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  1. #76
    PMK
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    I know this is the back end, I have another video showing it in square edge type terrain.

    This is Santos Spider Kingdom trail head west towards Landbridge.

    If you look close you see the tire sliding and kicking up stuff.

    http://vimeo.com/18418786

    This is what your fork has to keep up with.

    PK
    Last edited by PMK; 01-03-2011 at 11:30 PM.

  2. #77
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    Quote Originally Posted by reamer41
    Since changing oil I haven't had a chance to do anything.

    The rebound adjuster is at the bottom of the right leg. 6 turns, no clicks, from full open to full closed. Even with the 20wt, It seemed about right at about 1 or 2 turns back from full closed (from slow rebound).

    The left leg is spring only. No adjuster and, I think no damper rod.

    At one point I was running the air assist on the left leg (with reduced oil) and the spring preload adjuster on the right leg with the recommended 265cc oil. It worked OK, but at some point I switched back to air in both sides.

    This is what I wondered, the manual link, if it is correct is for a non rebound damping adjustable fork. This type fork is pretty basic damper rod design, mainly relying on freebleed holes (orifices) to control the damping.

    Per the Marz webpage archive, the damper has an SSV, problem is it's not tunable.

    I don't have magic settings for you. To optimize the fork will take a little effort, but once done you'll be able to repeat or tune from a good base point.

    PK

  3. #78
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    Quote Originally Posted by PMK
    This is what I wondered, the manual link, if it is correct is for a non rebound damping adjustable fork. This type fork is pretty basic damper rod design, mainly relying on freebleed holes (orifices) to control the damping.

    Per the Marz webpage archive, the damper has an SSV, problem is it's not tunable.

    I don't have magic settings for you. To optimize the fork will take a little effort, but once done you'll be able to repeat or tune from a good base point.

    PK
    Yeah, I forgot that the manual show that there is no adjuster. There is. The right leg has a knob on the bottom -- see picture. I don't know what's up with the manual -- otherwise it seems to be the same fork. Next time I have the fork apart I'll take pics of the damper rod. The first 3-4 turns of the damper adjustment seem to have no effect on rebound, but from 4 to 5 and 5 to 6 the effect is very noticeable.
    For part of the first ride with the new 20wt oil I had the damper adjusted 5 turns from full open and that may have contributed to harshness -- it may have been packing down at that setting.

    I pumped some of the 20wt out of the fork today. With springs removed and the fork compressed there was about 75mm from fluid to top of the tube. I took a guess, and fluid level is now 120mm from top. Stoker not available, but I did a solo test ride over some junk (bricks, 4x4s, etc...) I put in the road. The fork seems less harsh and is using more travel. Test ride tomorrow if I don't have to go to work.
    Attached Thumbnails Attached Thumbnails Suspension Fork Experience - What's Working? What's Not?-knob.jpg  

    Suspension Fork Experience - What's Working? What's Not?-fork.jpg  


  4. #79
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    Quote Originally Posted by PMK
    I know this is the back end, I have another video showing it in square edge type terrain.

    This is Santos Spider Kingdom trail head west towards Landbridge.

    If you look close you see the tire sliding and kicking up stuff.

    http://vimeo.com/18418786

    This is what your fork has to keep up with.

    PK
    Cool video! the shock sure moves a lot! The trails around here are rocky and rough. Maybe I'll rig a camera for similar footage.

    After I get the fork worked out I'll be looking for advice on optimizing the shock!

    the fifth video here: http://www.bikeradar.com/news/articl...-of-2010-28735 reminded me of your footage with the rear-facing camera.
    Last edited by reamer41; 01-04-2011 at 07:53 PM.

  5. #80
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    Everyone who's posted seems to be on 26er tandems... so what's hot and what's not as far as 29er tandems go? I want to avoid White Brothers & Maverick if only for the fact I'm in Hong Kong and should anything happen, getting them serviced will be a major PITA.

    The tandem team would actually be fairly light (<290lbs) but trails around this part of the world would want about 5in/120mm of travel. As much as I like Fox forks, their 29er stuff has too little travel and a 15mm axle would probably be too wimpy? Marzocchi 29er forks seem too XC as well (15mm axle again). Magura still don't have a 29er fork. So single crown wise it looks like it'd have to be a RockShox or a Manitou Minute/Tower (once that's released, with its tapered steerer) 29er?

    A Manitou Dorado Pro would obviously (obviously?) seem to be up to the task...though even as a 29er fork, it's got bucketloads of travel at 175mm... how difficult would it be to reduce it to a more sensible 130mm~150mm?

    *Forgot about the Manitou Tower 29er fork...

  6. #81
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    Quote Originally Posted by StanleyJ
    Everyone who's posted seems to be on 26er tandems... so what's hot and what's not as far as 29er tandems go? I want to avoid White Brothers & Maverick if only for the fact I'm in Hong Kong and should anything happen, getting them serviced will be a major PITA.

