess with the effect of the rebound adjuster (as the orifice will only be partially responsible for rebound behaviour. I'm not saying it can't be done, but I think it would involve a lot of trial and error to get a setup that still allowed unrestricted compression whilst allowing both the shims and the adjuster knob to have a significant effect. After all, you still want to be able to externally adjust rebound (at least to some extent) after the mod.
    So that's my take on it. I will no doubt consider this possibility further as it would be nice to be able to tinker with rebound as well as compression, But in the mean time I reckon just stick with the existing mod; it is simple, effective, and gives lots of tuneability.
    FWIW, I would be keen to hear other peoples thoughts on this matter (MrP? Derby? Jayem? Bueller?)
    Cheers,
    Steve
    Last edited by Stevo the Devo; 01-17-2009 at 08:40 PM.

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    So it's not a shimmed rebound piston.

    If this is the right picture, any shims would need added under nut. But looking at the piston there is no way it would work, this is only a one way piston. It would need to be like the Manitou two way flow rebound piston in the picture. There is three nice tapered ports for the oil to flow through and the check valve on the backside. It would be nice if the Manitou piston could be used.

    Just wondering, what is the O.D. and the I.D. of the marz piston?

    You could probably get another compression piston from Marz, flip it over, shim it and use it for the rebound side.

    Heck that's the only "tuning" Push offers on there Rockshox mods. They replace the stock rebound piston with their "two stage" shimmed piston. That just goes to show you rebound must be an important part of suspension tuning.

    Edit: I looked through the pictures in this thread again and found the compression pistion. It is only a two port not three like Manitou, but it would work on the rebound side if the I.D. bolt hole is the same and the thread depth on the rebound rod is long enough to get the nut plus shims.
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    Last edited by spacoli; 01-17-2009 at 09:27 PM.
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    Steve, Since you have an extra damper, when you get a chance, can you see if the compresion piston can be installed on the rebound rod? Thanks
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    Quote Originally Posted by spacoli
    Steve, Since you have an extra damper, when you get a chance, can you see if the compresion piston can be installed on the rebound rod? Thanks
    Since the mod has a TPC type damping, it would be worth studying how the Manitou TPC shimmed rebound works. TPC is based on pushing oil - how it is pushed and if it includes the rebound piston would be key questions, I think.

    It does appear that, if sizes match up, the compression piston could work on the rebound side.

    P

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    Quote Originally Posted by Mr.P
    Since the mod has a TPC type damping, it would be worth studying how the Manitou TPC shimmed rebound works. TPC is based on pushing oil - how it is pushed and if it includes the rebound piston would be key questions, I think.

    It does appear that, if sizes match up, the compression piston could work on the rebound side.

    P
    Hey guys,
    Will check the fit in the next day,or so and let you know. In terms of rebound tuning, I'm not quite sure how the shims work; for compression, the amount of force and speed varies due to terrain, but the rebound force would seem to me to be a relative constant ie the spring force. With an air spring it will be stronger at full compression, meaning the end-stroke rebound will tend to be slightly faster, which is the opposite of what you want, but I can't figure out how the shim stack could be made to work harder (slower rebound) with a higher force and less (faster) with a lighter force. Any ideas?
    The other option is to see if the rebound side of the compression piston could be altered, but again I don't see how this could yield the desired effect, and it would be unaffected by the rebound adjuster, thereby reducing its practicality. Hmmm, now I'm intrigued...

  68. #68
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    Quote Originally Posted by Stevo the Devo
    Hey guys,
    Will check the fit in the next day,or so and let you know. In terms of rebound tuning, I'm not quite sure how the shims work; for compression, the amount of force and speed varies due to terrain, but the rebound force would seem to me to be a relative constant ie the spring force. With an air spring it will be stronger at full compression, meaning the end-stroke rebound will tend to be slightly faster, which is the opposite of what you want, but I can't figure out how the shim stack could be made to work harder (slower rebound) with a higher force and less (faster) with a lighter force. Any ideas?
    The other option is to see if the rebound side of the compression piston could be altered, but again I don't see how this could yield the desired effect, and it would be unaffected by the rebound adjuster, thereby reducing its practicality. Hmmm, now I'm intrigued...
    I'm no expert, but I would think it would be more controled and consistant with the shims. I thought that was the idea with a shim stack depending on the stack arangement. It would be just the opposite as is. there is a fixed piston that only lets so much oil pass through. The shims would bend and allow the oil to pass with the increase rebound speed at full compression.

