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  1. #1
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    Marzocchi 55 TST2 set-up help needed

    edit: UPDATE TO ORIGINAL POST BELOW WITH NEW SETTINGS: click here

    edit: UPDATE 2: TST2 damper pics

    edit: UPDATE 3: Possible modification

    edit: UPDATE 4: New settings and results. Cliff Notes version:
    .....Final opinion is that the damper's high speed compression is a bit over the top, not horrible for fast descending - but not great either, but the HSC rocks the freeride stuff!....


    I love the way the 55 TST2 handles big hits and has a pretty controlled behavior.

    But, I'm not diggin' the harsh small bump compliance at speed. Fast boneyards, braking bumps, etc. the fork feels like it is hydraulically locking up similar to a port orofice damper

    I have tried varying air pressures for preload:
    - 10 psi removes harshness, but the fork then behaves like it is undersprung (dive, weak midstroke, etc)

    - 28 psi feels more like the correct spring rate, but I get that hydraulically lock feel in the fast rough stuff

    I've checked oil levels, and am getting ready for the fork's first oil change (about 9 hours ride time). Oil level is currently at 55mm from top.

    I run my rebound pretty fast, but have not yet tested if I could run it faster in the high speed conditions to improve the situation.

    I think it might be the air preload side, as the open bath system might create some of this harsh feel at speed.
    (I am thinking this as the TST 2 damper does not have the harshness when under sprung (10 psi) - the TST2 damper seems to have piston/shim feel to it. Or maybe I am just feeling the air spring deep travel ramp-up on drops. And it really is an orofice damper :-( )

    Would running a lighter oil on the air preload side improve plushness in rough, high speed situations?

    If so what oil should I use?
    Marzocchi oil is Golden Spectro Cartridge Fork Fluid 7.5w (125/150), should I use Golden Spectro Cartridge Fork Fluid 7.5w (85/150)? or another? http://www.spectro-oils.com/products...n/cartfork.asp

    Thanks for any help.

    P
    Last edited by Mr.P; 03-30-2008 at 09:30 PM.

  2. #2
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    Mr P,
    I agree 100% the fork is great for big hits! However, I don’t think the fork will ever be super plush on high speed bumps... at least with either of two cartridges I have ridden. (TST2 & R) We have tried zero and even negative pressure as well as 30 psi… harsh, harsh, harsh! And there will come a time when it get’s even worse… It’s a subtle change not something that seems to happen all at once. (Has happened to be twice)

    First time it blew my TST, all I noticed was the fork would not bottom. Normally I would bottom the fork as least once a ride, then all the sudden I could not reach the last inch or so of travel. I let all the air out and still could not bottom the fork. Sent it to Marzocchi and they installed a new cartridge. (At this point I had been riding the fork about 2 months and had logged about 150 miles) My normal air pressure was around 7 PSI.

    Got the fork back and it was smooth as a baby's butt in the high speed bumps, this was when I realized just how rough the fork was before. back to riding with about 7 PSI and getting 160mm travel. I managed to put another 150 miles or so on the fork, before I once again noticed the fork would not bottom, rode the fork anyway as it was a weekend trip… Fork was harsh in the small stuff, but handled the big hits just fine. Travel was limited to 140-150mm. I can’t really tell you the change took effect on one ride or in one week, it’s more like it happens over several rides and weeks. It’s like all the sudden you realize something just aint right and then you realize the fork travel is limited and the ride is harsh... I let all the air out and tried to force the fork to the bottom, no-go.

    I have a new TST2 cartridge in my possession, going to remove the old and have a look inside… Anyone interested in photos of the inside of the TST2?

    One other thing: one of my riding buddies blew his 55R damper… I helped him install the new one… could not see what’s inside as it is sealed… looks just like the hydraulic cylinder used to hold up a hatchback except both ends are threaded. You can compress the R cartridge but let it go and it will extend... I will say his 55R is just as harsh as the TST2 in small bumps, so you may well be on to something with your statement: “I think it might be the air preload side, as the open bath system might create some of this harsh feel at speed.”

    I have not seen the inside of the 55TST but I will soon… I have photos of the inside of the 55R and I will post both here on your thread… give me a couple of days.

    I don’t know much about forks or shocks but maybe if I post some photos someone will suggest modifications? Life is just a big experiment anyway, so why not modify?

