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  1. #1
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    Suspension Fork Experience - What's Working? What's Not?

    Recently I have had a few converstions about suspension forks on a tandem. I would be interested to hear people's experience with their existing set up.

    1. What fork make/model and what frame make/model?
    1a. single or dual crown
    1b. lock out?
    1c. axle type 20mm thru? 9mm QR?
    2. Team weight?
    3. Type of riding.
    4. Any feedback regarding performance, maintenance etc. (positive or negative).

    I think this type of information on this forum would be extremely valuable.

    Also, feel free to add anything that I missed. And don't be bashfull telling us if you are running a "non-tandem rated" fork. This is an informal poll - you can always hide behind your screen name...

    Thanks!
    Last edited by ds2199; 07-09-2010 at 08:08 PM.

  2. #2
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    I guess I'll start

    1. 2009 Marzochi 55ATA on a Ventana ECDM (full suspension)
    1a. single crown
    1b. has "lock out"
    1c. 20 mm thru axle
    2. aprox 270
    3. we ride jeep roads, twisty singletrack, rocky trails (just about anything that I'd ride on my single bike - but no BIG drop offs).
    4. fork has worked out well so far despite unfavorable reviews on Marz forks. We have about 2500 miles on the fork (seals replaced this past spring). 20mm axle works very well and is actually a form of quick release.

    For as much bad press as I have received on the Marz forks, I have been pleasantly surprised with the performance of the fork. My local shops are all big Fox fans.

  3. #3
    Ride, Rinse, Repeat
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    Fox

    A great Thread Idea. We are definitely in the "non-approved" bunch...

    1- Fox 36 Talas RLC 160mm on Ellsworth Witness
    1a - Single Crown
    1b - Lock out - yes (used SELDOM - Only for LONG road sections)
    1c - 20 mm QR
    1d - 203mm Disc rotors/Hope Mono M6 calipers
    2 - ~300 Team/50 lb bike
    3 - Mostly Colorado Singletrack, up to "moderately" technical, PLENTY of Rocks, lots of tight/twisty.
    4- Performs REALLY well. Stiff and tracks well. Think a 20mm thru axle is a requirement on a tandem. Replaced a Rock Shox Pike 454 (32mm stanchions..) and the Fox was a HUGE improvement in steering response and precision. A huge confidence boost. Good adjustability, the low speed damping adjustment REALLY helps keep the wallowing from the big bike under control. Holding up fine so far. 2 seasons on it, not a huge amount of hours on it, getting due to have seals done, but holding air pressure well, no oil leaks so far.

    Been VERY happy with the Fox, and have NO complaints.

    We have had the chance to ride a Mazzochi 55ATA on a friends Ellsworth Witness back to back with our Witness/Fox setup. The Marzzochi seems a bit stiffer than the Fox, noticeably more tracking precision. A gazzillion adjustments. I'll try to get him to post up...

  4. #4
    PMK
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    I'll post details later about what we ride...

    To help others, why not also add your setup parameters if possible. Compression setting, rebound, spring or or air pressure, type terrain and team weight, chassis would be nice help also.

    Just a thought.

    PK

  5. #5
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    1- Old Marzocchi DJ
    1a - Single Crown
    1b - No lock out (Wish we had it)
    1c - 9mm QR
    1d - 203mm Disc rotors/Hope Enduro 4 pistons
    2 - ~350 Team/50 lb bike
    3 - Mainly just Iowa singletrack right now, we have done a small amount of 1-2 foot drops, stairs etc.
    4- Good fork, much better ride then a rigid fork. Wish it had a lockout though, while standing it bobs like crazy.

  6. #6
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    Quote Originally Posted by DaleTR
    4- Performs REALLY well. Stiff and tracks well. Think a 20mm thru axle is a requirement on a tandem. Replaced a Rock Shox Pike 454 (32mm stanchions..) and the Fox was a HUGE improvement in steering response and precision. A huge confidence boost. Good adjustability, the low speed damping adjustment REALLY helps keep the wallowing from the big bike under control. Holding up fine so far. 2 seasons on it, not a huge amount of hours on it, getting due to have seals done, but holding air pressure well, no oil leaks so far.
    I was planning on building a hardtail tandem using a Pike 454 that I already have. Could you explain a little more why the TALAS is better?
    May the air be filled with tires!

  7. #7
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    Im not sure about the talas, but I know the Pike is not "tandem rated"

  8. #8
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    Quote Originally Posted by Mr.SBC
    Im not sure about the talas, but I know the Pike is not "tandem rated"
    I don't believe any Rock Shox or Fox fork is tandem rated. In fact, they specifically say not to use their forks on tandems.

    "FOX bicycle products are not designed or manufactured for use on any motorized bicycle, motorized cycle or motorized vehicle or for use on any vehicles carrying more than one operator/rider. Any such use constitutes misuse, which may result in serious injury, death or property damage, and will void all FOX warranties."
    May the air be filled with tires!

  9. #9
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    I am very interested to continue to hear ALL experiences with suspension tandem forks.

    The whole point of this topic is to hear what is working and what is not. I know for a fact that many people use components that ARE NOT tandem rated. Many of them ARE up to the task. I realize that many component manufacturers do not care enough about the niche that is tandems let alone mountain bike tandems.

    I am not endorsing nor encouraging the use of Non-tandem rated items. I AM interested to real world experience (tandem rated or otherwise).

    Please continue to share - Thanks!!!

    I suppose someone like Alex will chime in at some point and let people know the list of tandem rated forks (I think it may be a pretty short list).

  10. #10
    Ride, Rinse, Repeat
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    Pike

    Quote Originally Posted by Blaster1200
    I was planning on building a hardtail tandem using a Pike 454 that I already have. Could you explain a little more why the TALAS is better?
    Purely Stiffness & steering precision. The Pike (even with the 20mm..), while reasonable, tended to flex and "wander" a LOT more than the 36 TALAS under hard cornering or banging in the rocks. Until I made the switch I was pretty happy with the Pike, but was just looking for a bit less flex, and figured the bigger stanchions and beefier crown would help, and it made even more of a difference than I imagined.

    The TALAS seems to give more tuning options as well. even with an "extra Stiff" spring in the Pike, the sag and low speed compression was more than I liked, probably contributing to the feeling of flex...

    I think the Pike would be fine if your riding tends to the less rocky or less twisty side, but was getting overmatched on tight & rocky stuff.

  11. #11
    MTB Tandem Nut
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    Quote Originally Posted by ds2199

    I suppose someone like Alex will chime in at some point and let people know the list of tandem rated forks (I think it may be a pretty short list).
    I was going to stay out of this one in the hopes that folks would provide more info without fear of the "fork police" making comments about various forks being approved for tandem use. However, since you mention it, here's the (short) list of forks still in production:
    White Brothers Magic 100T (dual crown) and Groove 180 & 200.
    ATC Racing T-5
    Marzocchi 66, 55, DJ and 4X.
    Rockshox had no particular concerns with structural integrity of their Boxxer forks, but would not warrant the internals under tandem loads. Some will recall this fork was spec'd on Cannondale tandems for a couple of years.
    Risse Trixxy & Champ
    Manitou Circus (DJ style) and Dorado.
    Sad, ain't it?
    Last edited by TandemNut; 07-13-2010 at 05:27 AM.
    MTB Tandems Inc.
    678-445-0711
    www.MTBTandems.com

  12. #12
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    1. Cannondale Moto Fork w/red springs
    1a. dual crown
    1b. No lock out
    1c. 9mm QR

    2. Team weight...about 325 LBS
    3. Type of riding....Single-track and forest roads lots of rocky spots
    4. I like this fork but its only one I've tried on on our Cannondale so I don't know any better.
    its gotten us down some very rocky downhills safe and sound
    as far as maintenance its very easy to rebuild although finding parts that's much harder (anyone have brown springs...or feed back on red vs brown springs?)

    ds2199, thanks for this post should be very helpful
    also...could you guys add what forks you used in the past and how they compare to your current setup?

    Thanks
    Darwin was an Optimist

  13. #13
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    1. 2010 Fox TALAS 36 RC2 (FIT cartridge) on a Ventana ECDM

    - Single crown, 1.5" steerer tube (straight not tapered)
    - No lock-out. Not needed for seated climbing, but very hard to coordinate standing climbs because of the fork bob. We do stand individually and find that acceptable.
    - 20mm thru-axle (love it)
    - 203mm disc rotors, Avid BB7 brakes

    2. 270 lb team weight + 50ish lb bike (never weighed the bike)

    3. Aggressive XC, rocky singletrack, desert trails, fireroads. Just about anything without big drops and tight switchbacks (or we'll walk those). Usually long climbs with long descents (average ride has 5000'+ ascent/descent). I'll ride more technical trails on the tandem than I would on my single because of the tandem's stability.

    4. I absolutely love this fork. Travel is adjustable with the turn of a knob between 4", 5", and 6" (100-130-160mm). For almost all riding we'll use the 5" travel. If it's a long smooth climb I'll drop it to 4". If it's really nasty I'll up it to 6" but handling can get a little sluggish like that. Very stiff, confidence-inspiring fork because of the 36mm stanchions, 20mm thru-axle, and 1.5" steerer tube. Maintenance heavy, though, need to service dust wipers every 15-30 hours and change oil every 100 hours (6 months for us).

    Sometimes I'll start to think this fork isn't doing much because I never feel it move. Then I'll ride my single bike (Reba 29er) and it's a world of difference. The TALAS just soaks up everything. Deep ruts, rocks, roots... we just float over them. Very happy with this purchase.