    This maybe why Push does a two stage rebound? I know when I had my DHXC Pushed the rebound felt way slow. They told me not to worry, it's because of the two stage rebound, they explain why but I can't remember. The shock feels great to ride.
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  69. #69
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    Quote Originally Posted by spacoli
    I'm no expert, but I would think it would be more controled and consistant with the shims....

    I know when I had my DHXC Pushed the rebound felt way slow. They told me not to worry, it's because of the two stage rebound, they explain why but I can't remember. The shock feels great to ride.
    A rebound shim stack would allow you to run a slower free bleed rebound which would open up on bigger hits (more spring). This creates a more controlled and wider range of damping than an orifice damper.

    P

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    Quote Originally Posted by Mr.P
    A rebound shim stack would allow you to run a slower free bleed rebound which would open up on bigger hits (more spring). This creates a more controlled and wider range of damping than an orifice damper.

    P
    Yeah thats what I thought, but I don't get why it's better. It would mean that on smaller stutter bumps the shock will be more likely to pack up (due to the slower free bleed), but on bigger hits it will be more likely to buck (due to the shims opening). Seems to me that whilst a shimmed piston is preferable for compression damping, the rebound damping requirement is best suited by the orifice damper curve (less damping at low speed/spring pressures and more at high speed/spring pressures). I think this is where position sensitive damping is better that speed sensitive.
    Now opening the topic up for anyone to shoot holes in my logic...
    Cheers, Steve
    Last edited by Stevo the Devo; 01-18-2009 at 10:17 PM.

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    Quote Originally Posted by Stevo the Devo
    Now opening the ropic up for anyone to shoot holes in my logic...
    Cheers, Steve
    YOur logic is correct. Or at least I agree with it.

    But you can get similar results with a shim stack and zero bleed. I'm a fan of zero bleed. Meter all the flow, control it to the last bit. Separate compression from rebound.
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    Quote Originally Posted by Warp
    YOur logic is correct. Or at least I agree with it.

    But you can get similar results with a shim stack and zero bleed. I'm a fan of zero bleed. Meter all the flow, control it to the last bit. Separate compression from rebound.
    Hey Warp,
    Thanks for chiming in, much appreciated. I agree that, like church and state (couldn't resist the analogy) rebound and compression are best kept separate.
    The good thing is that in this cartridge (TST2) they are already separate; the passive damper in the top of the cartridge does all the comp damping (and maybe a tiny bit of rebound) whilst the piston on the rebound rod does all the rebound damping (it has a one-way piston).
    I guess this topic came up as the comp damper mod is easy, so I (and others) were hoping a similar thing could be done with the rebound circuit. Maybe there is little to be gained. I can't help thinking that position-sensitive rebound damping is better that speed-sensitive (although the reverse may be the case for compression). Cheers, Steve

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    It's a poorly kept secret....

    Quote Originally Posted by cgd
    many thanks for the depth of your response, i was only ever aware that compression damping was controlled by orofice systems. how ignorant!

    thanks again.
    Die hard Manitou fans have known the secret of shim stacking for years... It's an art as well as a science!
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  74. #74
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    Quote Originally Posted by spacoli
    I'm no expert, but I would think it would be more controled and consistant with the shims. I thought that was the idea with a shim stack depending on the stack arangement. It would be just the opposite as is. there is a fixed piston that only lets so much oil pass through. The shims would bend and allow the oil to pass with the increase rebound speed at full compression.

