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  1. #1
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    Four-bar vs Faux-bar

    I recently read an article in a British MTB mag about different types of full suspension. They break full suspensions into 5 groups:

    1. Single pivot - Orange
    2. Four-bar - Horst link on chainstay, isolating suspension from pedalling / braking
    3. Faux-bar - Pivot is above dropouts on the seatstay, behave like single pivot bikes.
    The linkages are there to help drive the shock.
    4. VPP - Blur, Spider
    5. Floating drivetrain - GT i-drive, Maverick

    I had not previously encountered the term "faux-bar suspension". I was wondering if any of the suspension gurus on mtbr could elaborate on the differences between four-bar and faux-bar suspensions. Thanks.
    Kokopelli Racing

    "Curb drops to flat, or curb drops to transition? There's a BIG difference there." Qfactor03

  2. #2
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    Axle on a floating link vs swingarm

    Quote Originally Posted by yangpei
    I recently read an article in a British MTB mag about different types of full suspension. They break full suspensions into 5 groups:

    1. Single pivot - Orange
    2. Four-bar - Horst link on chainstay, isolating suspension from pedalling / braking
    3. Faux-bar - Pivot is above dropouts on the seatstay, behave like single pivot bikes.
    The linkages are there to help drive the shock.
    4. VPP - Blur, Spider
    5. Floating drivetrain - GT i-drive, Maverick

    I had not previously encountered the term "faux-bar suspension". I was wondering if any of the suspension gurus on mtbr could elaborate on the differences between four-bar and faux-bar suspensions. Thanks.
    Do a text search in mtbr. There are many uses of faux-bar discussions.

    So called Faux-bar has a physical monopivot swingarm determining the path of the axle to the frame. Four-bars have 2 swing arms from the frame connected to a "floating" link and the axle's path to the frame is determined by the paths of all the links not just one swing link.

    VPP's are also 4-bars but with very short swing links between the frame and floating link (or floating rear triangle).

    With floating axle 4-bars the rates of path curve and associated force tensions are sometimes tuned to be non-circular when using shorter swinglinks, such as the VPP's slightly "s" shaped path, while all monopivot swingarms have a circular paths with the frame.

    Your really must ride various designs to get a good sense of the subtle differences.

    - ray

  3. #3
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    The suspension "gurus" certainly can "elaborate" and have done so on countless threads in the past. The hardest part is wading through all the b*lls*it to actually learn anything useful.

  4. #4
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    Quote Originally Posted by uktrailmonster
    The suspension "gurus" certainly can "elaborate" and have done so on countless threads in the past. The hardest part is wading through all the b*lls*it to actually learn anything useful.
    well said......

    also be aware that many of these arguments will be based on theoretical arguments which while they may hold at that level, do not translate into a practical difference that will matter to you.

    also note that there are MANY parameters to how well a bike will ride for you, not just type of linkage. As I have said before, I could try to make a horst link bike and it would be a POS because the implementation would be the worst......would that imply that a horst linkage is not a good one?

    the ride of a bike is a multivariate equation if you will.....with many variable perhaps independently important, but when added to the equation along with the other important variables, may not matter so much and will often have interaction effects that become important..

    bottom line.....in my simple mind, if the implementations is solid based on virtually any common linkage, it can be a killer bike with its own pluses and minuses, subtle or otherwise.

    cheers

  5. #5
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    Why not a FAQ?

    I seriously think it's time to get a few FAQ threads on the topic! (e.g. one for Wheel path, and one for Shock linkages.)

    Also there's URT (unified rear triangle not common any more), Giant Maestro, DW-link, and Marin (whyte) linkages. Can't think of any others at the moment.

  6. #6
    Jm.
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    "Faux bar" is a faux term created by specializeds marketing department to make their suspension seem superior to anything else.

    A suspension system is either 4 bar or not, in other words it either has 4 components (linkage, main frame and two actuating rods (usually chainstay and seatstay) or it does not. It's just describing the parts. Pretty much any bike with a linkage is a 4-bar bike, becuase to make a linkage work you need 4 comoponents, hence the name 4-bar.