    Thanks for this topic. This is our first suspension tandem so I have no other forks to compare.

  14. #14
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    We are pretty happy with the White Bros Magic 100T. Bike: 50lbs-ish, us: 270lbs, tools,water and etc: 20lbs?
    We are running a Fandango 29er hardtail, fork is at 50-60 psi. I would say we ride pretty aggressively. I like to take chances on the trail, but I am not comfortable doing that AND running non-tandem rated forks..Just my 2 cents.

  15. #15
    Schipperkes are cool.
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    Maverick DUC32 is tandem rated if correctly setup. I have a client that has 2 tandems with DUC on the front; Ventana 26" and Eriksen 29" hardtail. I have a bit of time setting them up and he will not look towards any other fork.
    Quote Originally Posted by mikesee
    Better suited to non-aggressive 125# gals named Russell.
    I ride so slow, your Garmin will shut off.

  16. #16
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    Quote Originally Posted by banks
    Maverick DUC32 is tandem rated if correctly setup. I have a client that has 2 tandems with DUC on the front; Ventana 26" and Eriksen 29" hardtail. I have a bit of time setting them up and he will not look towards any other fork.
    I've heard good things about the DUC 32 - too bad it is out of production for now. There's been rumors of a carbon version but that's going on almost 2 years...

    Damn... Ventana 26 AND Eriksen 29?... is that Chuck and Karla?

  17. #17
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    My brother and I ride a Scott aluminum hard tail here in CO ( just not enough as we are oppisite sides of the state. We have a Rock Shox Argyle single crown w/ 20 mm. It has only 4" travel but tracks well. It has steel stanchions and special springs. Works well as we are 360# of riders plus gear. we also use Avid code brakes that are amazing. The Fox 36 should be a great fork w/ the big stanchions and air assist, would probably use the Van model w/ coil spring. 20 MM is the only way on mtn tandem unless you are pretty light riders.

  18. #18
    PMK
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    Several bikes to comment about. 380 pound team.

    1998 Cannondale MT 3000. Moto fork, 100mm with 9mm QR axle. Non disc brake version. Fork has oem valving, but has been modified as follows. Fork boots from lefties, Ohlins suspension fluid, coil spring is oem but the elastomer has had a section of Judy elastomer machined to fit the upper spring end.

    Preload run full firm, fork work very well, minimal if any flex is noticed, turning to steering stop allows almost 90 degrees of motion per side.

    Fork requires special tools to work on it easily. Normal stuff gets accomplished, rollers lubed with Phil Wood oil, cartridge fluid replenished as needed. Had one lower triple clamp crack at the bolt hole, no failure, blended away the crack and check it frequently. The clamp is a documented problem from long ago. The on the fly adjustable rebound is sometimes utilized for different terrain.

    Our 2001 MT800, I installed a Manitou Sherman single crown with 20mm axle, travel is adjustable (110mm / 150mm), but we always ran it in 110mm setting, 150 was to slack on the headtube angle. Changes made, swapped spring to extra firm, replaced damper fluid to 10 wt Motorex from oem 5 wt Motorex. Fork worked well but was used only for less than fifty miles of use, some jeep road some technical single track. Not a bad fork, but I would personally like more ramp up or progression for better mid stroke / bottoming control.

    ATC, with 20mm and Avid BB7, 100mm of travel. We have ridden one while installed on our MT3000, double red springs, as delivered it had no amount of spring preload, added 10mm (?) of preload, this held the front up much better. The fork was a bit under damped for us, replaced damper fluid to 20wt. Good turning radius. The lack of external adjustments was acceptable, but made on the trail tweaks tough. Once dialed in, this was an obvious replacement for the Moto when needed. This fork was tested on technical singletrack, hardpack, sand, and other varied terrain.

    We are now re outfitting our "squadron", one of our latest rides is an ECDM, it too has the ATC 100mm fork with a 20mm axle, Louise (210mm?) brake. Like the other ATC we tested, steering precision is very good, turning radius also. I need open this thing up, but speculate it has a pair of red springs (had at least one when I checked the tire to triple clamp clearance with the fork cap removed). Preload currently installed is about 8mm. This fork could use a bit more damping, it will likely also see 20wt fluid as the other fork did.

    Our Fandango 29'r is here and I'm working to get it built, it too will have the ATC fork with 20mm axle and an Avid BB7 203mm disc. We have not ridden at great length any other forks on a tandem.

    I have installed a Fox40 onto the MT3000, planning to shorten the stroke to 100mm, unfortunately the triple clamp / lower leg offsets did not allow ample turning radius for where we ride.

    I also have a Marzocchi drop off triple, modified from 170mm to 110mm of travel. I did install this onto the MT800 but other parts of the bike were not finished, the Manitou was fitted since the forks steerer tube was a more proper length. This fork has decent turning radius, is easy to work on, is spring with air over oil, open style damper with internally adjustable rebound. I believe this fork should work decent, provided the rigidity is ample for good steering precision, but again I have not run it.

    The present focus will be on further dialing in the ATC's, since this is our current setups for the most part.

    In my opinion, one of the greater challenges is finding proper springs for these forks at the loads we run them. Also, some of the forks, based on single bike test, do not have much if any progression to the spring via an air column. Obviously flex is a concern, also, but is always a trade off against weight, unless you run and air spring fork setup.For some teams this may be very important.

    PK

  19. #19
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    We've been using a Rock Shox Argyle 318 (their DJ fork) on our C'dale tandem for about a year and a half with good success. I think for any teams over 300-325 lbs. it might be under sprung even with the extra firm spring in it. We're right at 300 lbs. and it is fine, but I know if it is much more, it won't be without some custom springs.

    The thing about the RS Argyle is it has steel stanchions (stiffer than the alu ones on the Pike/Revelation/etc.) a 20mm Maxxle, and a lock out. If I did it over, I'd probably go with the 409, that is an air sprung fork. for more adjustability.

  20. #20
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    Forks

    Clan McKim: Team weight 300lbs

    1998? - The first fork we tried was a "Bad Betty Bombshell". It was on a Da Vinci tandem we demoed. To be fair, it was set up for a different team, but it did not move much at all. It looked massive and cool but not so functional.

    2001 - Next came a 100mm travel Cannondale Moto (tandem version). It had red springsand quick release. I looked for brown ones but was told that not all tandem springs were actually brown...gave up and stuffed some extra elastomers inside the spring to firm it up. The fork worked really well, handling some serious abuse with minimal deflection or flex. We blew up a retaining clip and sprayed little roller bearings all over the inside of the fork. Fortunately we could still get the fork rebuilt by Cannondale. It started with hydraulic rim brakes and survived a conversion to discs. It now is in use by my in-laws and family as a "dirt-road" tandem, and still works well.

    2006 - With our new El Conq we got an ATC fork. It started at 100mm but I ran it most at 125mm. This fork drove me nuts. From day one it had major sticking problems, eventually getting bad enough that it would "lockout" from stiction during a ride. I tried every combination of tightening bots/loosening bolts/lubing/cleaning that I could think of. I even sent it back for a full rebuild by ATC (got a story about the sticking being due to the color of the lower legs, not kidding..). This was a 20mm thru axle and rode very confidently - very stable and solid, it just didn't move right. I fixed it as best I could and sold it since my stoker was tired of hearing me b**ch about it.

    2008 - Marzocchi Jr. T. The first big ride we did with this fork was Monarch Crest in Colorado. I couldn't stop laughing. Every time I hit a bump/drop/roller I broke out in joyful whooping. This fork is huge 170mm travel, 20mm thru axle and very smooth. It was way too soft out of the box, but the addition of the air preload caps quickly fixed that. It could probably use a servicing and maybe a touch heavier oil to increase damping. It is amazingly supple, but will bob quite a bit on hard flat peddling. Honestly I want about a 140mm fork, but in the Tandem rated world there is not much and out here in Grand Junction I would rather use too much fork rather than too little. The folks at White Bros told me they could modify something for me, but I would need a job first.

    2010 - To be fair to ATC, I test road a Ventana at AORTA that was specced with an ATC. I was really curious as to how a different fork would ride. It was much better. Some very slight sticking, but nothing substantial. The Ventana with the ATC felt "zippier" than the one with the Marzocchi.

  21. #21
    Old school BMXer
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    Along the lines of this discussion, what would you all consider as the ideal amount of fork travel on a rigid rear tandem, and why?
    May the air be filled with tires!

  22. #22
    Long Live Long Rides
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    travel

    I think it will vary quite a bit depending on riding style and terrain. For us I really think 140-150mm would be best, but I've never tried a fork with that travel so I'm just guessing. 100mm is the minimum I would try.

  23. #23
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    Quote Originally Posted by Trails4Two
    I think it will vary quite a bit depending on riding style and terrain. For us I really think 140-150mm would be best, but I've never tried a fork with that travel so I'm just guessing. 100mm is the minimum I would try.
    Oh, yeah...riding style...It really depends on what my wife will tolerate. We don't have a tandem yet, but I'm working on that, so we don't have any experience on a tandem. I race DH and BMX at an expert level (even at age 41), but my wife is a little more conservative, although she does ride BMX and DH (yes, even at Whistler!). So that means her comfort level will be the limit of technical terrain and speed. We may later move to a full-suspension frame. For her comfort, I already did pick up a Thudbuster seatpost.

    As mentioned above, I was planning on using a Pike, but set at 125. I also have a Fox 36 Float I can use. The reason I need to pick the travel is that I want to design the frame around a particular travel. Of course, I can deviate from that a bit, but I want to at least have a target in mind.

    This has been an informative thread! Thanks to all who've replied!
    May the air be filled with tires!