    This maybe why Push does a two stage rebound? I know when I had my DHXC Pushed the rebound felt way slow. They told me not to worry, it's because of the two stage rebound, they explain why but I can't remember. The shock feels great to ride.

    You can not change the rebound piston. It would all need to be redesigned in order to make it work, as in make it all bigger diameter. Also to note that due to the size of the rebound piston you would n ot have enough room to design a two way valve that would 1 flow enough on the compression (blow-off) and then 2 have a shim big enough to be any better than what it is now. Maybe in the future but right now it is what it is.

    I know what you are trying to do, good idea, but not feesable with the size constraints of the current cartridge body.

    Tom MTD USA
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    Bugger!

    Quote Originally Posted by Marzocchi Tech Department
    You can not change the rebound piston. It would all need to be redesigned in order to make it work, as in make it all bigger diameter. Also to note that due to the size of the rebound piston you would n ot have enough room to design a two way valve that would 1 flow enough on the compression (blow-off) and then 2 have a shim big enough to be any better than what it is now. Maybe in the future but right now it is what it is.

    I know what you are trying to do, good idea, but not feesable with the size constraints of the current cartridge body.

    Tom MTD USA
    Oh well, there goes that idea! Thanks for at least stopping us wasting time on it, Tom. BTW, thanks for organising the new damper for my fork; since fitting it I have had zero problems and the fork feels very very nice. Looks like you've won me over to the dark (Marzocchi) side. Cheers, Steve

  76. #76
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    Quote Originally Posted by Stevo the Devo
    Hey Cesper,
    Unfortunately the mod will not fix the hydro-lock problem, it can only be fixed by replacing the damper (or at least the bottom end cap) with the newer design. I would recommend contacting marz USA (or Marz Tech Dept on these forums) to arrange for a replacement under warranty before you do the mod. Cheers, Steve
    Hey Steve, I thought the hydro locking was caused by too much oil in the damper cart. I read that some oil could trickle in from the semi bath. But if the levels of both are corrected then how could the problem come back? With that being said, I am going to PM Tom about the new bottom nut. I'm guessing its recessed to contain an O ring to seal the shaft.



    Forgot to mention that i've put 20 miles on this fork and i'm not really missing my Magura Laurin. The Laurin felt a bit plusher on big hits but always seemed to blow through the travel and dive regardless of the psi. I'm running about 60 psi on the xc600 and its plush and not bottoming out. I think the addition of the coil spring in the air chamber is the key. I cant tell a different stiffness wise.
    Last edited by thebronze; 01-20-2009 at 11:59 AM.

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    I performed this mod last night and should add some notes here.

    I found it a hell of a lot easier to just remove the whole cartridge from the fork for the first time you do this. Marzocchi typically tightens the hell out of everything from the facotry, so you might be in for a lot of frustration trying the strap wrench method your first time. Slip off the rebound knob at the bottom, and use a 12mm socket on the lower nut. If you don't have an impact wrench or a high speed drill with a square drive adapter, it might not work out the best this way (or at all). Once you crack it a little bit loose, hit it with the drill. If it doesn't want to come off the very last bit, have someone pull upwards on the cartridge with some force while you hit it with the drill. Again, after the first time you disassemble everything removing the cartridge this won't be necessary, because....

    There are wrench flats! So place the lower wrench flat in a vice and pop the 27mm top cap out of the top of the cartridge. Then place the 27mm top cap wrench flats in the vice and remove the bolt head with a GOOD 10mm wrench. Don't use a 12pt for this if you can avoid it, because there is red loctite on that bolt and it's on there pretty good. Do your shim shuffling, and reassemble everything tight enough (not gorilla tight). Be sure to hit the bottom nut with a drill or impact wrench too.

    So, in the future, you can undo the top with a 27mm, then grab the cartridge body with a tube in your hand, remove the damper assembly with the 27mm, then do your thing and drop it back into the fork. Should take only a minute or so to get to the shims as long as you don't torque the living daylights out of everything upon reassembly.