    A kona linkage-actuated single pivot is a 4 bar because there is the main frame, a chainstay, a seatstay (that actuates the linkage) and a linkage.

    A moto link bike like the Giant DH bike and Rocky Mountain RM series is 4 bar because there's the main frame, the swingarm, a pushrod, and a linkage. 4 parts.

    A horst link bike like a specialized is a 4 bar because there is a main frame, a chainstay, a seatstay driving the linkage, and a linkage.

    A VPP bike is a 4 bar because there is a main frame that constitutes one part, a rear triangle that constitutes another part, and two linkages, one of which drives the shock. Again, 4 parts.

    "Faux bar" is just a marketing term.
    I know in my heart that Ellsworth bikes are more durable by as much as double. AND they are all lighter...Tony Ellsworth

  7. #7
    The Ancient One
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    Quote Originally Posted by Jm.
    "Faux bar" is a faux term created by specializeds marketing department to make their suspension seem superior to anything else.

    A suspension system is either 4 bar or not, in other words it either has 4 components (linkage, main frame and two actuating rods (usually chainstay and seatstay) or it does not. It's just describing the parts. Pretty much any bike with a linkage is a 4-bar bike, becuase to make a linkage work you need 4 comoponents, hence the name 4-bar.

    A kona linkage-actuated single pivot is a 4 bar because there is the main frame, a chainstay, a seatstay (that actuates the linkage) and a linkage.

    A moto link bike like the Giant DH bike and Rocky Mountain RM series is 4 bar because there's the main frame, the swingarm, a pushrod, and a linkage. 4 parts.

    A horst link bike like a specialized is a 4 bar because there is a main frame, a chainstay, a seatstay driving the linkage, and a linkage.

    A VPP bike is a 4 bar because there is a main frame that constitutes one part, a rear triangle that constitutes another part, and two linkages, one of which drives the shock. Again, 4 parts.

    "Faux bar" is just a marketing term.
    I like "faux bar" because it's simple and mildly amusing. Otherwise you have to say "shock activating linkage" or "seat stay pivot linkage" as opposed to "chain stay pivot linkage" or "floating axle linkage" or some such.

  8. #8
    Jm.
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    Quote Originally Posted by Steve from JH
    I like "faux bar" because it's simple and mildly amusing.
    Well, I guess it's amusing, but I think of it like this;

    4-bar;
    Horst Link
    Single pivot
    Lawill
    VPP
    DW Link
    All other crap like Karpiel, Fulcrum, etc

    Monoshock;
    All designs like superlight, bullit, etc

    Other;
    Maverick and other stuff that does not easily go into one of the above catagories

    If you just want to make it easy on yourself, just call the Kona a single pivot 4-bar. It's simple, easy to understand, and doesn't use any wierd terms...
    I know in my heart that Ellsworth bikes are more durable by as much as double. AND they are all lighter...Tony Ellsworth

  9. #9
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    Best way to keep it simple:

    Ride a hard tail. I'm only half joking. I've been trying to convince myself to go FS for two years now, but everytime I get done with a test ride and jump from the FS back on to my HT and do the same loop, trail, or whatever, it always feels so much lighter and quicker that I end up deciding to keep the HT. Then, invariably, I get the bug again, decide I really want bike "X," "Y," or "Z" and start the process over again, always ending up disappointed with the test ride... Maybe if I threw my custom lightweight wheelset on the FS it would take care of the sluggishness (?). I really feel like I'm missing the boat or something, but when I compare them side by side, how can I argue with the evidence? BTW, I'm not talking about comparing to "lead sled" FS's either--the last one was a Racer-X 100 (although it had like 2.3 Kendas with tubes and a lot heavier components than I usually run...). I've decided I better wait until I can afford two bikes: my HT for most of what I ride and a 5" travel FS for the occasional shuttle ride (I'll be saving for a while...).

  10. #10
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    Faux-Bars are not Four-Bars

    Quote Originally Posted by Jm.
    "Faux bar" is a faux term created by specializeds marketing department to make their suspension seem superior to anything else.