  24. #24
    Long Live Long Rides
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    I'd pick a general 125mm travel to build the frame around. If you need more travel, remember that with a longer wheelbase more travel has less effect on head angle than on a short bike.

  25. #25
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    Quote Originally Posted by Blaster1200
    Oh, yeah...riding style...It really depends on what my wife will tolerate. We don't have a tandem yet, but I'm working on that, so we don't have any experience on a tandem. I race DH and BMX at an expert level (even at age 41), but my wife is a little more conservative, although she does ride BMX and DH (yes, even at Whistler!). So that means her comfort level will be the limit of technical terrain and speed. We may later move to a full-suspension frame. For her comfort, I already did pick up a Thudbuster seatpost.

    As mentioned above, I was planning on using a Pike, but set at 125. I also have a Fox 36 Float I can use. The reason I need to pick the travel is that I want to design the frame around a particular travel. Of course, I can deviate from that a bit, but I want to at least have a target in mind.

    This has been an informative thread! Thanks to all who've replied!
    I'd use the 36 Float, and probably all of the travel or reduced to 130-140mm. I am not sure how much tandem experience you have, but with your background and a trusting wife you could really have some fun with the stability of the tandem.

    We run a 36 TALAS, 100mm = quicker handling, not as plush, 130mm = happy medium, 160mm = sluggish steering, but float over everything. Other than steering, I don't notice any difference in overall bike geometry, compared to a single bike where an adjustable fork can totally change how the bike feels.

  26. #26
    PMK
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    Quote Originally Posted by drdoak
    1. 2010 Fox TALAS 36 RC2 (FIT cartridge) on a Ventana ECDM

    - Single crown, 1.5" steerer tube (straight not tapered)
    - No lock-out. Not needed for seated climbing, but very hard to coordinate standing climbs because of the fork bob. We do stand individually and find that acceptable.
    - 20mm thru-axle (love it)
    - 203mm disc rotors, Avid BB7 brakes

    2. 270 lb team weight + 50ish lb bike (never weighed the bike)

    3. Aggressive XC, rocky singletrack, desert trails, fireroads. Just about anything without big drops and tight switchbacks (or we'll walk those). Usually long climbs with long descents (average ride has 5000'+ ascent/descent). I'll ride more technical trails on the tandem than I would on my single because of the tandem's stability.

    4. I absolutely love this fork. Travel is adjustable with the turn of a knob between 4", 5", and 6" (100-130-160mm). For almost all riding we'll use the 5" travel. If it's a long smooth climb I'll drop it to 4". If it's really nasty I'll up it to 6" but handling can get a little sluggish like that. Very stiff, confidence-inspiring fork because of the 36mm stanchions, 20mm thru-axle, and 1.5" steerer tube. Maintenance heavy, though, need to service dust wipers every 15-30 hours and change oil every 100 hours (6 months for us).

    Sometimes I'll start to think this fork isn't doing much because I never feel it move. Then I'll ride my single bike (Reba 29er) and it's a world of difference. The TALAS just soaks up everything. Deep ruts, rocks, roots... we just float over them. Very happy with this purchase.

    Thanks for this topic. This is our first suspension tandem so I have no other forks to compare.
    Have you posted a photo of this bike overall and maybe with some detail photos somewhere on the net? I would like to see some photos of it.

    Thanks
    PK

  27. #27
    PMK
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    With some rides on our ATC forks on both the Fandango and ECDM, I'm learning what I like and dislike about these forks. Consider also I spent some miles on a loaner fork that was installed on our MT3000.

    As mentioned, we now own two ATC forks, one installed on our Fandango 29r hardtail and the other on our ECDM later model series with the rear shock upright and parallel to the seatube.

    On both bikes we run 20mm axles.

    One bike has Magura Louise discs while the 29r uses BB7's.

    What is good about these forks…

    As I mentioned in a previous post they are very good in steering precision and not flexing. This is probably based on the fact of them having large diameter tubes.

    No flex is noticed while rolling, this includes brake forces trying to bend the fork aft, or twisting flex from steering inputs or on a result of deflections.

    The fork has merit in its modular machined construction.

    The design is a dry type fork, with no oil bath for the telescopic tubes. These are lubricated via grease ports.

    Seals are easily cleaned on account of the sealheads being threaded onto the outer tubes.

    Bushings are a finger fit and requiring no special tools.

    Fork travel settings can be varied by spacer location changes from a top out or negative position to positive positions, or if additional travel can be utilized, spacers may be left out. This is also how axle to crown dimensions can be dialed in to obtain manufacturer head angle and trail dimensions.

    Being a dry fork design, major fork leaks are minimized to non existent. Also the damper cartridge is on the side opposite the disc, so even if it were to leak, the disc should remain uncontaminated from leaking fluid.

    Things to not like about these forks…

    First off, many folks have complaints about the forks being notchy as they move through the stroke.

    Some have complained about knocking sounds during fork movements.

    From experience, I do not like servicing the fluid in the damper. Having worked on motocross suspension setups since the mid 70’s, I still do not have enough experience to easily bleed one of these dampers to my satisfaction unless I modify the damper.

    The triple clamp design is not conducive to proper torques needed to secure the fork tubes.

    The fork bridge mounting, like the triple clamp pinch bolts is not proper for good clamping to the outer tubes.

    By design, the bottoming cushion is placed to impact the damper seal with no support or protection to the seal.

    A minor concern is no easily removed front wheel.

    For some, the lack of compression, rebound, lockout or on the fly travel is a concern.

    So there you have some thoughts on good and bad. Thing is I still do not object to these forks. Having been around the moto end of stuff long enough, I don’t get worked up on account of dialing stuff in. For me these forks are no different.

    So, our team weight is 370 ish plus camelbacks and helmets. We ride a lot of stupid drops, really tight trails, palmetto roots and sometimes hardpack ruts, plus lots of sand. Speeds range from crawling and plonking to decent flat ground cruising, and when possible, long descents like those at AORTA.

    Neither of the two forks we currently own were great as delivered. They were ok and ridable but nothing to rival Ohlins. This past weekend had me spend some time working out some of the major concerns.

    FWIW, I had previously modified a damper for easy consistent bleeds, so this chapter is closed.

    Simple damping changes are made via fluid viscosity changes, and easy bleeds make this a no brainer, provided you not on the damper or your setup notes what fluid you installed. By now most of the world is familiar with Peter Verones fluid chart. This is a huge help when comparing fluids, whether for your tandem, single or motocross / harescramble ride.

    Scroll down this page to compare fluids.

    http://www.pvdwiki.com/index.php?title=Suspension_Fluid

    Be forewarned that not all fluids have good lubrication properties. Many folks buy fluid based on its VI ratings. Typically, I have found that fluid with high VI’s, tend to have less slippery feel on the sliding surfaces. Some fluids are just crap, and others are excellent. FWIW, for Silkolene Pro RSF is a great fluid in demanding apps, but is not good for being slippery. Guess what Fox now uses? Torco stuff works very well. Also, if the viscosity is proper my favorite is Mobil1 ATF, trust me it works very well and has for years in my KTM race bike.

    My notes show that the ATC forks prefer heavier fluids to obtain damping. 20 weight Bel-Ray was on the shelf and has been used with good results. These dampers are very basic and use no amount of shim stacks like the more sophisticated counter parts. This doesn’t make it bad, just different, and somewhat easier to get good settings. Those of us that have time on 70 and early 80 motocross machines rode on damper rod forks, these were simple in operation and maintenance, but performed very well in many bikes. Consider the 81 Maico 490, which still works well for non stadium type tracks. Shim type dampers are great if you have shims AND know how to make good shim changes. This is its own book and won’t be discussed here.

    Now to focus on the mechanics of the sliding tubes…

    If you have time to work on your fork, I suggest you remove the wheel with the bike supported, remove the springs, and remove the damper rod nut and spring plunger nut, both of these are located in the forks outer tube lower fitting behind the axle. This will allow checking the tube movements with no outside force applied. Also, remove the four cap screws securing the fork brace.

    In this setup, slide the forks telescopically, do they move freely? Don’t let the damper foul you checks on the right side leg. If the forks feel notchy, loosen and remove the fork brace mount pinch bolts. Did the fork get better?

    These were checks I made to our forks repeatedly until I was able to make the movement smooth.

    To gain smoothness, these are the things I did to free up the forks and why.

    I decided the fork brace mounts and triple clamp pinch bolts can not secure the tubes tightly without distorting the clamps to a shape that is no longer round and true. Basically, the pinch bolts begin to cant the clamp edge into the tube causing distortion. If you prevent the distortion with less torque on the bolts, slippage will occur. My remedy for this was to install NAS 43 DD spacers of the proper thickness in the gaps of the clamping surfaces. This allowed full torque on the fasteners with no distortion since the spacer was now holding the pinching surfaces parallel. I checked the clamps holding ability on the tubes to ensure no slippage. This included checks for twisting easily by hand force, and exerting bottoming forces by hand to see if the tubes slipped. These were also monitored during the first ride as a double check. FWIW, we did have tubes slip several times prior to this mod, and this was on account of not being able to get enough clamping pressure on the tube prior to the clamp distorting and going out of round.

    In regards to the clamp up for the fork brace mounts, the ECDM was fine on the lower tubes external surface. The Fandango however, with spacers installed a very exact zero / zero slip fit. This would not work since the clamps would not hold the brace to tube tightly. I made shims for each clamping surface. These shims were nothing more than aluminum tape, cut 1” wide with scissors. The tape was wrapped and adhered one layer thick onto the outer tube, in the clamp location. The tapes split line was positioned 180 from the clamps pinch opening. The tape allowed excellent clamping of the mount to tube with full torque on the pinch bolts.