    Good News on the horizon: Marzocchi is going to release a RC2 version of the fork this fall… so maybe we can change the internals of our TST…

    I am not a man of patience… fall is to far away… I am now riding a 66 RC3! 55 is in the closet

  3. #3
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    Quote Originally Posted by flyag1
    Mr P,
    I agree 100% the fork is great for big hits! However, I don’t think the fork will ever be super plush on high speed bumps... at least with either of two cartridges I have ridden. (TST2 & R)
    Thanks for the feedback! I was just reading your posts today, and was playing with lower pressures as a result.

    I responded to one of your posts a few months back where you described the small bump feel, and I bought the fork anyway...

    And you are not the only one that has had a bad damper....

    grumble.... grumble....

    But I like the fork for all but the high speed spiking...

    P

  4. #4
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    Quote Originally Posted by flyag1
    I have a new TST2 cartridge in my possession, going to remove the old and have a look inside… Anyone interested in photos of the inside of the TST2?
    I would love to see those insides. It would tell me if what is wrong is my set up (piston/shim damper) or it's the damper (orifice damper).

    P

  5. #5
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    Quote Originally Posted by Mr.P
    I would love to see those insides. It would tell me if what is wrong is my set up (piston/shim damper) or it's the damper (orifice damper).

    P
    I wondered if you noticed that statement? I will be changing my cartridge soon and will post images here for all to enjoy....

    Are you getting full travel on your fork?

  6. #6
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    Quote Originally Posted by flyag1
    I wondered if you noticed that statement? I will be changing my cartridge soon and will post images here for all to enjoy....

    Are you getting full travel on your fork?
    Me likey pictures thanks!

    I just checked the travel and I get full travel.

    Gotta ask how the 66 RC3 is?

    P
    Last edited by Mr.P; 03-17-2008 at 10:48 PM.

  7. #7
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    I haven't worked on the newer tst systems, but have on the old tst that came on 05 and 06 all mountain 1's. My brother has one of each, and I have changed the oil in the open bath and cartridge for him. I replaced the open bath with 5 wt silkolin (I'm not sure what the correct spelling is, and i'm to lazy to look it up), from the stock 7.5 golden spectro, and replaced the cartridge oil with 2.5 golden spectro. The forks became much more lively, and less harsh. Before the only setting on the 5 tst that was operable was full open. After the second setting also worked when less brake dive was needed.
    So if it's possible try swapping out the cartridge oil for a lighter oil.
    Bunk
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  8. #8
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    Quote Originally Posted by farmboybunk
    I haven't worked on the newer tst systems, but have on the old tst that came on 05 and 06 all mountain 1's. My brother has one of each, and I have changed the oil in the open bath and cartridge for him. I replaced the open bath with 5 wt silkolin ...
    Bunk

    Thanks! That is helpful. I think the TST damper is a closed unit for Marz only service. I hope not, as I would like that adjustability and frequency of service for myself.

    Like your experience, I am only getting noticeable full open or lock-out, can't really feel a difference with the settings in between.

    It'll be interesting to see the cartridge innards when flyag1 posts with the pics.

    P

  9. #9
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    Update To Original Post

    UPDATE

    I was able to ride the same trails and stunts as my original post but with different settings, based on feedback and my own feel.

    The spring side oil weight has no relationship to damping as far as I can tell so I was way off base on that one.

    I lowered air pressure to ~22psi, oil level at 55mm and sped up rebound. Pre-ride I turned the bike (fork) upside-down for 30 seconds and cycled the fork an inch or two a couple times. This gets a fresh coating of oil to the upper seals and stanchions eliminating stiction thereby greatly increasing small bump compliance, especially at low speed.

    I am happy to report that small bump compliance has improved while maintaining big hit capabilities. Stiffening through the boneyards is greatly reduced, tho a bit still remains (but it feels similar to a 36 Van I've ridden, and a TPC+ Nixon). The stiffening now feels more "fluid" than the "spiking" of my previous report - firm but not harsh.

    I think I had the fork over-sprung and perhaps a bit over-damped in the rebound circuit.

    For me (180#, 06 Enduro, ride fast straight through boneyards, jumps, etc.) the recommended air pressure (0-15 psi) is too low. It felt to undersprung and gave no pop for jumps or bunny hops - while my rear had pop = Mismatch! Yikes!