    The tandem team would actually be fairly light (<290lbs) but trails around this part of the world would want about 5in/120mm of travel. As much as I like Fox forks, their 29er stuff has too little travel and a 15mm axle would probably be too wimpy? Marzocchi 29er forks seem too XC as well (15mm axle again). Magura still don't have a 29er fork. So single crown wise it looks like it'd have to be a RockShox or a Manitou Minute/Tower (once that's released, with its tapered steerer) 29er?

    A Manitou Dorado Pro would obviously (obviously?) seem to be up to the task...though even as a 29er fork, it's got bucketloads of travel at 175mm... how difficult would it be to reduce it to a more sensible 130mm~150mm?

    *Forgot about the Manitou Tower 29er fork...
    I'll get clobbered for saying it but we run an ATC on our 29r Fandango hardtail and find it a good match for the bike, my stoker and I, plus the terrain we ride.

    With some simple details as I posted here our fork is easily up to the task and we have no plans to swap it.

    But...if you plan to run a 29r full suspension tandem, the fork will work decent, but may hold you back on serious terrain.

    As far as simplicity, this fork is as simple as an old school Manitou EFC.

    PK

  7. #82
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    Quote Originally Posted by reamer41
    I pumped some of the 20wt out of the fork today. ......fluid level is now 120mm from top. Stoker not available, but I did a solo test ride over some junk (bricks, 4x4s, etc...) I put in the road. The fork seems less harsh and is using more travel. Test ride tomorrow if I don't have to go to work.
    We got out for a ride yesterday. The fork was much better with the lower fluid level.
    Sag @ 1.25 inches (out of 5 total) 20psi air static air pressure.

    The fork felt good over everything except a rocky, twisty downhill piece. On that trail it was still not confidence inspiting. Too much compression dampening. Less so then with the 10wt oil. Everywhere else the 20wt seemed an improvement.

    I'll try the 15wt, and see how that is.

    Stupid question: If there is no damper in the left leg, no need to change that fluid, right?

  8. #83
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    Correct on the non damper side provided you don't change fluid level.

    Try 15wt, if that doesn't get it we can talk about making the fork more position sensitive.

    PK

  9. #84
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    All Right! I drained the 20wt on the right leg and replaced w/Maxima 15wt. Filled to 125mm from the top (previously 120mm, also dropped left leg to 125mm from top). We got a ride in yesterday and I think that this is a pretty good setup.

    The fork is still very compliant over small stuff, but doesn't blow through the travel easily, yet uses pretty much full travel on the big hits. Rocky , twisty, downhill felt as good as it's going to get I guess.

    I will do some experimenting with the rebound knob--last ride was at 4 turns (of 6) from full-open.

    Thanks for all your help and suggestions, PK.

  10. #85
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    Quote Originally Posted by reamer41
    All Right! I drained the 20wt on the right leg and replaced w/Maxima 15wt. Filled to 125mm from the top (previously 120mm, also dropped left leg to 125mm from top). We got a ride in yesterday and I think that this is a pretty good setup.

    The fork is still very compliant over small stuff, but doesn't blow through the travel easily, yet uses pretty much full travel on the big hits. Rocky , twisty, downhill felt as good as it's going to get I guess.

    I will do some experimenting with the rebound knob--last ride was at 4 turns (of 6) from full-open.

    Thanks for all your help and suggestions, PK.
    Your welcome.

    If you need more performance from it, let me know before you pull it apart next time. I'll have you measure a couple of things and see how that compares to how it doesn't meet your requirements.

    PK

    Wanted to add that with a non check valve design freebleed, the rebound adjustments will also, to some degree effect low speed compression damping. Faster rebound will soften the compression and firmer rebound will firm the compression. Most often not a problem, but still something to consider.

  11. #86
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    Seeing PMK's video of his rear shock in action inspired me to follow thru on videoing front and rear suspension action of the EDCM. Over all I'm pretty happy with how the fork is working. I think I'll I'll work on some fine-tuning, maybe either slightly increasing air pressure or raising fluid level slightly.

    Here's a link to the fork in action.

  12. #87
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    Quote Originally Posted by reamer41
    Seeing PMK's video of his rear shock in action inspired me to follow thru on videoing front and rear suspension action of the EDCM. Over all I'm pretty happy with how the fork is working. I think I'll I'll work on some fine-tuning, maybe either slightly increasing air pressure or raising fluid level slightly.

    Here's a link to the fork in action.

    For grins, could you measure from the bottom edge of the lower triple clamp to the top of the fork tube.

    I ask from seeing how much rubes are set above the upper clamp.

    There are some critical dimensions regarding this but also it can play into where the fork is truly settled in the stroke.