    Next the tubes were checked for sliding action individually. Each tube was extended and compressed, checking for tight spots or poor quality in the movement. Fortunately, there was no additional work need for good movement.

    I did check the lower bushings to ensure proper fit on the tube. To accomplish this, I ensured that the bushing ends where split had clearance, thus allowing the bushing to be seated onto the tube land 100%.

    Prior to accomplishing a final install on the foot nuts for the damper and spring plunger, the damper was checked for smooth movement. Also, any travel adjustment were made. It was noted that the ECDM at full bottom out would have the dust seals hit the lower triple clamp with full uncushioned force. Not good. To prevent this, the bottoming cushion was extended by using a Thudbuster gray elastomer. This will give a more fluid bottoming control. I could have installed a rigid spacer but opted not to. The ECDM travel was maintained at slightly over 100mms while keeping Sherwoods spec for axle to crown.
    In regards to the Fandango, I found I could increase travel, and removed some of the rigid bottoming spacers. Both bikes no longer run fork boots.

    The foot nuts were final installed and secured.

    The wheel was positioned and axle secured. What I have found works well for this when tightening the axle clamps is to install the capscrews part way. Then tighten the forward two capscrews on each leg until bottomed and snug. Then snug the rear pair on each leg. I then loosen the forward bolts turn on each bolt. The rears are then made snug plus 1/8 turn. I then go back and tighten the four forward bolts turn. All are then rechecked, adding no more than 1/8 turn if needed.

    Note also, that I prefer to push the fork tubes inward to ensure the hub is secure side to side, prior to any tightening of the axle clamps.

    Focus then heads towards the triple clamps. I installed shorter NAS 43 DD spacers into the pinch slots of the clamps. Again, I ensured that each tube was clamped securely and the tubes were inspected for any slippage during the first ride. No slippagae was noted.

    The sequence I use has me snug the upper clamp bolts with the tubes positioned for selected height above the clamps upper surface. You should never position the forks top cap with the caps sides in the clamping area. You should position the tube so the triple clamp is able to secure the fork cap and gain clamping support by clamping in the caps threaded area.

    So I secure the upper clamp to tube joint first, these are snug plus a little bit. Next I snug the lower clamp to the tube. Again this is initially just snug. All of this assumes the headset is adjusted properly since any headset change will require this to be done again. Additionally, this is based on the triple clamps are not twisted on the steerer tube.

    Go back and tighten all the triple clamp to tube bolts.

    The final alignment and tightening involves the fork brace and it’s clamps. I found it best to gradually bring these bolts to snug, then back off slightly. This allows the mounts to twist freely into proper position, and by having the brace float there is no spreading of drawing of the tubes inward or outward during this sequence. I gradually tighten the bolts, with a final tightening done once I know the brace nor clamps will slip out of alignment. Be careful if you do this since the brace mount pinch bolts have very few threads in the aluminum mount. I plan to use longer fasteners of the same length as the brace mount to prevent stripping the aluminum clamp.

    This all sounds very complicated but is actually very easy to accomplish in a short time. Both of our forks move easily and fluidly. I run no seal saver fork boots, but this is your option. Experience for me has shown that unless they are cleaned faithfully, you will make sandpaper and grind up your forks finish.

    Also, the grease I have been using is a low viscosity product from FORD. I was at the dealer get some parts for our toy hauler and saw this tube of grease. It’s a plastic tube that screwed into my small bicycle grease gun. The grease is blue in color and contains Teflon. Cost was about $6 and for me close to home.

    Cost for the spacers is low. One place listed them as a 10 piece minimum at 35 cents per spacer. I believe they also had a 25 dollar order minimum. For me these were stuff I have easy access to, so free for me.

    So was it worth it. Absolutely!!!!!!!!! I personally like many traits of these ATC forks. I will admit that box stock they fall short. Not many will take the time and effort to make this happen, and I understand why. For us the fork works smooth enough now, with no notchy feeling, that the damper will need a more viscous fluid. The fork is also fully clamped with all the capscrews tight. I believe this added to the forks already rigid structure, but it may be something I want to believe.

    Other things I hope to accomplish include…

    Converting one fork (the Fandangos) to air sprung with external damping / possible lockout.

    Locating anti-friction spring seats to minimize internal binding.

    Anti friction the springs sliding surface against the tubes inner wall.

    Will these forks stay or go, I’m not sure. My current lust is to convert the Fandango 29r to a Fox 36 / 20mm axle setup. As for the ECDM, I hope to buy a Kashima Fox 40 to install on the front. This is something for the future and may not happen, but time will tell.

    PK

  28. #28
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    I run a RockShox Boxxer on our Ventana El Testigo. The Boxxer is a dual crown fork with 20mm dropouts. My wife and I weigh 325lbs as a team.
    I have also ran on our other tandems (another Ventana El Testigo we ran a Marzocchi Shiver, a Ventana El Conquisidor we ran a Hanebrink).
    All the forks work great, although Ive been thinking of replacing the Boxxer with a Fox 40 DH fork, for really no apparent reason other that I really like how Fox forks perform on my single bikes, but the RS's are also really good forks...so it may be a wash.

  29. #29
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    For my style of riding , Norcal dirt w lots of roots+ruts, I'm fully pleased w how my Softride stem w my original rigid fork performs.
    My Bike:
    http://www.oldmountainbikes.com/cgi-....cgi?bike=T136

    Have tried forks on other tandems during group tandem outings, and if I was an extreme tandem descender, I'd consider one of the aforementioned moto forks. Climbing on my bike is a dream, and it never has to be locked out, as the stem functions beautifully w/o penalty of fork pogo.

  30. #30
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    Quote Originally Posted by PMK
    Have you posted a photo of this bike overall and maybe with some detail photos somewhere on the net? I would like to see some photos of it.

    Thanks
    PK
    I don't believe I've posted it before. Here is a link to the album. If you want more specific detailed pics, let me know and I'd be happy to post.

    http://picasaweb.google.com/jeff.dambrun/VentanaECDM#


  31. #31
    PMK
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    Some detail photos of the NAS spacer installation. In the photos, you can see the spacers installed in the pinch area of the lower triple clamp, both left and right sides. Also the other photo shows the spacers installed on the fork brace mounting clamps. The Fandango fork required a shim of aluminum tape to obtain good clamp up of the fork brace clamp. On account of cables and hose, I didn't take photos of the upper triple clamps, they are however typical of the lower triple clamps.

    The spacers allow the triple clamp pinch bolts to reach torque without the triple clamp distorting. The distortion would bind the clamps shape into the tube while placing the bolt at an angle with the head moved away from the tube.

    We have a ride on the Fandango and tonight the ECDM. Both forks have freed up and have minimal stiction and move smoothly. Both forks triple clamps hold the upper tubes tightly with no slipping. Also the fork brace has not slipped.

    The forks have improved enough that I now need to go into the damper and revalve the rebound to slow the extension. The fork action now has no deflection from binding, but rebounds too quickly. The fork will let the wheel follow the ground in compression, with no harshness felt in the bars. The rebound should be minor to cure and will allow me the chance to modify the cartridge body for better consistency.

    The entire process may seem extreme, and yes I believe that these mods should not be needed. The fact is, many suspension assemblies and components, both Moto and MTB are production units that need work to get dialed in. As I already mentioned, it's very common to spend a lot of money or time testing and modding brand new suspension on motocross and woods bikes. By comparison, this has been very little time, easy to remedy, and the gains are more noticeable, cost for the parts if you had to purchase them is less than $10, assuming the vendor has no minimums.

    Hope it helps if you own an ATC.

    I wanted to add, that if you try this with washers instead of NAS spacers, be very careful of the outside diameter dimension. I initially mocked this up using AN960 series airframe washers. I was able to get them installed, however the washers outer edge contacted the fork tubes. Not sure if this would cause a concern or not but I didn't see it as a proper setup and changed it.

    PK
    Attached Thumbnails Attached Thumbnails Suspension Fork Experience - What's Working? What's Not?-copy-img_0682.jpg  

    Suspension Fork Experience - What's Working? What's Not?-copy-img_0684.jpg  

    Suspension Fork Experience - What's Working? What's Not?-copy-img_0686.jpg  


  32. #32
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    Thanks

    Great suspension write-up. It would actually make me consider an ATC again. Alex should hire you to "tune" the ones he gets new!

  33. #33
    PMK
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    Quote Originally Posted by Trails4Two
    Great suspension write-up. It would actually make me consider an ATC again. Alex should hire you to "tune" the ones he gets new!

    FWIW, all suspension can use some personalized or team specific setting changes from oem. Some suspension components just require more than others.

    As an example, the rear damper on my KTM 250 woods bike, is a hybrid I designed and built using parts from several different year dampers. The end result was the bike went from a machine with high speed compression spikes, and a rear damper that was a few mm's too long causing steering / handling issues, to a chassis that is easily dialed in and very ridable if it's not exactly perfect for the day.

    The ATC on the Fandango will be super easy to get the valving correct. It's a hardtail, so there is no front to rear suspension balance to contend with. Just simple tracking, no deflection, compression and rebound.

