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  1. #1
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    Freedrive...single-pivot suspension?

    Hi, after taking close looks at the Freedrive suspension said by some to be similar to the GT's single-pivot I-Drive suspsension system, can anyone tell whether the the Freedrive is considered just a single-pivot suspension system? Which pivot exactly functions as the main pivot of the whole system then? Doesn' it look really like a kind of virtual-pivot system instead? Trying to see how the whole combination of linkgs work/moves is rather hard for me in this case....too many links!

    Regards,


  2. #2
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    In response to your PM inviting me to comment, I am happy to TRY to help. I have not ridden this design, so I would guess that it rides pretty well, but riding experience is the true test for any design to see if it works well for each rider's unique style and environment. As background, I am an avid trail rider of about 30 years, went to full suspension 15 years ago, fascinated by suspension dynamics, with a curiosity to ask questions where I don't understand. I have made some wrong statements in the past and will make more errors in the future. I've learned a lot about the physics and forces, but I am not formally educated in suspension, only a critical rider and tuner.

    I feel there are three major reactive conditions for full suspension, acceleration anti-squat, rider weight shift response, and handling balance or "feel".

    Isolating anti-squat in the Freedrive appears pretty simple initially as something like a high monopivot or URT, but is complicated and balanced with the rider weight-shift by the multi-links with the shock. I would generally categorize the design as a multi-linked URT-like (unified rear triangle) design, with some relation to GT’s Independent-Drive and Maverick suspension designs.

    I can only guess, this design is so complicated that a computer dynamic modeling would be needed to identify the force reactions, but it appear the acceleration force is focused though the upper swingarm pivot with the center frame, and would counter-act acceleration squat, and produce anti-squat much like a "sweet-spot" monpivot URT like the mid '90's Ibis Swabo. Similar to monopivot URT's, without corresponding downward force from rider pedaling input weight-shift, the suspension might "inchworm", extend, while pedaling more like an the later '90's Klien Mantra URT, but the rider's oscillating down force input while pedaling should keep the suspension stable. Rear only braking, like "sweet-spot" URT's might be stable but a little stiffening and loose traction easily over stutter bumps if the rider doesn't move their body weight rearward before braking.

    It appears to me that the linkage to the shock is just that, a complicated way to produce a rather linear leverage to a rising rate air sprung shock, producing a rising rate overall suspension, or "wheel rate", bringing nice small bump compliance, an big hit and bottomless feel plushness.

    Again I have not ridden this design, it is complicated by the multi-linked shock and floating BB, but it appears to be mainly URT-like in effect. I need to ride one to validate my semi-educated guesses. I hope this estimation isn't too far off.

    Ride it and see how it feels. Riding is the true test.

    Edit: "URT-like"
    Last edited by derby; 03-26-2010 at 07:46 PM.

  3. #3
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    Thank you, derby...

    Quote Originally Posted by derby
    In response to your PM inviting me to comment, I am happy to TRY to help. I have not ridden this design, so I would guess that it rides pretty well, but riding experience is the true test for any design to see if it works well for each rider's unique style and environment. As background, I am an avid trail rider of about 30 years, went to full suspension 15 years ago, fascinated by suspension dynamics, with a curiosity to ask questions where I don't understand. I have made some wrong statements in the past and will make more errors in the future. I've learned a lot about the physics and forces, but I am not formally educated in suspension, only a critical rider and tuner.

    I feel there are three major reactive conditions for full suspension, acceleration anti-squat, rider weight shift response, and handling balance or "feel".

    Isolating anti-squat in the Freedrive appears pretty simple initially as something like a high monopivot or URT, but is complicated and balanced with the rider weight-shift by the multi-links with the shock. I would generally categorize the design as a multi-linked URT (unified rear triangle) design, with some relation to GTs Independent-Drive and Maverick suspension designs.