    A suspension system is either 4 bar or not, in other words it either has 4 components (linkage, main frame and two actuating rods (usually chainstay and seatstay) or it does not. It's just describing the parts. Pretty much any bike with a linkage is a 4-bar bike, becuase to make a linkage work you need 4 comoponents, hence the name 4-bar.

    "Faux bar" is just a marketing term.
    Faux-Bars are not Four-Bars (and the term Faux-Bar is not just a marketing term). However, the bicycle community in general (marketing literature, magazines, web discussions, etc.) often uses the term "4 Bar" or "4 Bar Suspension" incorrectly to refer to any bicycle that uses a 4-bar linkage arrangement in the rear suspension (the Kona Dawg and Giant VT are examples of this incorrect usage). This leads to lots of confusion about this subject.

    Most of the people who take this stance will argue (as you have here) that since a Faux-Bar uses a four bar linkage it is a Four-Bar. This argument is absolutely incorrect (or at least it does not match the definition that has been in use for decades outside the mountain biking community). Whether or not a bike has a 4-bar linkage is not relevant, because those 4-bars (i.e. the 4 bars that make up the 4-bar linkage) are not the 4-bars we are talking about when we are talking about a 4-bar suspension.

    Those with a technical background (engineers in particular) seem to make this argument a lot. Maybe it's because most engineers instantly recognize that the seat tube, chainstay, seatstay, and rocker arms form a 4-bar linkage, and perhaps then they have erroneously deduced for themselves that that is why these bikes are called 4-bars. Although this argument does seem logical, it is simply not correct. The term Four Bar Suspension (or 4-bar for short) is well defined and has been used for decades outside the realm of mountain biking (in the automotive community for example) to describe a particular, well defined suspension configuration (defined long before the term was used to describe a bicycle suspension). A Faux-Bar suspension does not fit this definition, and therefore by definition is not a Four-Bar.

    Here are a couple of definitions:

    Four Link Suspension: A suspension system in which the axle housing (axle carrier) is connected to the chassis via 4 adjustable links. By adjusting the position and/or lengths of these 4 adjustable links you can adjust the location of the instant center (IC) of the rear axle.

    Being able to adjust the location of the IC can be an advantage for many reasons. For example, on a drag racing car the location of the IC determines how much weight is transferred to the rear tires during launch, so by adjusting the connection points and/or lengths of these 4 adjustable links, you can control how much traction you have during launch. It is these 4 adjustable links that we are talking about when we are talking about a Four-Link Suspension. Here is a picture of a Four-Link Suspension with the 4-links identified. You can see the various different mounting points for adjusting these 4 adjustable links. Note that these 4 links in and of themselves do not form a 4-bar linkage and note also that these 4-links do not correspond to the 4 bars that you have identified.


    .
    .

    Four Bar Suspension: A Four-Bar Suspension is equivalent to a Four Link Suspension, except that the 4 links are not adjustable (i.e. the location of the IC is fixed at design time).

    Most bicycle suspensions fall into the 4 bar category instead of the 4 link category because the 4 links (bars) are typically not adjustable. Here is a picture of a Four-Bar Suspension with the 4-bars identified. Note that these 4 bars do not form a 4-bar linkage and note also that these 4-bars do not correspond to the 4-bars that you have identified.


    .
    .
    For the skeptics out there (and to show that I have not invented this definition myself), here are a few web links that include the definition of a 4 link suspension (and a 3 link suspension - more on that later):

    http://www.olywa.net/rdsrfr/Air%20Li...t is a 4-link?
    http://www.mattsoldcars.com/techinfo/dictionary.shtml
    http://www.autoglossary.com/term_4.html
    http://www.off-road.com/prerocker/glossary.html
    .
    .

    Here is a picture of a typical Horst Link style Four-Bar. I have identified the 4 bars in the picture. Note that these 4-bars do correspond to the 4 bars in both pictures above, but that these 4-bars do not form a 4-bar linkage and that these 4-bars do not correspond to the 4-bars that you have identified. This bike is a Four-Bar.*


    .
    .