    So great improvement with better settings. I still have more tuning which should improve things a bit. Next up is to lower the oil level to get closer to full travel, and should reduce some of the spring rate ramp-up in mid-stroke that affects the fast bump compliance. Bottom line is that this was ride #4 and things should improve from here as I keep noodling and the fork breaks in more.

    P

  10. #10
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    Cartridge from 2008 Marzocchi TST2

    [IMG][/IMG]

  11. #11
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    2008 Marzocchi 55R

    [IMG]Photobucket[/IMG]

    [IMG]Photobucket[/IMG]

  12. #12
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    Quote Originally Posted by flyag1
    Cartridge from 2008 Marzocchi TST2
    [IMG][/IMG]
    Hmmm. That is interesting. Looks kinda like a TPC set-up - set top piston separated from the rebound and oil gets pushed up.

    Can't tell if it is a orofice or piston/shim damped.

    P

  13. #13
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    Quote Originally Posted by flyag1
    2008 Marzocchi 55R

    [IMG]\>[/IMG]

    [IMG]\[/IMG]
    I am surprised by the "R" cartridge. I expected it to just be neutered TST2, but it looks very different.

    Thanks so much for the pics flyag1 !



    P

  14. #14
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    TST2 Cartridge insides!

    flyag1 sent me these pics of the inside of the TST2 damper and did my best to point out the different functions.

    We both have questions as to how the damper locks out as the lock-out orifice is on a separate top piston assembly rod than the compression piston and shim which is on the bottom assembly.

    The good news: TST2 has piston/shim damping for both compression and rebound.

    The bad news: how can such a simple looking system have the number of failures that are showing up?

    I'll let the pics speak for themselves.

    Thanks to flyag1 for taking the damper apart and for taking the time to take such great pics

    P

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    Last edited by Mr.P; 03-27-2008 at 10:26 AM.

  15. #15
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    Quote Originally Posted by Mr.P
    flyag1 sent me these pics of the inside of the TST2 damper and did my best to point out the different functions.

    We both have questions as to how the damper locks out as the lock-out orifice is on a separate top piston assembly rod than the compression piston and shim which is on the bottom assembly.

    The good news: TST2 has piston/shim damping for both compression and rebound.

    The bad news: how can such a simple looking system have the number of failures that are showing up?

    I'll let the pics speak for themselves.

    Thanks to flyag1 for taking the damper apart and for taking the time to take such great pics

    P

    Bro, that's great info...

    However, I think you have it a bit mixed up. The piston on with the lockout is indeed the compression. All open with just a stiff blow-off when you close it. Very ETA-like.

    The rebound is the lower piston... What you see with the spring washers are just check valves (one way valves) that allow free flow in one direction and restrict the flow in the opposite.

    How this simple system can fail by limiting travel little by little?? I have no clue... Other than oil migrating from the semi-bath to the cartridge. Because high oil from the get go, will just limit travel from the first time you use the fork.

    Maybe air build up in the cart as in MX forks???

    Also, I don't see special tools needed to service it and looks dead easy to work on, but you can confirm if that's true or not.
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    Thanks Warp,

    The cartridge was very easy to open... just unscrew the both ends off a threaded tube... and your done... I do understand the (top) thing-a-ma-gig is the compression side and lock out... whereas the bottom is the rebound... and the check valve in the rebound side makes perfectly good sense as does the restrictor needle.

    However the top thing-a-ma-gig (lock out and compression) is not computing.... maybe I don't understand the fluid levels? should the cartridge be completely full of oil?

    If the answer is yes: then closing the the TST valve... (turning the lock out to the closed position) you basically block the top 50% of the cartridge... as if the cartridge is now only 1/2 it's original length... and the bottom 50% should still function normally.

    If the top 1/2 of the cartridge is air filled then we have a different animal. It this is the case, then on really big hits fluid could be pushed into the air chamber which could result in a negative pressure below the rebound piston. Basically the top portion of the cartridge becomes a blow off reservoir and without the extra volume the orifices in the rebound piston (check valve and needle) will dramatically restrict fluid movement.

    In second scenario: where there is air in the top 1/2 of the cartridge... and a negative pressure below the piston is possible... then failure of the cartridge performance can be induced by the vacuuming of oil into the cartridge from the oil in the lower portion of the fork. Basically, the seals in the lower porting of the cartridge allow the lubricating oil in the lowers to be sucked up into the cart... resulting in cartridge overfilling and loss of travel.

