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  1. #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-post4289055.html 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

  2. #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.

  3. #28
    cgd
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    can someone please tell me in laymans terms what these shims do and how they do it?

  4. #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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  5. #30
    cgd
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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.

  6. #31
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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?

  7. #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

  8. #33
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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

  9. #34
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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!!

  10. #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

  11. #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.

  12. #37
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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.

  13. #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.

  14. #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

  15. #40
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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...

  16. #41
    SLX
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    Great post!.! Thanks for the advice.
    Leave no bolt untuned!

  17. #42
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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!

  18. #43
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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

  19. #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

  20. #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!

  21. #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

  22. #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.

  23. #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

  24. #49
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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

  25. #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...

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