    I haven't had a chance to mess with the shimstacks in it yet since I was shorter on my stock of smaller shims than I thought I was.

    Other notes: 50cc of lubricating oil in the right fork leg, and 75-80cc of oil in the cartridge yields exactly 110mm of oil height.

    Has anyone removed the bottom cap of the cartridge body (where the shaft goes through, the one with the wrench flats)? Also, can anyone identify what the threads are on the top cap to the fork leg, and the threads on the bottom of the upper cartridge tube (to the shaft cap)? I have a project in mind for this cartridge which would require me to order some new tubing for it...
    805

  78. #78
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    Quote Originally Posted by DHidiot
    I performed this mod last night and should add some notes here....
    Nice! Thanks for the tips and adding to the document.

    Let us know what you used for your shim stack and what your results are.

    I've no clue about the threads, and it is just a few minute job to get into the cartridge after the first time.

    P

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    I only put 2 18mm shims in the fork as a temporary fix (this wasn't my fork) until we can get a more appropriate stack going on. Will probably start at 18 18 17 16 15 13 for some more low/mid speed support and more blowoff towards the high end. That piston could probably benefit from some mild porting work too.
    805

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    Has anyone removed the bottom cap of the cartridge body (where the shaft goes through, the one with the wrench flats)? Also, can anyone identify what the threads are on the top cap to the fork leg, and the threads on the bottom of the upper cartridge tube (to the shaft cap)? I have a project in mind for this cartridge which would require me to order some new tubing for it...[/QUOTE]

    HI DHI,
    The bottom cap you are referring to is the rebound circuit of the damper, and it can be removed relatively easily using the strap wrench method. There is a chance that if you use the flats here to hold the damper whilst undoing the top cap that you will actually remove this instead of the compression damper; it just depends on which one is tighter (for you, obviously the bottom nut was tighter than the top). When referring to the threads at the top, are you after specific pitch info? if so, I'm afraid I can't help, but you should be able to buy a thread gauge fairly cheaply at a hardware store. Hope this helps, keep us all posted on tuning results.
    Cheers, Steve

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    Yes that bottom one is a lot tighter. I also just held the cartridge body still when I had that part in the vice to make sure it was the top that came loose (wasn't necessary but did it anyway just when it broke loose).

    I was thinking of the thread gauge idea too actually, but I didn't know if they would be too fine to read (I've only had to use a thread gauge once or twice).
    805

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    Hi, and thanks for everybode involved for figuring all this out. After I saw this thread and noticed there are still some -08 55 TST2 forks on sale for really good price this is getting really interesting. But I have some guestions and things I need to consider before I go shopping.

    - What is the real weight of a -08 55 TST2 fork (Yes I'm bit of an weight weenie)?
    - There is a coil spring only in left leg?
    - Is the left leg filled with oil like old open oilbath bombers, or is there just some 50ml of oil for lubrication?
    - Does someone have an idea about what ATA cartridge (used in 55 TST micro ATA) would cost? (Now some may ques what I'm going for)
    - Has someone been able to compare the performance of a 55 TST2 with modified damper to 55 TST micro ATA, Fox Float 36 RC2 or Talas 36 RC2? I mean can the TST2 be modified to be on bar with these more expencive forks or is there still a clear performance gain in higher end models.

  83. #83
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    Coil only in the left leg, believe it had 200cc of oil per the website's numbers (the right leg with the damper has 50cc lubricating oil in the leg itself, more in the damper). Ask MTD (Tom) about the cost for an ATA cart.
    805

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    I'm the guy who's fork DHI worked on. Tomorrow I'll order more shims and mess around with it next week. Maybe even bring tools on a ride and play with different setting. With new oil the fork felt much smoother. Can't wait to ride it this weekend.