    The "4 Bars" we are talking about are the 4 bars that isolate the axle from the chassis. A Faux-Bar suspension does not have these 4 bars at all. This is why a Faux-Bar by definition is not a Four-Bar. In other words, on a Faux-Bar the axle carrier (in this case the chainstay assembly) is not isolated from the chassis by 4 Bars. Instead, the axle carrier is connected directly to the chassis (similar to a Ladder Bar suspension). It's commonly called a Faux-Bar because it looks like a Four-Bar even though it's not.


    .
    .

    I suppose you could argue that the mountain bike community has redefined the term "4-bar" to refer to any bicycle that uses a 4-bar linkage arrangement as a rear suspension system. Well, fair enough, but by this definition a hardtail with a Thudbuster seatpost would be a "4-bar". Is that really how you want to define the term "4-bar"? I would argue that common misuse of a term does not change the true definition of the term, especially when that term already has a well established definition. I also question the logic and reasoning behind redefining a term than has been used differently for decades.

    I like the term "Faux-Bar", because it draws a distinction between single pivot bikes that use a linkage to drive the shock and true four-bar designs. However, since there are many different types of four-bar bikes on the market (Horst, ICT, VPP, DW-Link, etc.) I think the term "Four-Bar" is much too vague and does lead to confusion because it is not used consistently (and the 3-bar discussion below makes it even more confusing). For these reasons, I guess I prefer to avoid using the term "Four-Bar" entirely, and try to use the terms Chainstay Pivot, Seatstay Pivot, VPP, DW-Link, etc. instead.
    .
    .

    * This is for the (observant) nitpickers that may have noticed that the chainstay assembly on the XCE shown above is physically not 2 links, rather it is 1 physical link. Does this make the XCE a "3 Bar" then? The answer is yes, technically it does (at least by the automotive definition). This is a common suspension configuration in the automotive community as well, where the upper (or lower) two links are combined into one link, forming a 3-Bar (or 3-Link) suspension. However, it is conceptually and functionally equivalent to a 4-bar.



    I hesitate to mention this here, because I think it may just confuse the issue. However, I think the fact that the name "3-Link Suspension" has nothing to do with a 3-bar linkage (it doesn't use 3-bar linkage at all) helps to illustrate the fact that the name "4-Bar Suspension" has nothing to do with whether or not it uses a 4-bar linkage (even though, coincidentally, 4-bar suspensions do use a 4-bar linkage).

    http://www.ffcobra.com/FAQ/3link.html
    http://www.auto-ware.com/shoptalk/3_4_lk.htm


    Apparently, not everyone in the mountain bike community is confused about this. Here is a "3-Bar Suspension" bicycle:


    .
    .

    To answer the original question. Four-Bar bikes and Faux-Bar bikes are visually very similar (well, at least Chainstay Pivot Four-Bar bikes are visibly similar to Faux-Bar bikes). However, conceptually they are very different. Conceptually, a Faux-Bar is a single pivot with a linkage that drives the shock. With a Faux-Bar, the IC (instantaneous center of rotation) and CC (center of curvature) of the rear axle are both fixed at the main pivot (as is the case with all single pivot bikes). With a Four-Bar suspension, the IC and CC can be placed anyplace in virtual space (thus the term VPP) and can move independently as the suspension cycles (the IC and CC don't even have to be physically located on the bike, and usually aren't).

    In regard to suspension design, there are many reasons that this may be an advantage. For example, the location of the IC has a large impact on how the bike behaves during braking. Being able to locate the IC anyplace in virtual space to help optimize braking performance is an advantage that Faux-Bar bikes do not have. However, that being said, in practice I think these differences are somewhat subtle and largely theoretical (at least when comparing chainstay pivot bikes and seatstay pivot bikes, I wouldn't necessarily say the same thing about other 4-bar bikes such as VPP, DW-Link, etc.). I have one of each (a Chainstay Pivot and a Seatstay Pivot), and I have yet to noticed any difference I could attribute to the location of the rear pivot (i.e. chainstay or seatstay). Then again, I don't charge into corners as hard and brake as aggressively as some do, so that may explain why I don't notice any difference (in other words, I'm not saying there isn't any difference, just that I don't notice any difference).
    Last edited by Backmarker; 01-04-2005 at 08:17 AM.