    I can only guess, this design is so complicated that a computer dynamic modeling would be needed to identify the force reactions, but it appear the acceleration force is focused though the upper swingarm pivot with the center frame, and would counter-act acceleration squat, and produce anti-squat much like a "sweet-spot" monpivot URT like the mid '90's Ibis Swabo. Similar to monopivot URT's, without corresponding downward force from rider pedaling input weight-shift, the suspension might "inchworm", extend, while pedaling more like an the later '90's Klien Mantra URT, but the rider's oscillating down force input while pedaling should keep the suspension stable. Rear only braking, like "sweet-spot" URT's might be stable but a little stiffening and loose traction easily over stutter bumps if the rider doesn't move their body weight rearward before braking.

    It appears to me that the linkage to the shock is just that, a complicated way to produce a rather linear leverage to a rising rate air sprung shock, producing a rising rate overall suspension, or "wheel rate", bringing nice small bump compliance, an big hit and bottomless feel plushness.

    Again I have not ridden this design, it is complicated by the multi-linked shock and floating BB, but it appears to be mainly URT like in effect. I need to ride one to validate my semi-educated guesses. I hope this estimation isn't too far off.

    Ride it and see how it feels. Riding is the true test.
    and now I need to start some more study based on your explanation above. It is complicated to me. I hope I can understand this soon.

    Appreciate you time for this and hope you stay sharing your opinions about suspension whenever possible.

    Regards,

  4. #4
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    Hahaha, you called Derby in as if he's an expert. Search through mtbr. He's been a joke for years here.

  5. #5
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    Quote Originally Posted by glitz
    Hahaha, you called Derby in as if he's an expert. Search through mtbr. He's been a joke for years here.
    Was that really necessary? He's trying to be helpful and he seems to have a pretty good knowledge base about bike suspensions. I think everyone already knows to take what they read on the internet with a grain of salt . . . .

  6. #6
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    Quote Originally Posted by Canaan
    Was that really necessary? He's trying to be helpful and he seems to have a pretty good knowledge base about bike suspensions. I think everyone already knows to take what they read on the internet with a grain of salt . . . .
    BWAHAHAHAHAHAHAA

    Did you even read his post?

    Why did you feel the need to post? You could have taken my post with a grain of salt, too...

    The knowledgeable people don't even post on mtbr anymore because of the degree of dilution of information and encouragement of agenda/adevertising driven nonsense.
    Last edited by glitz; 03-25-2010 at 10:04 AM.

  7. #7
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    Quote Originally Posted by derby
    I would generally categorize the design as a multi-linked URT (unified rear triangle) design, with some relation to GTs Independent-Drive and Maverick suspension designs.
    It is nothing like a URT and doesn't possess a URT's defining characteristic. GT's i-drive and Mavericks' suspension aren't URTs either.

  8. #8
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    Quote Originally Posted by glitz
    BWAHAHAHAHAHAHAA

    Did you even read his post?

    Why did you feel the need to post?
    1) Yes; and
    2) Because it seemed like you were going out of your way to be a prick.

  9. #9
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    Can it be?

    Quote Originally Posted by bad mechanic
    It is nothing like a URT and doesn't possess a URT's defining characteristic. GT's i-drive and Mavericks' suspension aren't URTs either.
    Based on a small link placed between the bb and the chainstay, can this Freedrive be chatacterized as a kind of virtual pivot suspension like that of VPP?

    Regards,

  10. #10
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    Attached are excerpts from a NSMB review of a Mongoose Pinn'r and a link to a Mongoose video about the Freedrive design. Hope you find these useful.

    "FreeDrive shares patents with both GT and Maverick bikes and is basically a very high-point single pivot design. The single pivot is married to the rear triangle through a small pivot and to the frame through a massive link that is built around the bottom bracket. It also directly connects to and activates the shock, allowing the bottom bracket to float or move with the suspension."

    http://www.mongoose.com/usa/eng/mtn/newsDetail?id=617

  11. #11
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    From the video

    Quote Originally Posted by Canaan
    Attached are excerpts from a NSMB review of a Mongoose Pinn'r and a link to a Mongoose video about the Freedrive design. Hope you find these useful.

    "FreeDrive shares patents with both GT and Maverick bikes and is basically a very high-point single pivot design. The single pivot is married to the rear triangle through a small pivot and to the frame through a massive link that is built around the bottom bracket. It also directly connects to and activates the shock, allowing the bottom bracket to float or move with the suspension."

    http://www.mongoose.com/usa/eng/mtn/newsDetail?id=617
    Thanks a lot for that useful video link.