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    I should also mention I used Showa 10w (SS-8?) oil in the damper since Nags is a bigger dude. Of course I also seem to notice that most Marzocchi's except the RC2 cartridges feel better with heavier oil than stock too, but that's just me.
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    Quote Originally Posted by TeXe
    Has someone been able to compare the performance of a 55 TST2 with modified damper to 55 TST micro ATA, Fox Float 36 RC2 or Talas 36 RC2? I mean can the TST2 be modified to be on bar with these more expencive forks or is there still a clear performance gain in higher end models.
    No comments for this?

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    Quote Originally Posted by TeXe
    Has someone been able to compare the performance of a 55 TST2 with modified damper to 55 TST micro ATA, Fox Float 36 RC2 or Talas 36 RC2? I mean can the TST2 be modified to be on bar with these more expencive forks or is there still a clear performance gain in higher end models.
    The way I understand it, Marzocchi's RC3 and Fox's RC2 will have more buttery feel than my mod (I haven't tried TST Micro). RC3 & RC2 dampers have only the compression piston moving in an oil bath, while the TST moves the damping oil through a stationary piston. Pushing the oil will have a bit of an impact.

    But the TST mod gives you compression adjust within hand reach during riding. I find that useful for various terrain. The mod also allows you to set the shim stack to your riding.

    For more consistent, big and square hit terrain the RC3/RC2 is probably better.

    For my style riding/terrain the performance difference and the benefits to having compression on top means I will stick with the TST mod.

    The forks in your question have different spring characteristics, which will make the forks behave very differently.

    P

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    Quick thanks to Tom who sent me a whole new TST2 cartridge for free. The new cart has a revised bottom cap which should seal out the semi bath better. Now I have another piston that I can custom valve for certain trails. I just revalved the stock tune by adding another 18 and 17mm OD. I'm pretty sure i'm using 18, 18, 17, 17, 16, 14, 12 and the stock washer, which was about 10mm od.

  89. #89
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    Quote Originally Posted by spacoli
    I still have one, mint condition, qr axle though. I'm hoping for the same results. Can anyone compare the two?
    I think the modded tst2 is better because it has adjustable low speed compression, rebound, and a fully customized shim stack. The compression damping feels better and more controlled to me than hscv but not quite as smooth. I think thats due to the shims in the tst2 and the oil has a more complicated circuit to flow through. I remember when I took apart a broken HSCV cart and laughed. It just had a plastic piston in it and some kind of valve/shim in the bottom of it. I was expecting to find a piston similar to what is now in the tst2.

  90. #90
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    +1 for Tom. I told him about my fork and 3 three days later I had the part. Now it's my turn to play

    I think i'll just start with 2 18mm's, and go down from there.

  91. #91
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    Take a look at the third picture in here:
    http://www.declinemagazine.com/Nucle...hp?itemid=1915

    To me it looks like a TST2 lock out lever on the left leg. Makes you wonder that this mod might have been race proven by a quite succesful rider...

  92. #92
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    Quote Originally Posted by TeXe
    Take a look at the third picture in here:
    http://www.declinemagazine.com/Nucle...hp?itemid=1915

    To me it looks like a TST2 lock out lever on the left leg. Makes you wonder that this mod might have been race proven by a quite succesful rider...
    That would be cool!

    I am pretty sure Tom worked with Brain Lopes to set up his suspension.

    P

  93. #93
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    Hmmmm

    Couple of questions?

    What stack would be recommended to take the harshness of the low speed compression

    Is this a job that can be done by a weekend mechanic?

    Where can I get the shims from?

    cheers Guys

  94. #94
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    Quote Originally Posted by SinbadIOM
    Couple of questions?

    What stack would be recommended to take the harshness of the low speed compression

    Is this a job that can be done by a weekend mechanic?

    Where can I get the shims from?

    cheers Guys
    This mod is to bring enhanced effect to the high speed damping. In stock form, low speed damping is minimal if you have the LO open.

    If you've taken apart a fork to service it before, you can probably do this. But I would not crack open a fork for the first time and mod it too. IMO, it would be too much.