  11. #11
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    two bikes: my HT for most of what I ride and a 5~7" travel

    Quote Originally Posted by Chris2fur
    Ride a hard tail. I'm only half joking. I've been trying to convince myself to go FS for two years now, but everytime I get done with a test ride and jump from the FS back on to my HT and do the same loop, trail, or whatever, it always feels so much lighter and quicker that I end up deciding to keep the HT. Then, invariably, I get the bug again, decide I really want bike "X," "Y," or "Z" and start the process over again, always ending up disappointed with the test ride... Maybe if I threw my custom lightweight wheelset on the FS it would take care of the sluggishness (?). I really feel like I'm missing the boat or something, but when I compare them side by side, how can I argue with the evidence? BTW, I'm not talking about comparing to "lead sled" FS's either--the last one was a Racer-X 100 (although it had like 2.3 Kendas with tubes and a lot heavier components than I usually run...). I've decided I better wait until I can afford two bikes: my HT for most of what I ride and a 5" travel FS for the occasional shuttle ride (I'll be saving for a while...).
    know what you mean.
    HT for most of what I ride around in San Francisco Bay Area suits me well.
    If i lived around Lake Tahoe or Downieville I may want to expense of a good Turner coiled xs fs bike. I want a 6+" fs for the occasional shuttle rides or to check out DH races.

    for the price of one light xc fs disk bike $3000+ one could get one disk hardtail (Marin Pine Mountain steel $1300) and one fs disk (Kona Coiler $1600)

    me:
    I'll keep triming the weight off my steel hardtail without sacrificing performance & durability and buy the Coiler (or Stinky) when i'm ready.
    Last edited by TrailNut; 01-04-2005 at 12:25 PM.
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  12. #12
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    It's hard to believe that the geometry of that Turner and Rocky Mountain would be all that different since the only real difference is the location of one pivot (seat stay vs chain stay). Could it be argued that the chain stay is actually a better place for it since there's one less pivot to flex between the chassis and the axle? It's interesting to me that every successful off-road motorcycle design uses a single pivot instead of a 4-bar, and they're dealing with a LOT more torque and suspension loads than bicycles have to.

  13. #13
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    Different beasts...

    Quote Originally Posted by ElementRaceRider
    It's hard to believe that the geometry of that Turner and Rocky Mountain would be all that different since the only real difference is the location of one pivot (seat stay vs chain stay). Could it be argued that the chain stay is actually a better place for it since there's one less pivot to flex between the chassis and the axle? It's interesting to me that every successful off-road motorcycle design uses a single pivot instead of a 4-bar, and they're dealing with a LOT more torque and suspension loads than bicycles have to.
    Motorcycles have a heavy engine that delivers massive and continous amounts of torque. (and adds to a lower center of gravity) Bikes only have the rider, are scads lighter than motorcycles, and more importantly are driven by a very transient power stroke. In short a motorcycle only has to deal with bob once, when you hit the accelerator. A bike must fight bob with every pedal stroke.

    As for geometry, while tthe RM and the Turner have very similar apperances, slight differences in gometry can make a world of difference. Just drop you seat 2" or raise up you fork an inch, move you seat back an inch. It can change the ride dramatically depending on what you have and what you need. It's difficult to see the difference between a 73.5deg STA and a 71 deg STA , but you'll feel it the moment you try to climb something. Same with a HTA: 68.5 feels quite different than 70 but is only 1.5 degs different. The two angles (STA & HTA) together play a big role in defining the characteristis of a bike. So do pivot locations even in bikes of similar designs, move the main pivot just a little on a HL bike and it will feel like a different bike. Same goes for moving the HL, rocker angle, rocker length yatta.... Casual observation of a bike's layout gives very little information on how it will ride.

    As for lateral stiffness, pivot design and implementation has as much affect as linkage type. Turners are very stiff latterally because their pivots are designed to handle lateral loads very well. Even two bikes of similar linkage designs can be very different in stiffness if one does not implement the pivots well. Even if they both use the same kind of bearings.