    The bottom out, while severe is not bad, it is "G"out followed by a step up. The most difficult terrain item for a tandem on a flowing trail in my opinion.

    With both springs removed, will the fork bottom on the internal bottoming cone or are the seals hitting the bottom of the lower triple clamp? Reference the manual link you posted, pages 9,10. They mention the notch in the tube and max headtube stuff.

    I'm suspecting the fork is too long and causing some of the concerns.. but the forks action looked pretty good.

    PK
    Last edited by PMK; 01-16-2011 at 11:14 AM.

  13. #88
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    Quote Originally Posted by PMK
    For grins, could you measure from the bottom edge of the lower triple clamp to the top of the fork tube.

    I ask from seeing how much rubes are set above the upper clamp.

    There are some critical dimensions regarding this but also it can play into where the fork is truly settled in the stroke.

    The bottom out, while severe is not bad, it is "G"out followed by a step up. The most difficult terrain item for a tandem on a flowing trail in my opinion.

    With both springs removed, will the fork bottom on the internal bottoming cone or are the seals hitting the bottom of the lower triple clamp? Reference the manual link you posted, pages 9,10. They mention the notch in the tube and max headtube stuff.

    I'm suspecting the fork is too long and causing some of the concerns.. but the forks action looked pretty good.

    PK
    There is 137mm from the top of the lowers to the bottom triple clamp. (I had thought I had shortened to 130....its growing!?)

    Marzocchi was good enough to put "Min" and "Max" marking on the tubes for the lower triple clamp, and I am honoring the "Min" mark. With the springs out and the fork bottomed there is very little free space between the lower and the clamp, but they don't touch.

    There is about 145mm between the upper and lower clamps.

    I'll start a new thread for the video of the rear shock. The back end is performing less well.
    Last edited by reamer41; 01-16-2011 at 12:35 PM.

  14. #89
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    Paul,

    A quick question for you: We were out the other day on one of our local oft ridden trails. On one section of rough descent the fork bottomed hard, with a bang, where it usually doesn't. It was hard! For a moment I worried about structural failure, or something. It seemed OK for the rest of the ride and there is no external evidence of anything wrong.

    Could that type thing be caused by too low oil level? Previous bumps stirred things up and left me with no compression damping? Whatever its cause, it was very unsettling!

    --Charlie

  15. #90
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    Bringing this back to the top for some added stuff.

    #1 If you run a Fox fork or any brand that has fluid for the lower tubes isolated from the damping fluid (closed cartridge forks), keep the lower fork lube replenished. This can be a big factor in how the fork feels to the rider and how it follows terrain.


    #2 Curious how many tandems still have ATC forks, and if so, is there an interest into some simple and inexpensive mods to up the performance. Some of the items have already been posted, but this past week I converted our Fandango fork to a "wet" fork. No more greasing. I made some other mods, so individual mods can not be evaluated. IMHO the fork is another step up from where it was. If no one is running these forks I won't bother.

    #3 Those teams attending AORTA 2011, are there any specific fork or shock issues we need to focus the informal suspension discussion about? The discussion will be geared towards setup. I'm asking in case I need to pillage a manufacturers site for cutaways or other specific details I may not have committed to memory.

    PK

  16. #91
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    Hi Paul,
    Anything with the WB Magic 100 T and the Fox RP23 would be helpful. I know you don't own the WB fork but it is probably the fork that Alex sells the most of. From setup, tuning, modification and service for both of those.
    Ed Gifford
    the Snot Rocket tandem

  17. #92
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    I guess we're the only Fox Vanilla fork out there?
    ~live vicariously through yourself~

  18. #93
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    I need to ask again about the ATC fork, is there any interest in them?

    I know others run them having seen two at AORTA 2011. Not sure if the fork warrants the work in other folks eyes.

    I am tempted to have some good springs wound to save weight and get better action from the fork. I don't really want to go it alone but may.

    Any interest or stick a fork in 'em, they're done.

    PK

  19. #94
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    Hey PMK,

    Who do you (or have you ever) used for a custom wound fork spring? I was thinking I would like to get a touch stiffer spring for our tandem since we're running the firmest available.

    Thanks!

  20. #95
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    Quote Originally Posted by Rida29r View Post
    I guess we're the only Fox Vanilla fork out there?
    From doing homework on your profile...seems to indicate Ellsworth Witness.

    There are a few Vanilla versions over the years, I'm optimistic you are running a 36 version.

    Should be fine, though technically not an "approved" tandem fork. Depending upon the payload weight and how crazy the stoker allows the captain to be will sort out not only its durability but also if additional efforts need to go into tuning it.

    I'd guess you at least got the travel shortened to something to allow the bike to steer, and firmed up the spring to keep your toes on your feet.

    Being serious, how does it work for you two, what is the setup, and if it's not so good, why?