    The ECDM on the other hand will be a bit more to dial in. Tonight's ride had my wife / stoker understanding rebound damping. We (I) attempted to launch the machine and us by using a logpile as a jump. Nothing high nor steep. Normally we hit this feature around 20 mph. Prior to the fork work, the original RP3 had so little rebound she bounced up and the bike landed, if it even left the ground, nose low on the front wheel. The revalved RP3 works good and is a decent setup but not 100% when needed. With the DHX5.0, she gave good feedback, I instructed her to make certain clicker changes and we had a very balanced and fast setup with the non modified fork. The bike would cross the logpile, the opposite side would be a flat landing, totally uneventful, maybe we got air, but it was small if we did. Tonight's ride had the fork tracking very well, so our speed was up for the pedal effort. When we hit the logpile, the fork rebounded fast enough to have us almost bounce the front wheel over and did launch the bike, landing way too front wheel high. Suffice to say, I was interrogated immediately. I explained rebound damping of the fork and the merits of external adjusters, which led into the Kashima FOX 40 in black.

    I'll revalve the ATC regardless. If I arrive at settings worth posting I'll share them.

    The irony of this ATC stuff though is I'm starting to wonder if I am the only one riding them.

    PK

  34. #34
    MTB Tandem Nut
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    Quote Originally Posted by Trails4Two
    Great suspension write-up. It would actually make me consider an ATC again. Alex should hire you to "tune" the ones he gets new!
    Should a product that's been produced as long as the ATC need this much tuning?
    MTB Tandems Inc.
    678-445-0711
    www.MTBTandems.com

  35. #35
    PMK
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    Quote Originally Posted by TandemNut
    Should a product that's been produced as long as the ATC need this much tuning?
    The obvious answer is no, and honestly, if damping tuning results involve much testing it's Fox40 for the ECDM, and ATC with spares for the Fandango or maybe a FOX36 converted to a 29r fork.

    On the flip side though, the ATC is a torsionally rigid platform well suited for a tandem.

    Sadly the ATC is somewhat dated by todays current damper designs, and the notchy action compounds this.

    Then again, many of the current forks have smooth action but are prone to flex and even failure of internals on account of taking the lightest weight by design possible, or damper designs that are very sophisticated and not serviceable by most folks.

    It would be great to see a torsional deflection vs force graph for the various forks. Then plug in a ride performance rating to see how everything stacks up.

    I haven't given up on these ATC forks yet, if it does come around, it may find all the good traits of rigidity, travel, 29 or 26, and ease of maintenance to be envied. On the lacking end, it will need fluid changes for damping adjustment vs clickers on other brands. Not a bad tradeoff if you can find happiness in the damping and don't require lockout.

    Ironically, I never expected the fork to get this good so easily. About 1 hour per fork so far, and with a good guess on fluid settings, another hour max. Cost has been negligible.

    Time will tell.

    PK
    Last edited by PMK; 08-13-2010 at 05:20 PM.

  36. #36
    PMK
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    Quote Originally Posted by Trails4Two
    Great suspension write-up. It would actually make me consider an ATC again. Alex should hire you to "tune" the ones he gets new!
    Relating to your previous post regarding the idea of a 140mm fork, Marzocchis are typically a very easy conversion.

    I have a double crown Drop Off I had planned to run on the Cannondale. At 170mm it was way to long, and yes a lot of travel compared to the 100mm Moto on it.

    I forget the exact number I clipped it to, but if not right at 110mm something very close to it.

    If done properly, changing travel from oem of 170mm to anything less and back are easily reversible mods.

    PK

  37. #37
    PMK
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    8 more miles on the ECDM with the freed up ATC.

    The fork is better, but it is becoming apparent that rear setup of our ECDM far exceeds the ability of the ATC fork.

    I'll continue to improve these ATC forks I have, keeping updates posted here.

    Over a week ago, I spoke with Alex. We discussed the ATC plus some other forks like the White Brothers 100t, the Groove USD series and even the Risse.

    I would recommend, that unless you NEED a bargain double crown type fork, you will probably be better off to purchase one of the other forks he recommends. I know some folks run non approved tandem forks also, that's fine too in my book, (I know Alex is cringing with good reason) if you have your facts for what you are buying. I say this based on having a good idea of how much these forks will need to dial in and keep consistent from ride to ride.

    Yes it is an easy fork to work on and maintain, but unless you want to take the time...you would likely rather be riding. For me, I am a suspension geek and have been working moto suspension and playing test rider since the mid 70's. Simple and easy in this situation may be a bit more than most folks care to play with.

    I am by no means disappointed in the ATC, and suspect I'll get a dialed setup for the hardtail Fandango 29r. It will take some work, involving testing and some tuning but it should be doable. The hardtail rear end can not out perform the ATC like the ECDM does.

    Time will tell what fork ultimately goes on the ECDM, but at the moment, the DHX 5.0 I installed on the rear dialed in real close to spot on with no big mods internally. Our greatest deviation from Foxes settings are running Pro Pedal threshold between clicks (non detent position). As I posted before, I am really leaning towards a modified Kashima FOX 40. Whatever route I take, I'll post the setup settings.

    PK
    Last edited by PMK; 08-21-2010 at 07:28 PM.

  38. #38
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    Marzocchi Jr. T. on Ellsworth. I limited the travel with internal spacers to 6". Using 15wt oil, played a bit with the damping, use the optional stiffest springs offered and bought seperately from Marzocchi, added air caps mostly to bleed off any accumulated pressure from time to time. No need to add air as the stiffer springs are just about right for my normal stoker. Adjusted the oil level down a bit to allow full stroke. Supple for the first part of the stroke, stiffens out well near the limit. Does eat the bumps well. The mods made it less bouncy and more confidence inspiring. Heavy steering feel. Has been a good fork for the job. No issues with seals and they are still going strong since new in 2002. As with any fork you can spend forever with the variables. You could make it a full time job just tuning forks and shocks. Certainly better than out of the box and no doubt I will continue to fiddle with it from time to time. I do like the fork. Lock out would be nice.

  39. #39
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    Jr T modification?

    Stevoo,

    Could you give more detail about your Jr T mod? I've got one at the original 170mm and would be very interested in lowering it to 150-160.

  40. #40
    PMK
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    In regards to the JrT's and Super T's, there are two different design platforms.

    For model years 2002 and prior they utilized 30mm upper tubes, 2003 and after went with 32mm upper tubes.

    By comparison, The WB 100's are 32mm uppers as are the USD type forks lowers.

    As I mentioned, I have a 170mm Marzzochi clipped to about 110mm. Typically, the mod is very easy. You'll need a piece of 1/8" wall thickness aluminum tubing to loosely slip over the cartridge body. If you want a 130mm travel fork make a 40mm spacer sleeve for each leg. If the fork has coil springs, they can be replaced with shorter springs, or if a spacer lives on the main spring, trim it to offset the spacer added to limit extension.

    For several years, and possibly still, Marzocchi was selling a second set of negative (top out) springs to shorten the forks from 130 to 100. This works, but can make the fork have a dead feel as opposed to being more lively at longer extensions.

    If you have down time later in the year, or want to send it here and back sooner I'll make the mod for you.

    Unfortunately I didn't take photos of the DO triple when I did it.

    PK

  41. #41
    PMK
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    Is anyone else running an ATC fork that reads these forums? Before I spend more time writing I wanted to see if it is even worthwhile.

    Our ECDM fork is what it is. Not bad but needs a revalve to get better. Sometimes notchy but mostly pretty smooth now.

    Our ATC on the Fandango 29r has been less consistent. After this weekends ride with some new simple mods, it has been smoother than the ECDM fork, and consistent for the entire rides.

    PK

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    I would be interested in more info on the Magic 100T. This is our second one on our ECDM and I find the newer one to be smoother, the break in was shorter and I run more air pressure than the one on our Fandango. We are a 360 # team. I would also like to hear about settings for the Fox RP3 rear shock but maybe that needs a whole different thread.
    I am running 55# of air in the Magic after setting the IMV valve about 6 clicks from wide open and the rebound screw closed about 3/4 of a turn. I am still adjusting as the fork is still breaking in somewhat. I am much happier with the new version. The 100T we had on our Fandango I ran only 30# of air, 3 clicks from wide open on IMV and wide open on compression and would still come back with sore hands and shoulders.
    On the RP3 I run 215# of air, rebound about 4 clicks, and we use pro pedal most of the time.
    I am still learning about suspension settings so please excuse any errors that are obvious.
    Ed and Pat Gifford
    Toms River, NJ

  43. #43
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    I am sooooooooo happy with the DUC32 I bought off ebay and sent to maverick to tune up and setup for our weight and riding style. Last weekend we rode the SM100 and it was flawless. Although I do not have much to compare it to I am so impressed with this lighter weight triple clamp fork. The only problems we had was with the timing chain and rear wheel.

  44. #44
    PMK
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    Ed I can't help with the WB stuff at this time. We don't have one to test or even go through basic settings.

    In regards to your RP3, when you run Pro Pedal, which PP setting. Our RP3 has the ability of selecting one of 3 settings.

    Reference page 11 of this manual

    http://www.foxracingshox.com/fox_tec...arShock_en.pdf

    Position 1 was way to soft and no amount of air pressure would take the marshmallow feel away.

    We tested in full PP but never rode while set there excepting dead smooth road sections, and even then, for us I believe the bike was faster not in #3.

    All our riding was done via PP2. This gave a decent compromise. Our settings were 225/230 PSI with a small can and team weight of about 370 plus gear.

    Besides revalving the RP3 for better rebound, now able to run 4 clicks out from full slow, I have made a conversion to the internal floating piston filler, so now it is more reliable and adjustable in pressure easily and without special tools. This can alter the internal progression of pressure, similar to, but not as extreme as on a DHX5.0 air.

    Consider also, that on many forks and rear dampers, that adjustments to the rebound can alter compression flows too as many rebounds are not checkplated and freebleed in two directions. As rebounds are opened or closed, this alters the pressure values inside the damper to unseat the compression shim stacks and can change the way the bike feels in some situations.