    BTW, Backmarker, that's probably the most sensible, and practical clarification of 4-bar suspension I've seen, Thanks!
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  14. #14
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    Backmarker, that's a hell of a long winded way of explaining the difference between a 4-bar and faux link!! I do agree though. The big question is whether or not a virtual pivot point on a bike is a wothwhile advantage over a fixed pivot. I very much doubt it but I may be wrong. Your point about dragsters changing their IC to adjust weight transfer to the rear axle is incorrect though. The suspension geometry only affects the amount of squat in the suspension and the dynamic camber and toe angles of the wheels. A lot of people intuitively mistake increased suspension movement (particularly squat) for increased weight transfer. Weight transfer occurs due to acceleration and the amount is governed simply by the location of the centre of gravity and the wheelbase. A high CofG and a short wheelbase are what you require for increased weight transfer.

  15. #15
    Neg reppers r my biatches
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    Wow.....

    By the way, what do you call 10,000 engineers at the bottom of the ocean

    Cheers

  16. #16
    not so super...
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    and to bring back another favorite
    Attached Images Attached Images
    Nothing to see here.

  17. #17
    Neg reppers r my biatches
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    Quote Originally Posted by SSINGA
    and to bring back another favorite
    very nice...I'll keep that one

  18. #18
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    Jm seems to miss the point between a four bar linkage and four bar suspension.

    A kona for example is a four bar linkage, but it ain't four bar suspension. It's a monopivot, so we call it a faux bar.

    The differences, in a general nutshell a four bar squats less under acceleration, climbing and braking than a faux bar. This makes them feel crisper under power, stay more level when climbing and accelerating and bob less when running an open shock.

    Four bars can also have some awful bad habits if the designer doesn't get it right (e.g. GT LTS).

    The VPP, DW link, new giants, schwinn rockets, are all four bars.
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  19. #19
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    I was about to point out the same thing to Backmarker about weight transfer, but you beat me to it.

    I think there are real but small efficiency advantages in the way a four bar rolls over bumps. The argument is complicated but depends on positioning the instant center significantly ahead of the center of mass. That's only possible with a 4 bar when talking about a bicycle.

    This energy efficiency advantage wouldn't matter in motorsports. And you probably can't feel it directly. Indirectly it should show up in reduced times over the same course from the same rider effort or less rider fatigue from the same time over the same course. But there are so many variables here that it would be damned hard to prove.

    The only company I know of that tried to prove it, among other things, is Devinci of Canada. They experimented for a couple of years I think with an instrumented bike and tried lots of different pivot designs. They ended up opting for something close to the Ellsworth 4 bar design and are in fact licensing ICT from Ellsworth. They switched the Banzai model, their "all mountain" bike, from a faux bar to the new design.

  20. #20
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    Backmarker, you're really Zag, aren't you? This must be at least your fourth name change.

  21. #21
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    Quote Originally Posted by Steve from JH
    I was about to point out the same thing to Backmarker about weight transfer, but you beat me to it.

    I think there are real but small efficiency advantages in the way a four bar rolls over bumps. The argument is complicated but depends on positioning the instant center significantly ahead of the center of mass. That's only possible with a 4 bar when talking about a bicycle.

    This energy efficiency advantage wouldn't matter in motorsports. And you probably can't feel it directly. Indirectly it should show up in reduced times over the same course from the same rider effort or less rider fatigue from the same time over the same course. But there are so many variables here that it would be damned hard to prove.

    The only company I know of that tried to prove it, among other things, is Devinci of Canada. They experimented for a couple of years I think with an instrumented bike and tried lots of different pivot designs. They ended up opting for something close to the Ellsworth 4 bar design and are in fact licensing ICT from Ellsworth. They switched the Banzai model, their "all mountain" bike, from a faux bar to the new design.
    You're right, it's not really relevant to motorsport. As you say, there are a lot of variables making any theoretical efficiency gain difficult to prove or at least quantify. Personally I ride a Ventana X5 (lowly faux bar - LOL) but find it a very efficient bike due to its class leading rear lateral stiffness and low bearing stiction. Drawing a parallel with motorsport again, torsional chassis stiffness and suspension installation stiffness are both key factors and are ultimately more important than subtle suspension geometry changes. I've heard that Ventana stayed with the faux bar because Sherwood was not convinced he could justify the loss of rear triangle stiffness with a chain stay pivot. I suspect he may have a valid point. In any case, the X5 is a great ride and the transfer of torque through the rear triangle feels very direct. This attribute has also been commented on in several reviews of the bike. Other supposedly more sophisticated bikes I've tried have disappointed me with notable rear end flexing.