    PK

  21. #96
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    Quote Originally Posted by Team Fubar Rider View Post
    Hey PMK,

    Who do you (or have you ever) used for a custom wound fork spring? I was thinking I would like to get a touch stiffer spring for our tandem since we're running the firmest available.

    Thanks!
    I have spoken with Cannonracecraft. You will need to know your criteria for them to wind to. Mainly OD, Free Length, Minimum Length, and Rate. Also if the ends are special that may need to be noted.

    http://www.cannonracecraft.com/

    My last discussion with them was a tapered profile small diameter heavy spring for a Moto fork on our Cannondale. I never had them wind it as I stuffed old Judy bumpers that were cut to a smaller OD in the lathe, down the inside Dia of the spring.

    That worked real good for adding rate and progression.

    Your other option, and I constantly research what I have on hand plus catalogs is to find a spring to set inside the original spring, but with the wind in the opposite direction.

    PK

  22. #97
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    Hello Paul and all,

    We have a 2006 Marz 66SL (dual air). I've noticed recently that the negative chamber has been leaking pressure over short periods of time and when disconnecting the pump from the mini Shrader port there is an abnormal spray of fork oil (it is minor as to amount, but six months ago and prior there had been none).

    Research on MTBR and other sources has indicated two o-rings that are known to fail over time and would present as the oil-intruding-into-the-negative-pressure-resevoir issue. However, Marz USA does not have any o-rings available, nor do they have the left-leg cartridge available.

    With lower/no negative pressure the fork is much more active than prior. I don't know the long-term consequences of running with low/no neg pressure, or if it is such that a new fork should be on the horizon.

    There are a few 66's out there - anyone have experience?

    Thanks

  23. #98
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    Quote Originally Posted by Okayfine View Post
    Hello Paul and all,

    We have a 2006 Marz 66SL (dual air). I've noticed recently that the negative chamber has been leaking pressure over short periods of time and when disconnecting the pump from the mini Shrader port there is an abnormal spray of fork oil (it is minor as to amount, but six months ago and prior there had been none).

    Research on MTBR and other sources has indicated two o-rings that are known to fail over time and would present as the oil-intruding-into-the-negative-pressure-resevoir issue. However, Marz USA does not have any o-rings available, nor do they have the left-leg cartridge available.

    With lower/no negative pressure the fork is much more active than prior. I don't know the long-term consequences of running with low/no neg pressure, or if it is such that a new fork should be on the horizon.

    There are a few 66's out there - anyone have experience?

    Thanks
    Bummer about the fork. I own a Marzocchi on my Turner and it has the similar setup with negative and positive air chambers.

    You've no doubt read what could be found. Somewhat of a common problem. Some say just dis-assemble, clean, service and ride.

    It probably should get new seals.

    As for riding without negative air, it will be a long fork and my tend to top out a lot more,. I don't know if there is a bumper also inside it to prevent damage.

    As for a new fork, much of that is how worn and scratched the upper legs are. If you can be comfortable taking it apart, the "O"rings can be matched up at a hydraulic shop, worse case is ordering some from McMaster or other supplier.

    Sorry I can't offer more, I see you are also planning a trip. Makes sending it here or elsewhere tough.

    PK

  24. #99
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    We rode it yesterday. A somewhat unpleasant experience due to the topping-out as you indicated. There doesn't seem to be a bumper, given the mechanical clacking which at times was semi-violent. There was also more sticktion, which follows given what Marz says in their service manual regarding the negative air chamber's function. It may have also been a function of the increase positive air I put in to compensate for the soggyness, so there is a bit of experimentation.

    I can change the oil and seals and I'll see what the o-rings look like - have to make some soft jaws to hold the cartridge shaft. I never found specs for ID or thickness/OD, and the Marz guy didn't have any. My experience in the automotive world, a little excess thickness means things don't fit any more.

    Thanks, Paul!

  25. #100
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    An update - I am now in possession of 99 each of the round profile and the square profile o-rings used in the Marz 66SL Doppio cartridges. Had to buy in batches of 100. I pulled the Doppio apart and exchanged the o-rings. Used parts didn't look noticably worn.

    However, the new parts are holding pressure and not pulling in oil.

    I went ahead and changed out the oil seals since I had a spare set and it was more or less time. Which then presented a new problem of not holding positive pressure. Seems the genuine Marz seals are slightly undersize - they needed almost no pressure to install, and leak (alternatively) air or oil. I have another set of Enduro seals coming in the post as I keep one set on hand...but ended up digging out the "old" seals from the trash and reinstalling them - they required more pressure to install than the "new" ones. Hoping for positive pressure so we can ride this weekend. Enduro seals won't be in until Wednesday.

    On the flip side, I'm pretty quick R&Ring the fork seals and cartridges...

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