    PK
    Last edited by PMK; 09-07-2010 at 09:31 AM.

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    Hi Paul,
    We usually run PP3 and full suspension switching between the two as the conditions dictate. I also have been flirting with the idea of finding a PP2 setting that works for most conditions we ride. Sometimes my stoker becomes pre occupied with switching the settings and forgets about the other aspects of the ride.

  46. #46
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    Hi Paul,
    We usually run PP3 and full suspension switching between the two as the conditions dictate. I also have been flirting with the idea of finding a PP2 setting that works for most conditions we ride. Sometimes my stoker becomes pre occupied with switching the settings and forgets about the other aspects of the ride.
    Ed

  47. #47
    PMK
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    Ride a bit in PP2, make minor (1 click) changes to the rebound. Go firmer, ride a bit, go 2 clicks softer ride a bit. Work this until optimized.

    While testing try and ride sections that are all similar, or the same sections repeated. Don't let the stoker make a change until you have forced yourself to ride the entire section (unless dangerously wrong). Before making the change ask what she noticed, liked and didn't like.

    Once set, I doubt you'll need PP1 for anything except the moon, PP2 should be your home setting with PP3 for flats.

    With PP2 setup, the bike will bob some but if the air pressure is correct, it should be minimal, and give good results.

    Rebound set full closed or open is bad. Since the RP's don't use a rebound needle all settings can be used effectively, however, the shape of the ports does not have the same net change from one click to another. Best rebound settings are #3 thru #6.

    PK

  48. #48
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    Marz 66SL

    1. What fork make/model and what frame make/model?

    2006 Marz 66SL. This is the air version, no springs. Oil damping. On an '06 ECdM.

    1a. single or dual crown
    Single

    1b. lock out?
    No

    1c. axle type 20mm thru? 9mm QR?
    20mm through axle. Before Marz switched to a QR 20mm axle.

    2. Team weight?
    Probably 380ish with gear and water

    3. Type of riding.
    Everything this side of drops and jumps. Fireroad, singletrack, rutted singletrack, dry creek crossings, sections of boulder downhill.

    4. Any feedback regarding performance, maintenance etc. (positive or negative).

    Aside from the poor Marz owner's manual (one manual per model year, despite the vast number of different forks produced for that year, makes it very difficult to figure out which acronyms apply). Worse that there were a half-dozen 66 models produced, so it took quite a bit of time to find the correct service manual.

    Use has been great, so far as my knowledge goes. I run the positive air at ~145lb, negative at ~40. Have come close to using all the travel a handful of times, but most it sags about 20% and I use another 40% when riding, according to the stanchion zip tie. Has provided a stable platform when we hit rough stuff. Probably a bit tall for our needs.

    Maintenance isn't difficult. Again with the task of finding the correct service manual. I did fill the oil to the specified amounts (200ml in left, 50 in right), but came away with a very harsh top-out. Another 50ml in the right leg cured that. Otherwise a seal kit and a couple hours did the job. Not as easy as the RP3, but, hey...

    On RP3 notes, we use ~170lb in the can with ProPedal set on. I tried to get my stoker to play with some of the settings to figure out what she likes and likes better, but that never got very far. Via the witness ring, we use up about 85% of travel at that pressure.
    Attached Thumbnails Attached Thumbnails Suspension Fork Experience - What's Working? What's Not?-img_2817.jpg  


  49. #49
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    Borrowed from the "New ECdM Build Advice" thread, TandemNut said:

    Quote Originally Posted by TandemNut
    Second the Marzocchi option for single crown, but team weight has a bearing on that as well; typically teams over 300lbs are better suited to double-crown forks.
    So, given that our team weight is ~360lb with gear and we ride hard enough to go through three WI rear hubs and crack the ECdM frame, is there a more definite weight limit for an '06 Marz 66SL? I did not detect any damage/fatigue when the fork was out during the rebuild and I don't want to be surprised by it on the trail.

  50. #50
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    Quote Originally Posted by Okayfine
    Borrowed from the "New ECdM Build Advice" thread, TandemNut said:



    So, given that our team weight is ~360lb with gear and we ride hard enough to go through three WI rear hubs and crack the ECdM frame, is there a more definite weight limit for an '06 Marz 66SL? I did not detect any damage/fatigue when the fork was out during the rebuild and I don't want to be surprised by it on the trail.

    Most modern large tube forks are pretty well built structurally. Most times it's not going to be a catastrophic structural failure but rather cyclic stress type failure. Pretty much a situation of how many times can you bend the beer can before it breaks, not so much a John Belushi smashing the beer can on his head Ala "Animal House".

    Best to do visual inspections at higher stress locations like the crown, bridge, axle mounts, and lower legs about half way between the seal and axle.

    Should you plan to find something, NO. Could you find something, Yes.

    In regards to single crown vs double, the obvious advantage is much less flex loads into the double crown. Aside from that, the lowers and bridge see the same, and possibly more stress in some cases than a single crown. One other big consideration to loads induced into the forks is extended length. It can be nice to have lots of travel, but with it comes added torsional and front to rear flex.

    We don't ride a single crown fork on our tandems. I'm pretty confident we could on our XC Fandango, but the ATC is now working very well so it will stay. As for the ECDM, where and what we ride I would not have faith in a single crown lasting very long. If it ever gets here, a Fox40 Kashima is going to replace the ATC not on account of flex or lacking structural strength, we just need better damping control.

    PK

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    Hi Paul,
    We have been fooling around with the rear shock adjustments under various conditions for the last week trying to find the acceptable set up for PP2. Amazingly we seemed to have settled on just about the same as yours even though I tried a lot of different things with air pressure and rebound. We currently run 230 # air pressure and 5 clicks from open on PP2 and the bike handles well under all but the most exteme conditions and my stoker is comfortable and happy. Yesterday we did a 30 mile ride on a canal path ( think rail trail) as a test for PP3. It felt very reminiscent of our Fandango hardtail but more comfy over any ruts or bumps. Smooth and fast. The only time we had any bobbing problems was in standing and that is more of a technique issue rather than a suspension issue.
    Ed

  52. #52
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    Ed,

    Glad to hear you have tested a bit to find better settings. Your setup runs similar to ours, but most important is it is pretty much up the middle on the rebound clicker. The nice thing about being dialed on PP2 is the bike has a wider terrain envelope and can inspire more confidence as you carry momentum and more speed through sections.

    PP1, is very soft on compression damping. It will be cushy for anyone that rides it, provided there is enough air pressure to hold the back end up on rolling bumps. With PP1 selected the terrain envelope is good for roots and rocks when the bike / team does not carry much momentum across those features. In my opinion the setting is marshmallow soft and the rear end wallows constantly for us. It is especially unnerving in fast corners as the rear end is bobbing and constantly changing the headtube angle and steering feel + inputs. I work harder in PP1 and we go slower, also the stoker doesn't like it blowing through the stroke and wacking pedals. If we still ran an RP series damper, PP1 would be our mud setting, slower speeds, softer damping to keep the rear wheel compliant over super slippery stuff, or hooked up in low grip conditions.

    PP2 when setup well, will provide enough spring rate (psi) and firm the damping. Some times firmer damping can cause deflection issues on roots and rocks. The PP2 setting for us would unload the damper (blowoff) on extreme hits, but gave a good balance for rolling terrain and the high speed compression stuff like rocks and roots. Like almost all suspended vehicles, often times firmer damping, provides the control needed to ride rough sections at greater speeds and with more control.

    The secondary benefit of PP2, is this setting should be pretty good for all but the smoothest terrain. Plus PP2 will save your frame from being pounded to death via lockout on rough terrain.

    As for PP3, we only will run a full lockout on pavement or dirt roads.

    With us now running a DHX5.0 air, the version we have is clicker adjustable PP amounts. For us this works well, and let's the compression settings be better optimized, rebound also.

    I spoke with Sherwood recently about something unrelated. The DHX damper was brought up. As he indicated, and I agree fully long before the conversation, sometimes having more features can make finding optimum settings more difficult. The DHX has been a good mod for us. Unfortunately it is not a plug and play swap. The air can volume is not optimized for the linkage rates of the ECDM and does not work well for us in regards to spring rate progression. Once this was settled, the air spring pressure was optimized, followed easily by rebound. The PP settings were a bit of a learning curve for Jeanne. The best method to optimize the back is to force the stoker to make changes and learn about how the bike reacts differently with each change. Even with an RP damper, move the rebound, to full open then full closed several minutes later. Then go back to center. Ride that for a short bit and open it a couple of clicks, then go back past center and run it with more rebound.

    Eventually, the stoker should be able to find a setting that does not bounce her off the saddle, but is fast enough rebound that the captain retains lighter steering inputs and the bike turns consistently and predictable.

    Dialing in clickers and oil levels (in forks), plus ensuring you have the proper springs can be a huge difference in how a bike feels and rides.

    Glad you got it sorted out. Should be a faster safer bike to ride, and that is a good thing for you, maybe not others.

    PK

  53. #53
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    As noted in the ECDM topic, our current fork is a Fox 40 Kashima.

    We are running the firmest spring (red) with the travel set to 5 1/2".

    The good about the fork is how tunable and it's ability to work very well on all terrain.

    The downside is the obvious stupid expensive cost.

    The other downside was Fox as a company and their lack of getting the gold Kashima tubes close to the same color when they built it. We have one darker gold tube and one lighter gold tube. When asked about it, they said they are all this way, which is obviously not true.