    How is that for root cause analysis? To prove the point, just put red oil in fork lowers and clear in cartridge, when cartridge fails then open cartridge and most likely you will find red die in cartridge oil. Tell Marzocchi to install two way seal in lower cartridge and issue fixed!

    Now we can start to work on a fix for small bump compliance?

  17. #17
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    Quote Originally Posted by Warp
    Bro, that's great info...

    However, I think you have it a bit mixed up. The piston on with the lockout is indeed the compression. All open with just a stiff blow-off when you close it. Very ETA-like.

    The rebound is the lower piston... What you see with the spring washers are just check valves (one way valves) that allow free flow in one direction and restrict the flow in the opposite.

    How this simple system can fail by limiting travel little by little?? I have no clue... Other than oil migrating from the semi-bath to the cartridge. Because high oil from the get go, will just limit travel from the first time you use the fork.

    Maybe air build up in the cart as in MX forks???

    Also, I don't see special tools needed to service it and looks dead easy to work on, but you can confirm if that's true or not.
    I think you are right, that those piston/shims are check valves. Doh! That means the damping is orifice based. Boooo! That means only an oil weight change will affect the high speed spikes. Booo! 2008 and still orifice dampers.

    Unless.... Those gigantic blow off shims get replaced with a proper shim stack.... Possible? The orifice already flows so much oil... And why make the blow-off so heavy duty any way. Marzo told me on the phone that mid-setting lock out was a bad idea during non-climbing, even tho there is a blow-off, it could crap the damper...

    P

  18. #18
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    Quote Originally Posted by flyag1
    Thanks Warp,

    The cartridge was very easy to open... just unscrew the both ends off a threaded tube... and your done... I do understand the (top) thing-a-ma-gig is the compression side and lock out... whereas the bottom is the rebound... and the check valve in the rebound side makes perfectly good sense as does the restrictor needle.

    However the top thing-a-ma-gig (lock out and compression) is not computing.... maybe I don't understand the fluid levels? should the cartridge be completely full of oil?

    If the answer is yes: then closing the the TST valve... (turning the lock out to the closed position) you basically block the top 50% of the cartridge... as if the cartridge is now only 1/2 it's original length... and the bottom 50% should still function normally.

    If the top 1/2 of the cartridge is air filled then we have a different animal. It this is the case, then on really big hits fluid could be pushed into the air chamber which could result in a negative pressure below the rebound piston. Basically the top portion of the cartridge becomes a blow off reservoir and without the extra volume the orifices in the rebound piston (check valve and needle) will dramatically restrict fluid movement.

    In second scenario: where there is air in the top 1/2 of the cartridge... and a negative pressure below the piston is possible... then failure of the cartridge performance can be induced by the vacuuming of oil into the cartridge from the oil in the lower portion of the fork. Basically, the seals in the lower porting of the cartridge allow the lubricating oil in the lowers to be sucked up into the cart... resulting in cartridge overfilling and loss of travel.

    How is that for root cause analysis? To prove the point, just put red oil in fork lowers and clear in cartridge, when cartridge fails then open cartridge and most likely you will find red die in cartridge oil. Tell Marzocchi to install two way seal in lower cartridge and issue fixed!

    Now we can start to work on a fix for small bump compliance?
    The way I understand it, it works like a rear shock but with no separating (at least not floating) piston between the air and oil.

    Oil (and I have no experience at all with the TST2, so take it with a grain of salt) should be just covering the compression piston. As the plunger shaft that holds the rebound piston enters the cart, it will displace oil and occupy space into the air chamber.

    If you lock it, you just prevent oil from displacing and it will flow only if you go over the blow off threshold. Oil can flow back down thanks to the check valve.

    If you have the oil lower than the piston, then you can have the problems you're mentioning.

    For small bump compliance, try a pressure (the cartridge is pressurized, right??) lower than indicated and/or a lighter oil than stock.
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  19. #19
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    Quote Originally Posted by flyag1
    In second scenario: where there is air in the top 1/2 of the cartridge... and a negative pressure below the piston is possible... then failure of the cartridge performance can be induced by the vacuuming of oil into the cartridge from the oil in the lower portion of the fork. Basically, the seals in the lower porting of the cartridge allow the lubricating oil in the lowers to be sucked up into the cart... resulting in cartridge overfilling and loss of travel.