  22. #22
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    Quote Originally Posted by Bikezilla
    Motorcycles have a heavy engine that delivers massive and continous amounts of torque. (and adds to a lower center of gravity) Bikes only have the rider, are scads lighter than motorcycles, and more importantly are driven by a very transient power stroke. In short a motorcycle only has to deal with bob once, when you hit the accelerator. A bike must fight bob with every pedal stroke.
    I understand about the bob but with a motor bike there's always torque being applied, not just during initial acceleration. Then it gets reversed while braking, just as it is on a bicycle. If one of the advantages of a 4-bar design is maintaining suspension performance while braking why haven't any motorcycle designers seen it? That's all I was wondering.

    FWIW, every full suspension bike I've ever ridden bobs up and down to some degree when I pedal it, even the old URT designs. Not from chain torque but from me pushing my legs down/torso up. How could a suspension know the difference from gravity induced motion (bumps) and rider induced motion (pedaling)?

  23. #23
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    Quote Originally Posted by SSINGA
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  24. #24
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    Quote Originally Posted by ElementRaceRider
    I understand about the bob but with a motor bike there's always torque being applied, not just during initial acceleration. Then it gets reversed while braking, just as it is on a bicycle. If one of the advantages of a 4-bar design is maintaining suspension performance while braking why haven't any motorcycle designers seen it? That's all I was wondering.
    Motor bikes have all kinds of other things going on. Some actually have floating calipers, their shocks can be more sophisticated (up until recently anyway) there's a big whack of weight in the center of the bike that changes everything. Besides there are tons of different motor bike suspension designs, you'll have to be slightly more specific of which brand/design and application before saying it dosen't do what a bicycle does. I'm sure some do. Overall there is very little practical similarity between motorcycles and bicycles as far as suspension designs. The applications are very different.

    Quote Originally Posted by ElementRaceRider
    FWIW, every full suspension bike I've ever ridden bobs up and down to some degree when I pedal it, even the old URT designs. Not from chain torque but from me pushing my legs down/torso up. How could a suspension know the difference from gravity induced motion (bumps) and rider induced motion (pedaling)?
    Oh that's EASY! It can't, and it dosen't A good fully can dramatically reduce bob caused by pedal torque, but up and down body motion is still going to affect the suspension, there's no way to eliminate it uneless the suspension is partly locked out when the body downforce occurs. Some bikes like the VPPs create a stiffer suspension during pedal torque so you can stand and hammer and get less vertical mass induced bob. Some bikes have very good platform dampers that resist slow speed compression, which is just what body mass bob is. This can and does come at the expense of small bump and slow speed compliance. I've found the some shocks manage a very good partial workaroud by having speed sensitive damping which takes over if the bump compression exceeds a certain rate. Some take it a step further by having position sensitive damping as well so as it get further into the compression it increases damping to keep from blowing through the stroke even though it's very supple in the beginning. (In case you're wondering I'm thinking of the DHX here) I personally was very suprised to find how effective the DHX platform was even though it gave scant little up to small bump compliance.

    Now as for rider mass induced bob...well you might want to read some of Steve from JH's posts on the matter. He went through some interesting experiments to prove it does not have to effect efficiency, and may very well not.

    But I have to say a seatstay pivot bike does not have to lag behind a Horst link bike in the real world... Yetti and Ventana are clear examples. And a Horst link bike does not have to lag behind a seat stay pivot bike when it comes to lateral stiffness...Turner is a clear example of this. One does not have to be better than the other, it's all about how it's executed.
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  25. #25
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    The difference is small but real...

    A true 4-bar (Horst link...FSR, Turner) shines on the rough stuff when pedaling and braking. When climbing steep rough trails that require heavy pedal torque a Horst link's suspension does a better job at smoothing out the trail. It's the same with braking in the rough.

    Remember...it's still 95% rider.

    Mike

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