    From the video, I now know where the main pivot is located. However, I still wonder what practical function that black small link (bb and chainstay) is....

    There should be some significant function for this small link to be put there.

    Regards,

  12. #12
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    I had a real hard time visualizing how that system works, too. I can tell you it does work though. I've got a 2008 Canaan Comp with a Fox Float R and I love the way it climbs and descends. Seems to have less pedal bob than the Stumpy FSR I rode on vacation, even without the ProPedal feature the Stumpy had.

  13. #13
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    Quote Originally Posted by JoeC
    Based on a small link placed between the bb and the chainstay, can this Freedrive be chatacterized as a kind of virtual pivot suspension like that of VPP?

    Regards,
    Hey JoeC, you are welcome, thanks for the invitation. I enjoy learning from mistakes and building on over a decade of knowledge from questioning other's theories and critique of my perspectives and interpretation. I question manufacturing marketing claims and sales hype, sometimes there is truth, but not much. The ride is the true test, and the best you know is only the best you've ridden.

    Obviously the Freedrive is not a standard monopivot, the BB floats not with the center frame but most directly with the rear swingarm like a URT to nearly eliminate any chain tension reactively, even more directly so in horizontal and vertical link angles than the similar floating BB designs of the i-drive and Maverick, so I call it a multi-linked-semi-URT-like design.

    There could be an effective virtual URT pivot. If you extend lines across a 4 pivots, 2 lines intersect, and the intersection from links off of a floating or isolated axle is typically called the IC (Instant Center). The IC is not a pivot when there is chain tension bringing another line of force, but does describe the angle of a virtual swingarm with the axle. In the case of the Freedrive, such as swingarm line would cross the BB constantly during travel. But the Freedrive is reported to have very little pedaling bob action unlike the massive pedaling bob a low angled swingarm would produce, so I think the pedaling dynamics are very similar to URT-like with the upper swingarm pivot.

    Watching the Mongoose video, Eric Carter describes a very active braking suspension. So it must be that the braking dynamics activate around the virtual pivot of the near BB location of the IC and produce a very active while braking suspension (to correct my first post above where I thought it might be stiffening like a high-monopivot URT). No one else has ever discussed the IC/Virtual pivot concept in any depth anywhere on the web that I seen when it related to floating BB designs.

    Hopefully, someone with greater knowledge can comment. I know there are many others on MTBR like me who what to learn more about suspension design theory.

    Edit: "...URT-like"
    Last edited by derby; 03-26-2010 at 07:48 PM.

  14. #14
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    Could we please stop using the term "URT"? Is there a pivot between the rear axle and BB? Yes, therefore it's not a URT. There's no "semi-URT"; it's either a unified rear triangle, or it's not.

    EDIT: Goofed up wrote "No" when I meant "Yes".
    Last edited by bad mechanic; 03-26-2010 at 09:21 AM.

  15. #15
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    Quote Originally Posted by bad mechanic
    Could we please stop using the term "URT"? Is there a pivot between the rear axle and BB? No, therefore it's not a URT. There's no "semi-URT"; it's either a unified rear triangle, or it's not.
    There are two pivot points between the rear axel and BB.

  16. #16
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    Quote Originally Posted by mullen119
    There are two pivot points between the rear axel and BB.
    I goofed up my previous post and have fixed it. What I meant to write was if there are any pivots between the bb and rear axle, then it's not a URT.

  17. #17
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    Quote Originally Posted by JoeC
    Hi, after taking close looks at the Freedrive suspension said by some to be similar to the GT's single-pivot I-Drive suspsension system, can anyone tell whether the the Freedrive is considered just a single-pivot suspension system? Which pivot exactly functions as the main pivot of the whole system then? Doesn' it look really like a kind of virtual-pivot system instead? Trying to see how the whole combination of linkgs work/moves is rather hard for me in this case....too many links!

    Regards,


    I took your picture and tried to explain it for you. I can tell you from experience that it works very well.