    How is that for root cause analysis? To prove the point, just put red oil in fork lowers and clear in cartridge, when cartridge fails then open cartridge and most likely you will find red die in cartridge oil. Tell Marzocchi to install two way seal in lower cartridge and issue fixed!

    Now we can start to work on a fix for small bump compliance?
    Brilliant! Too much oil make sense. I just found this on Dougal's Manitou FAQs page:
    TPC manitous also need a large air space in the damper. This is because they work on displacement (volume change) and the oil level rises in the stanchion as the fork compresses.
    Too much oil causes hydraulic lock, too little causes cavitation and both can damage your fork.
    Great to know the damper is an easy break down.

    It seems the air springs in the ATAs are having issues. I wonder if the seals Marzo (Suntour) is getting are poor spec. Like the Fox "stuck down" epidemic of a few years ago (at least that was the official line).

    I dunno on the small bump compliance, I can only guess it is the air preload seals.

    P

  20. #20
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    Quote Originally Posted by Mr.P
    I think you are right, that those piston/shims are check valves. Doh! That means the damping is orifice based. Boooo! That means only an oil weight change will affect the high speed spikes. Booo! 2008 and still orifice dampers.

    Unless.... Those gigantic blow off shims get replaced with a proper shim stack.... Possible? The orifice already flows so much oil... And why make the blow-off so heavy duty any way. Marzo told me on the phone that mid-setting lock out was a bad idea during non-climbing, even tho there is a blow-off, it could crap the damper...

    P
    You're on the right track, P.

    Indeed, you would improve the damper by adding shims and closing a bit the main orifice.

    I don't know why the stiff blow off... The TST5 is equally stiff.
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  21. #21
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    More pics!

    flyag1 sent over some more pics for posting.

    They can speak for themselves.

    Tuning options on the damper seem to include:
    - lighter weight oil (the ham fisted approach - but effective)
    - modify the blow off with a thinner and perhaps pyramid shim stack ( I guess one would have to start with a good amount of shims based on what is stock)

    Anyone else with any more ideas?

    P
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    Potential Improvement to Damper

    So I got thinking about the blow off to shim stack, and began to think it is quite feasible.

    After all it would only be used when the oil pressure starts to spike.

    By putting lighter shims in a pyramid stack, lockout would be more like a platform, and high speed compressions would be directed through the shim stack reducing spikes. Does this sound accurate?

    Anyone have any thoughts on implementation? It's so easy to think about but reality is a bit different

    Pics of potential change below.

    flyag1 measured out the stock blow off shims:
    "There are actually 4 shims in the factory stack, (0.32 ID X 0.790 OD x 0.016 thick)"

    One other possibility would be to reduce to blow off shim stack to just one shim. It would not be a progressive stack but working in conjunction with the orifice damper, might reduce the high speed spikes. Thoughts anyone?

    Flyag1, was there any nitrogen in the cartridge? And if it is a seal issue that makes the cartridges crap out, any way for us to fix on a more permanent level?

    P
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    Last edited by Mr.P; 03-29-2008 at 08:37 AM.

  23. #23
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    UPDATE: New settings, damper info and ride report

    Another ride Another tweak.

    The Cheese gave me a good tip to lower my oil height (while at same psi) to reduce down the spring rate mid-stroke. It was on the to-do list as my 55mm (Marz rec) height was not giving me full travel (about 30mm short), but his input made me be a bit more aggressive.

    Settings:
    23psi, oil height 62mm, rebound fast as reasonable

    So I took the spring out and reduced the oil level to 62mm from crown.

    While the spring was out, I decided to run some tests on the damper:

    - no spring (coil & air), damper open = damper gets progressive at 60mm to bottom. Progressive to the point where it requires my full body weight to reach bottom. Air or nitrogen compression in damper? Me thinks less need for spring progressiveness. EDIT: it is the air in the damper side leg that was creating the progressiveness.

    - no spring (coil & air),damper closed to lock out = super damped but still travels, rebound is damped normally.