    The only way they would even consider, but not promising a matched tube set, was to send it in for warranty and wait.

    If you consider this fork, be aware that you will need a different brake adapter for the caliper. The 203mm disc uses a smaller adapter, not uncommon but just worth noting when you order your fork. We went to Avid BB7's and I believe I had to install a 160 front adapter. No big deal.

    Additionally, I plan to buy another axle if they are reasonable. When transporting in the van, I use a Hurricane fork up on a BikeTight platform. The Hurricane adapter is a loose fit to the axle and the bike rocks back and forth. Regardless, I either need to line the ForkUp with a plastic tube to prevent axle wear or have one axle for transporting.

    If you have an old school Manitou 5mm super long allen wrench, dig it out. These work great for removing and installing the front wheel.

    Performance wise, the added shortening spacers increase the preload on the spring to a proper amount for us at 355 plus gear. The spring rate is decent.

    Damping wise, the fork has adjustments for low speed compression, high speed compression, and rebound. With no shimstack changes the fork dialed in via the clickers.

    One other motorcycle carryover used in the Fox 40 is bottoming control. I have not opened this fork, but if memory is correct it uses a bottoming cone type setup to gradually slow the fork as it reaches full stroke. We have ridden it and seen the "O"ring witness band pushed to 100%, but I can not recall feeling the bottoming in the bars.

    As I noted in the other topic, this fork is very capable and lends itself to making a rider very confident, it lets you ride faster while safer, but when you miss a good line, you are going a good clip headed off course.

    We like it and don't have any plans to make further changes.

    Like so many things, not tandem rated but could be something to consider.

    PK

  54. #54
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    Quote Originally Posted by PMK
    Additionally, I plan to buy another axle if they are reasonable. When transporting in the van, I use a Hurricane fork up on a BikeTight platform. The Hurricane adapter is a loose fit to the axle and the bike rocks back and forth. Regardless, I either need to line the ForkUp with a plastic tube to prevent axle wear or have one axle for transporting.
    This is interesting. I made a 20mm "Fork Up" type mount, but used 3/4" black pipe (from Home Depot, for gas work) and it is slightly too big in ID for the axle...so it wobbles during transport! I kept thinking about buying a legit item (but thinking $50 was highway robbery), thinking it'd be a perfect fit. Good to know.

    I've used a piece of Teflon sheet (had some extra from an old project) to line the inside. Still wobbled a bit, but the axle was protected.

  55. #55
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    Fox 40

    Fox 40 with their heaviest spring, Bicycle Fabrications Tandem 8" travel F&R.
    Riders weigh 380lbs +70lb bike.
    Downhill riding, resort and trail, jumps, drops, high speed.
    Fox makes some stout products, the heavy spring nicely matches the 700lb DHX 5.0 spring in the rear, all the travel has been used but no hard bottom out..... yet.
    Attached Thumbnails Attached Thumbnails Suspension Fork Experience - What's Working? What's Not?-t-1-xxsm.jpg  

    Suspension Fork Experience - What's Working? What's Not?-t-3-xxsm.jpg  


  56. #56
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    I was curious and went looking for Bicycle Fabrications and found their website.

    The 70lb bike spec had me wondering why. This bike is in some photos on their website. Definitely a rugged race bike, all steel US made machine.

    Here's a photo from the websites photo section

    http://www.bicyclefabrications.com/B...ecial_P.html#3

    Very nice, though a bit overkill for XC riding.

    I may steal your idea of multiple steering lock cushions, very good idea.

    PK

  57. #57
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    Quote Originally Posted by Trails4Two
    Stevoo,

    Could you give more detail about your Jr T mod? I've got one at the original 170mm and would be very interested in lowering it to 150-160.
    Trails4Two, did you ever get the info you needed for your fork mod?

    I've got a Jr T shortened to 130mm. Easy! I spoke with the folks at Marz and they seemed confused when I said I wanted to buy a kit for shortening the fork.
    "Just cut a spacer to the length you want." He recommended plastic (PVC or ABS?), but the pipe I bought was too large, so I ended up cutting a 40mm piece of of an old handlebar.

    I seem to recall placing the spacer above the top-out spring. It's been a few years. Let me know if you have questions.

  58. #58
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    Jr T mod

    Did the spacer addition change the spring rate (make it stiffer)? It's not that critical since I did a pretty big handlebar/stem swap to get some weight off my hands, and in so doing happened to get the fork dialed in really well. We are really happy with it even in full travel right now. For an inexpensive fork it really eats up everything we throw at it.

  59. #59
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    Quote Originally Posted by Trails4Two
    Did the spacer addition change the spring rate (make it stiffer)? It's not that critical since I did a pretty big handlebar/stem swap to get some weight off my hands, and in so doing happened to get the fork dialed in really well. We are really happy with it even in full travel right now. For an inexpensive fork it really eats up everything we throw at it.
    Good point. As I said it had ben a while. There is a preload spacer above the spring which is about 60mm stock. It can be shortened or replaced to suit. I replaced mine, ultimately increasing spring preload by about 20mm. It can be challenging to replace the topcap if there is too much preload.

    So you've got a more upright riding position on your bike? There is a guy in Phoenix that had his tandem set up that way....You like it? Pictures?

  60. #60
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    1. What fork make/model and what frame make/model?
    Marz Jr T @130mm (orig 170) Stiffest springs w/air caps
    Ventana ECDM 2006

    1a. single or dual crown
    Dual Crown

    1b. lock out?
    No

    1c. axle type 20mm thru? 9mm QR?
    20mm. I would not go back to 9mm on a mtb tandem.

    2. Team weight?
    350lbs, was 375-380 (capt lost weight)

    3. Type of riding.
    Singletrack, often rocky

    4. Any feedback regarding performance, maintenance etc. (positive or negative).
    Not nearly as stiff in terms of steering and deflection on old ZZYYX or ATC, but very smooth in terms of bump compliance. I run around 20psi in each leg, but initial travel is still a little too soft. I've gone to 10wt oil (from 7) and I will try heavier still next time I'm tinkering. Also less steering lock compared to ATC.

    No maintenance issues. One seal may be leaking a little after 4 years. Not bad.

  61. #61
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    FWIW, when shortening forks, consider also the volume in the air chamber is decreased.

    If you run the same amount of fluid, either by measuring volume in cc or ml, or doing a dimensional check on a fully bled fork, you will lose spring rate of the air spring on account of it not building 40mm of travel pressure.

    So, if you shorten a wet fork, to regain bottoming resistance, which most shortened forks will need, plan on adding some fluid.

    PK

  62. #62
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    Quote Originally Posted by reamer41
    1. What fork make/model and what frame make/model?
    Marz Jr T @130mm (orig 170) Stiffest springs w/air caps
    Ventana ECDM 2006
    .
    What year is the JrT? More importantly, what are the tube diameters, 30mm or 32mm?

    The 2mm is a large percentage change in cross section and stiffness provided they did not try to retain flew for a better ride quality.

    PK

  63. #63
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    Quote Originally Posted by PMK
    FWIW, when shortening forks, consider also the volume in the air chamber is decreased.

    If you run the same amount of fluid, either by measuring volume in cc or ml, or doing a dimensional check on a fully bled fork, you will lose spring rate of the air spring on account of it not building 40mm of travel pressure.

    So, if you shorten a wet fork, to regain bottoming resistance, which most shortened forks will need, plan on adding some fluid.

    PK
    Hmmm. I had increased fluid volume somewhat. I don't remember exactly how much, and I'm not at home now.
    Anyway, I had recently been condidering reducing fluid and increasing air pressure as I havent been noticing bottoming (but have been using the full stroke) and have been blowing through the initial stroke very easily. My thinking, however flawed, was that by gaining a larger air volume and increasing pressure I would get a stiffer spring rate that is more linear.

    From your initial comment, I'm thinking I was off base here... Thoughts?

  64. #64
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    Quote Originally Posted by PMK
    What year is the JrT? More importantly, what are the tube diameters, 30mm or 32mm?

    The 2mm is a large percentage change in cross section and stiffness provided they did not try to retain flew for a better ride quality.

    PK
    I don't know. I bought the fork from Alex in 2006, but I don't know the model year.
    I've never measured and I'm a couple thousand miles from home. I'll measure when I get home. From looking at the Marz website, I'm thinking it's a 2006 w/32mm tubes.

  65. #65
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    Quote Originally Posted by reamer41
    Hmmm. I had increased fluid volume somewhat. I don't remember exactly how much, and I'm not at home now.
    Anyway, I had recently been condidering reducing fluid and increasing air pressure as I havent been noticing bottoming (but have been using the full stroke) and have been blowing through the initial stroke very easily. My thinking, however flawed, was that by gaining a larger air volume and increasing pressure I would get a stiffer spring rate that is more linear.

    From your initial comment, I'm thinking I was off base here... Thoughts?
    Not to avoid a direct answer, but there is not enough information to give good feedback.

    Typically, springs support and damping controls.

    The key here is are you blowing through the stroke, or need more preload and mid stroke support.

    Additionally, is the fork harsh in any way on small square edge bumps. If not, I would add compression damping first, if it's underdamped, no amount of spring will keep it riding proper.

    Increasing viscosity will also add to the high speed rebound which will keep the front wheel more planted.

    PK

  66. #66
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    Quote Originally Posted by PMK
    Not to avoid a direct answer, but there is not enough information to give good feedback.

    Typically, springs support and damping controls.

    The key here is are you blowing through the stroke, or need more preload and mid stroke support.

    Additionally, is the fork harsh in any way on small square edge bumps. If not, I would add compression damping first, if it's underdamped, no amount of spring will keep it riding proper.