  18. #18
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    I have an 08 khyber. I like the feel of the bike quite a bit. The rear suspension design works very well. I have an X-fusion 02Rl dual chamber rear shock that allows for ramp up adjustability, and the addition of the dual chamber ramp up controll adds to the bottomless feel of the suspension. It does remain active under braking, but I have not ridden the other designs that claim to be the best at keeping the suspension active under braking like giants VPP 2 or whatever the newest incarnation is called, or any of the other big names newest designs. However from what I have been told they are better... Now take that for what it is, because there is the whole mongoose stigma, and we are talking perception, something which is heavily influenced by what you want to see/feel and also the fact that everybody seems to think what they have is the best system. And hopefully it is the best system for them. Back to the point, I think the design and function has been explained well by previous posts, so all I will lend is that, it works. Plain and simple. Very little bob from pedaling, and good pedaling technique really helps this a lot, chain tension has no noticeable effect on the suspension, so if you can "pedal circles" rather than mash them, the design is just plain awesome. One of my favorite things is how easy it makes pedaling through rough rock gardens, it just feels so awesome to power through rough stuff, feel the suspension doing it's job. To elaborate, you don't feel the suspension moving as much as you feel a sense of seemingly uninterupted traction. And the folks who claim the freedrive climbs very well are telling the truth. I was impressed at the bikes ability to go uphill at such a portly weight. I can only imagine the teocali climbs even better since it is lighter.
    Go ride it, ride other stuff you are interested in, and buy what feels best to you and suits your riding style best. One thing about mongoose I like a lot is you will get more bang for your buck in the component spec. All those Wally world bikes that are sold help this cause... So everytime someone says "oh I have a mongoose too!" and it's a walgoose, thank them for helping your bike to be spec'd nicer than others in the same price range.
    Sorry for the long post!

  19. #19
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    Edited above in one place of each post to add "-like". This more accurately describes the similarity as I had intended to communicate, as acting much like a URT, possibly with some difference in braking action compared to a simple high pivot URT.

  20. #20
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    Wow. Politician's answer. If you didn't know anything about the suspension, why a wordy, bloated, inconsistent answer that proves you're only answering for the sake of answering and sounding intelligent?
    Last edited by glitz; 03-27-2010 at 02:14 AM.

  21. #21
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    A unified rear triangle is not very similar to an isolated drive train really, derby.
    The URT tries to accomplish the same desired effect but falls short in several catagories. Isolated drive trains like freedrive, allow for a linkage based movement of the drivetrain whch is far better at keeping the suspension active while standing, braking, etc. URTs fall short there. It's just not as similar as you'd think. The linkage is key in the function and in it's ability to remain so active while keeping chain tension a non issue. The urt also stiffens way more when standing as well. Some like it, I don't. Freedrive works very well... Try it out... You'll see!

  22. #22
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    Quote Originally Posted by glitz
    Wow. Politician's answer. If you didn't know anything about the suspension, why a wordy, bloated, inconsistent answer that proves you're only answering for the sake of answering and sounding intelligent?
    Were you replying to me or derby? My answers show I obviously know SOMETHING about suspension systems, old and new. I am no pro for sure, but at least I offered helpful insight based on experiance riding the design! All you did was flame.
    So politicians answer.... Ok, you are less helpful than that, flamng troll answer helps nothing.

  23. #23
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    Replying to derby, of course.

  24. #24
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    Here's a video of the Teocali (2008) moving through its rear travel. This shows how the links move, including the little black one at the BB. One thing I noticed is that the axle path of the Teocali is purely recessional, which would help with ride quality. Most bikes that aren't URT's have some form of precession (axle moves forward) after a period of recession (axle moves backward). Since bumps try to move the axle rearward, having recession helps with impact harshness over sharp inputs.

    Here's the video - make sure to choose the 480p option in the lower right of the play window.

    http://www.youtube.com/watch?v=w6VHDRAvlsc

    It's only 2.5 MB, so if anyone wants the actual AVI file, I can email it to you.

  25. #25
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    Very cool -- thanks for posting.

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