    Shims can be had at www.mxtech.com

    P

  95. #95
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    Quote Originally Posted by thebronze
    I remember when I took apart a broken HSCV cart and laughed. It just had a plastic piston in it and some kind of valve/shim in the bottom of it. I was expecting to find a piston similar to what is now in the tst2.
    Hmm, I'm not sure if you actually did this. To get at the HSCV valve you have to saw-apart the cartridge, because it's not user-servicable and it's bonded together. The hscv piston is made of metal has two shims on either side, one should be for rebound and one should be for compression. There's an o-ring in the middle of it. It is really low-tech, with no fancy damping like you'll find with RC3 or any fox damper, but your description doesn't fit with it. I've taken a picture of it before, it might even be in this thread.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

    You're turning black metallic.

  96. #96
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    Quote Originally Posted by Jayem
    Hmm, I'm not sure if you actually did this. To get at the HSCV valve you have to saw-apart the cartridge, because it's not user-servicable and it's bonded together. The hscv piston is made of metal has two shims on either side, one should be for rebound and one should be for compression. There's an o-ring in the middle of it. It is really low-tech, with no fancy damping like you'll find with RC3 or any fox damper, but your description doesn't fit with it. I've taken a picture of it before, it might even be in this thread.
    It wouldn't be the first time that Marzocchi does the same part with different specs...

    I had a serviceable ETA cart which is not found easily. It could be something OEM where they skimped on features.
    Check my Site

  97. #97
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    Quote Originally Posted by Jayem
    Hmm, I'm not sure if you actually did this. To get at the HSCV valve you have to saw-apart the cartridge, because it's not user-servicable and it's bonded together. The hscv piston is made of metal has two shims on either side, one should be for rebound and one should be for compression. There's an o-ring in the middle of it. It is really low-tech, with no fancy damping like you'll find with RC3 or any fox damper, but your description doesn't fit with it. I've taken a picture of it before, it might even be in this thread.
    I cut mine open with a pipe cutter. The actual cart body had ruptured and I had to buy a replacement kit. It was an ebay fork and I can only guess what you'd have to do to rupture the metal like that. From what I can remember, there were no shims, and no o ring. There was a plastic glide ring on the piston similar to the teflon seals in fox, but it was white not blue. There was something in the bottom of the cart that looked like a second piston. I guess that might be where the shims are but it was attached and would not come out. It was definitely low tech. I may have the bits in the garage still. Not sure if it matters, but this was a z1 qr 130 from 2002/3 era with rebound on top of the hscv R leg.

  98. #98
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    Can anyone post the part numbers for the items needed for the lock-out to a low speed compression adjustment and adds a high-speed compression shim stack? Also what kind of oil do you recommend? Thanks
    Last edited by Supple1; 03-04-2009 at 06:30 PM.

  99. #99
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    There are no part numbers from marzocchi. You'll need to buy some shims to replace the stock washers that are blocking the compression ports on the piston. The low speed will flow through the tst port. I think my baseline stack is
    18
    17
    16
    16
    14
    12
    I'm using redline 10 wt synthetic oil, but I weigh 205. I may double the 17 or swap the 18 to a thicker shim in the future. All shims are 8mm inside diameter, .10mm thick. Your stack and oil weight/blend will probably be different than mine based on your needs but less us know what your after and we could try to suggest a baseline.
    /t

  100. #100
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    Quote Originally Posted by thebronze
    There are no part numbers from marzocchi. You'll need to buy some shims to replace the stock washers that are blocking the compression ports on the piston. The low speed will flow through the tst port. I think my baseline stack is
    18
    17
    16
    16
    14
    12
    I'm using redline 10 wt synthetic oil, but I weigh 205. I may double the 17 or swap the 18 to a thicker shim in the future. All shims are 8mm inside diameter, .10mm thick. Your stack and oil weight/blend will probably be different than mine based on your needs but less us know what your after and we could try to suggest a baseline.
    /t
    Thanks! I am 175 w/ pads and a moderate to aggresive rider

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