    Ride results:
    - Same trail as all above.
    - 150mm travel with a nose heavy landing on a 4' drop. I'll save that last 10mm for a nasty oops incident.
    - Small stuff at a moderate speed was invisible (I think my turning the fork upside down to lube the bushings helped the small bumps)
    - 2-3" rocks at high speed were firm, but did not feel spiked like an RV type damper
    - I nose heavied a 4' drop, over shot the landing on a 6' gapper, poorly landed a near flat landing and the fork just sucked it up without complaint. I love this fork for that.

    So, final opinion is that the damper's high speed compression is a bit over the top, not horrible for fast descending - but not great either, but the HSC rocks the freeride stuff!

    I need to try this fork at Downieville - which can get very fast and rough - to see if it is a keeper.

    Also, if the damper craps out on me, I might just try adjusting the blow off to a firm shim stack.

    I want to keep the lock out as it can make a fast & efficient ascender on short out of saddle steeps. Never thought I would say that about a 160mm fork.

    P
    Last edited by Mr.P; 03-31-2008 at 10:07 AM.

  24. #24
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    Quote Originally Posted by Mr.P
    Another ride Another tweak.

    spring (coil & air), damper open = damper gets progressive at 60mm to bottom. Progressive to the point where it requires my full body weight to reach bottom. Air or nitrogen compression in damper? Me thinks less need for spring progressiveness.

    high speed compression is a bit over the top, not horrible for fast descending - but not great either, but the HSC rocks the freeride stuff!

    P
    Mr P,
    TST cartridge has no charge (no air... no nitrogen)

    Yes the fork does get progressive... even with the spring side open,but it's not the TST cartridge. It's the fork leg itself, as it is sealed. Larger oil volumes in the fork legs will also allow greater buildup pressures inside the fork. Need a stiffer fork, add oil...need more travel and a softer ride take away oil....

    It's even possible to have negative pressure in the right side of the 55 TST. To set up negative, remove cap and spring from left side... unscrew cap from TST side and compress fork and press the top cap of the TST cartitdge back into the right leg and re-tighten the top cap. Try to extend the fork and you will find if very difficult as the negative pressure will not allow you to do so....
    Negative pressure could be used to decrease Crown to axle length?
    Negative pressure could be used as a top out bumper?
    Maybe the negative would provide small but plushness?
    Of course, negative pressure would decrease usable travel.

    I totally agree the shims are causing issues with high speed plushness. As you suggested I am experimenting with a lighter pyramid shape compression stack of shims, backed by a heaver stack. In theory small hits only require small volumes of oil movement, where as big hit will require larger volumes. The lighter shims at the beginning of the stack should allow small volumes of oil to pass the compression piston with very little resistance. The heaver shims behind the lighter stack should restricting total volume and induce pressure buildup inside the TST cartridge for big hits Hence: progressive travel... The air pressure buildup inside the sealed legs will aid in the progressive travel as well....

  25. #25
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    Quote Originally Posted by flyag1
    Mr P,
    TST cartridge has no charge (no air... no nitrogen)
    Great info, thanks. So it is filled to the brim with oil. Doesn't the oil need a space to fill on compression?

    Quote Originally Posted by flyag1
    Yes the fork does get progressive... even with the spring side open,but it's not the TST cartridge. It's the fork leg itself, as it is sealed.
    Doh! I forgot about the cartridge side!

    Quote Originally Posted by flyag1
    It's even possible to have negative pressure in the right side of the 55 TST. To set up negative, remove cap and spring from left side... unscrew cap from TST side and compress fork and press the top cap of the TST cartitdge back into the right leg and re-tighten the top cap. Try to extend the fork and you will find if very difficult as the negative pressure will not allow you to do so....
    Negative pressure could be used to decrease Crown to axle length?
    Negative pressure could be used as a top out bumper?
    Maybe the negative would provide small but plushness?
    Of course, negative pressure would decrease usable travel.
    Very clever! I did something similar to my wifes fork, only created negative pressures on both sides to reduce coil spring rate. It worked great for her.

    I wonder if this could work for small bump stuff? I bet it would. It might pull down the sag a bit, but the key would be to find that perfect balance between left and right leg pressures.

    Or maybe just get a custom made coil for the coil side, no longer use the Air Preload, and let the static pressures add the progressiveness.

    There is already a coil negative spring on the coil side.

    P
    Last edited by Mr.P; 03-31-2008 at 09:38 AM.

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