    Increasing viscosity will also add to the high speed rebound which will keep the front wheel more planted.

    PK
    The fork is not harsh at all. I have felt it is under damped, and I will try a more viscous oil. I've already gone from 7.5 to 10. Any recommendation on brand and/or weight of oil?

  67. #67
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    Quote Originally Posted by reamer41
    The fork is not harsh at all. I have felt it is under damped, and I will try a more viscous oil. I've already gone from 7.5 to 10. Any recommendation on brand and/or weight of oil?
    What brand and spec is the oil you had and went to?

    The easiest way to know if your change was good our bad is to compare the fluid on PVD's wikki chart.

    http://www.pvdwiki.com/index.php?title=Suspension_Fluid

    Use the viscosity of cSt (centistokes) @40 degrees C.

    Also, find fluids for your fork with lower VI ratings, typically they have better "slippery" performance which is good for an open fork.

    If you have any cartridge type forks, or are rebuilding a rear damper, look for higher VI rated fluids since the rear damper works much harder than the forks.

    For a tandem with a simple rebound tune only fork I wouldn't be hesitant to look at stuff in the 20 wt range, 60 ish on cSt.

    You asked for a recomendation, even though this is not a 20wt, it has decent numbers.
    Motorex racing fork oil 15wt, 69.80 cSt @ 40C and a 160 VI. If you have a local CycleGear, motorcycle accessory shop, they may stock it, I have seen them carry Motorex fluids before.

    Don't be afraid to accurately work the fluid level to gain a firmer mid travel spring rate AND to minimize fork dive and bottoming.

    PK
    Last edited by PMK; 12-31-2010 at 05:14 AM.

  68. #68
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    Quote Originally Posted by PMK
    What brand and spec is the oil you had and went to?

    The easiest way to know if your change was good our bad is to compare the fluid on PVD's wikki chart.

    http://www.pvdwiki.com/index.php?title=Suspension_Fluid

    Use the viscosity of cSt (centistokes) @40 degrees C.

    Also, find fluids for your fork with lower VI ratings, typically they have better "slippery" performance which is good for an open fork.

    If you have any cartridge type forks, or are rebuilding a rear damper, look for higher VI rated fluids since the rear damper works much harder than the forks.

    For a tandem with a simple rebound tune only fork I wouldn't be hesitant to look at stuff in the 20 wt range, 60 ish on cSt.

    You asked for a recomendation, even though this is not a 20wt, it has decent numbers.
    Motorex racing fork oil 15wt, 69.80 cSt @ 40C and a 160 VI. If you have a local CycleGear, motorcycle accessory shop, they may stock it, I have seen them carry Motorex fluids before.
    PK
    Ah, I had been looking at PVD's site even before you posted it. Lots of information there. Who would have thought that the "weight" of oil changes from one brand to another. Is motor oil similarly varied, I wonder?

    OK. So I'm back home. Answers to questions asked. I do have 32mm fork tubes. The last batch of fork oil I used is Bel-Ray High Performance fork oil 10W. From the PVD table that shows a cSt of 33.5, which looks to be in the right direction from the stock of 26.1. There is a cycle gear shop near by. I'll see if they are carrying the Motrex 15wt and give it a try.


    Quote Originally Posted by PMK
    Don't be afraid to accurately work the fluid level to gain a firmer mid travel spring rate AND to minimize fork dive and bottoming.
    PK
    Well, I won't be afraid to do that, I'm just not sure that I know what I'm doing.

    Thanks for your help, PMD. I'll update with results.

  69. #69
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    Cycle Gear didn't have the Motrex, but had Maxima 20wt (cSt@40 65.60), which has similar numbers on the PVD chart. So I gave that a try. What a difference!

    Fork felt much more stable when cornering on relatively smooth trail, but harsh over bumps. Even small rocks were a little jarring. Also, even when set up with too much sag we never used the last inch of travel -- even off a 18" drop. I felt it quite difficult to control the bike on a rocky downhill.

    When draining the old fluid I was reminded that I had previously lowered the fluid volume to regain the last inch of shock stroke. Maybe I had taken it too low, but the recommended 265cc seems to be too much. I am using air-caps and have been using about 20psi to get about 1.25" sag.

    I will try reducing fluid volume a little bit at a time, but the harshness felt on rocky trails leads me to believe that something between the Bel-Ray 10wt and the Maxima 20wt might be the ticket.
    Last edited by reamer41; 01-03-2011 at 01:08 PM.

  70. #70
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    Take a photo of the fork caps.

    I would not, unless I had no other means use a volume amount for how much oil. The best way is to overfill and suck out the excess.

    You ensure the cartridge is bled 1005 by cycling the damper rod, then fully compress the fork. Use a syringe with a hose, or an old spray bottle. Mark the depth and remove the excess fluid.

    You should realy think any change through on an air sprung fork.

    Consider if you had to much fluid, it will not use full travel. If you lower the pressure the fork gets harsh.

    Run the most preload or air pressure to support the front that gives good small bump compliance, then retain that pressure while decreasing the oil level.

    The reality check is that you need to balance small bump compliance, mid stroke support (for good handling) and bottoming.

    BTW, Maxima is good stuff too. Testing with the same brand and dropping a viscosity may dial it in as you mentioned. The problem may be the cartridge is not capable of the load.

    I have a Marzocchi Drop Off Triple I never installed. Shortened the travel, and so on. It is a very basic fork, but one I know will handle the damping loads with no issue. The simplicity and non cartridge design are what will let it work.

    The is a fine balance on a cartridge setup where you must retain enough cartridge pressure for the fork to function, but still unload enough hydraulic pressure to prevent harshness.

    PK

  71. #71
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    Also,if I get a chance, I'll post some video we got this weekend. Pretty graphis of just how much punishment these bikes take when riding them.

    It may give you some ideas on tuning the fork.

    PK

  72. #72
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    Quote Originally Posted by PMK
    Take a photo of the fork caps.

    I would not, unless I had no other means use a volume amount for how much oil. The best way is to overfill and suck out the excess.

    You ensure the cartridge is bled 1005 by cycling the damper rod, then fully compress the fork. Use a syringe with a hose, or an old spray bottle. Mark the depth and remove the excess fluid.

    You should realy think any change through on an air sprung fork.

    Consider if you had to much fluid, it will not use full travel. If you lower the pressure the fork gets harsh.

    Run the most preload or air pressure to support the front that gives good small bump compliance, then retain that pressure while decreasing the oil level.

    The reality check is that you need to balance small bump compliance, mid stroke support (for good handling) and bottoming.

    BTW, Maxima is good stuff too. Testing with the same brand and dropping a viscosity may dial it in as you mentioned. The problem may be the cartridge is not capable of the load.

    I have a Marzocchi Drop Off Triple I never installed. Shortened the travel, and so on. It is a very basic fork, but one I know will handle the damping loads with no issue. The simplicity and non cartridge design are what will let it work.
    PK
    Thanks for your response. It leave me with a couple questions: The Marzocchi manual gives fluid in CCs. You are saying better to measure the level, right? I am assuming (always dangerous) that you would measure from the top of the tube with fork compressed and springs removed. That right? I guess it doesn't matter as long as you do it the same way each time. How do you establish the starting fluid level?
    265CCs doesn't leave much air-volume when the forks are fully compressed.

    You wrote:Consider if you had to much fluid, it will not use full travel. If you lower the pressure the fork gets harsh.

    I think I may not have been clear in my post above. The fork was harsh all the time, with 20psi and still harsh with only 10psi. I reduced the pressure to see if we would use more travel, not due to harshness. But still we did not use the last inch.

    With these air caps it is hard to preload the coil springs. Considering I'm using air pressure should I, and how much should I, preload the springs? It is a little tricky to thread these non adjustable caps on while holding down a bunch of spring pressure.

    Here are the caps, and for good measure the springs...
    Attached Thumbnails Attached Thumbnails Suspension Fork Experience - What's Working? What's Not?-cap-side.jpg  

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

    Attached Images Attached Images  

  73. #73
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    That's what I wondered, similar to my Drop Off Triple, except I have single springs.

    So now tell me because I don't want to confuse your fork with others, where is the rebound clicker, internal or external, photo of that and have you adjusted it to make the fork react better?

    PK

  74. #74
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    You are correct, fully bleed any cartridge device by cycling the damper shaft. Fully bottom out the fork. No springs, damper rods fully plunged if applicable.

    Set your depth tool for however many mm of fluid. Suck it to that level.

    By using a simple spray bottle, remove the bottle, remove the little filter screen if it has one, use masking tape to indicate the depth. Slide the tube into the fork and while maintaining the set depth, pump and spray the excess fluid into the bottle. If the fork has been cleaned and this is it's first reset, you might even spray it into the container.

    PK

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    Quote Originally Posted by PMK
    That's what I wondered, similar to my Drop Off Triple, except I have single springs.

    So now tell me because I don't want to confuse your fork with others, where is the rebound clicker, internal or external, photo of that and have you adjusted it to make the fork react better?

    PK
    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.
    Attached Files Attached Files

  76. #76
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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.



    This is what your fork has to keep up with.

    PK
    Last edited by PMK; 01-04-2011 at 12:30 AM.

  77. #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

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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  


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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.



    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 08:53 PM.

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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...

  81. #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

  82. #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?

  83. #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

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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.

  85. #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.

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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.


  87. #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.


    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 12:14 PM.

  88. #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 01:35 PM.

  89. #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

  90. #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

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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

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

  93. #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

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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!

  95. #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

  96. #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

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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

  98. #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

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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!

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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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