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  1. #1
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    New question here. Falling/Rising rate

    Is there any way to tell if an FS frame design is falling rate or rising rate (or linear for that matter) just by looking at it?? Ive searched MTBR using google but couldnt find any real info.. only things concerning what is better, where, why and how; of course it seems that there are various combinations and pros/cons.

    Any info or links would be greatly appreciated. Basically im just trying to fill my head with viable and actual mtb knowledge!

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    I don't think anybody can unless it's a simple single pivot like the Bullit.

    This software will do it http://www.bikechecker.com/ but you've got to be real careful when doing VPP and DWlink type bikes because a tiny error in pivot locations screws everything up.

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    Actually what i thought is that by looking at the movement of the moving end of the shock in relation to the fixed (on the frame) end it might be possible to deduct the 'rate' type.
    Maybe thats just part of the equation.. not sure at this point.

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    I guess it depends on what you mean by 'looking'. If 'looking' includes measuring how much the rear axle moves for each millimeter or so of compression of the shock stroke, then yes you can tell where the suspension rate rises and/or falls.

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    Quote Originally Posted by nybike1971
    I guess it depends on what you mean by 'looking'. If 'looking' includes measuring how much the rear axle moves for each millimeter or so of compression of the shock stroke, then yes you can tell where the suspension rate rises and/or falls.
    What your saying sounds like leverage ratio to me. Every suspension design has a leverage ratio regardless of falling/linear/rising rates.

  6. #6
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    The leverage ratio can change depending on where it is in the stroke of the shock. This is due to the design of the pivots and is what makes a given frame linear or rising or falling, or a mixture of these.

    The commonly quoted leverage ratio is an average over the whole length of the stroke.

    Typically you would want linear or rising. A falling rate will cause the bike to get more plush the deeper you are in the travel causing it to blow through the travel.

    Of course if the shock itself is not linear then that will complicate matters. i.e. A frame that has a falling rate could be coupled with a rising rate shock to produce a linear result. This is where you need to be careful when using air shocks on frames designed for coils and vice versa.

    Make sense? Or if I have anything wrong then please educate me.

  7. #7
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    Quote Originally Posted by PsyCro
    What your saying sounds like leverage ratio to me. Every suspension design has a leverage ratio regardless of falling/linear/rising rates.
    Rising rate means falling leverage ratio. Rate in this sense is differential movement of shock shaft divided by differential movement of the axle vertically. Higher rate means more shock shaft movement or a lower instaneous leverage ratio.

    Pretty confusing I know! I'm sure somebody will correct me if I stated that wrong.

    Here are a couple examples - SC Heckler (falling rate), and Turner 5-Spot (rising rate)
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    Well from what ive seen above so far, its not possible to tell just by looking. And it also seems that greater physics/suspensions knowledge is required to understand the topic at hand. I guess ill have to settle for accepting manufacturers info as i doubt anyone will be going into depth about this.. it would probably take up 10 posts!

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    Actually scratch that above. I just had another look at Danno's graphs. Starting to make more sense now. Still though it must be hard to 'visualize' the changing leverage ratio just by 'looking'.
    But i did realize that the suspension rate is tied to leverage ratio.. didnt see that before. Thats one step in the right direction at least!

  10. #10
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    I can tell by looking at some single pivots,(early marins where quite obviously falling) I dont find it too hard to visualise leverage rate at beginning and end of travel on most SPs, just by looking at the resultant angles , anything with links ...no, definately need paper and a few bits an bobs
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  11. #11
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    Quote Originally Posted by PsyCro
    Actually scratch that above. I just had another look at Danno's graphs. Starting to make more sense now. Still though it must be hard to 'visualize' the changing leverage ratio just by 'looking'.
    But i did realize that the suspension rate is tied to leverage ratio.. didnt see that before. Thats one step in the right direction at least!
    This may help a little more to show you where the wore 'rate' comes in. From this you can see why the Heckler is said to have a falling rate.

    The red line on this graph shows the rate (or gradient) for the Heckler. The rate numbers are basically 1/leverage ratio. If you look at the rate for the Heckler at zero travel it's ~.41 (guess eyeballing the graph). 1/.41 is about 2.4. 2.4 is the leverage ratio at zero travel.



    If you stare at this stuff for a while it makes perfect sense. Different rate curves are better for different types of riding. For trail riding I like the bike to be somewhat progressive (rising rate) because it'll be plush on the small stuff, but be able resist bottom out when doing drops. Jumping I actually like it to have a falling rate to give more 'pop' off the lip.
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  12. #12
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    Quote Originally Posted by PsyCro
    Is there any way to tell if an FS frame design is falling rate or rising rate (or linear for that matter) just by looking at it??
    Yes. Imagine two lines, the first from one shock mount to the other, and the second from the pivot of the shock linkage to the shock mount. If those lines form an acute angle approaching 90 degrees as the shock moves through its travel, it's a rising rate. Say the angle passes (or begins at greater than) 90 degrees and becomes increasingly obtuse, that's a falling rate.

    That can give you a general idea of the rate at any point in the travel and thus how the suspension behaves, for some frames anyway. Looking at the bike in front of me, which has separate linkage positions for coil and air, this suggests that the air position with a slightly acute angle is digressively rising initially, but quickly becomes a falling rate, with increasing leverage to counteract the air shock ramp up. The coil setting forms a much more acute angle and never reaches 90 degrees, suggesting that it is a rising rate throughout the travel, though increasingly less so.

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    Quote Originally Posted by fonseca
    Yes. Imagine two lines, the first from one shock mount to the other, and the second from the pivot of the shock linkage to the shock mount. If those lines form an acute angle approaching 90 degrees as the shock moves through its travel, it's a rising rate. Say the angle passes (or begins at greater than) 90 degrees and becomes increasingly obtuse, that's a falling rate.

    That can give you a general idea of the rate at any point in the travel and thus how the suspension behaves, for some frames anyway. Looking at the bike in front of me, which has separate linkage positions for coil and air, this suggests that the air position with a slightly acute angle is digressively rising initially, but quickly becomes a falling rate, with increasing leverage to counteract the air shock ramp up. The coil setting forms a much more acute angle and never reaches 90 degrees, suggesting that it is a rising rate throughout the travel, though increasingly less so.

    [SIZE=1]I'd better run and hide before derby replies with a dissertation on how completely wrong I am.[/SIZE]
    Let me know how that works out for a Nomad.

  14. #14
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    Quote Originally Posted by .Danno.
    Rising rate means falling leverage ratio. Rate in this sense is differential movement of shock shaft divided by differential movement of the axle vertically. Higher rate means more shock shaft movement or a lower instaneous leverage ratio.

    Pretty confusing I know! I'm sure somebody will correct me if I stated that wrong.

    Here are a couple examples - SC Heckler (falling rate), and Turner 5-Spot (rising rate)
    Those graphs don't include the rate of the spring. When adding spring rate to each using a linear coil the net "wheel rate" resistance to compression remains consistent with the “leverage” rate change during travel. But using a naturally rising rate air-spring shock will modify the wheel rate making the Turner increasingly rising in wheel rate overall. And the Heckler with an air shock become less falling in wheel rate than the "leverage" shows in the graph near sag and then deeper in travel the more extremely rising rate nature of the air-spring deeply compressed transitions the net wheel rate into rising wheel rate.

    Air chamber volume size and stroke differences vary the amount of rising air-spring rate too.

    It comes down to riding a bike and adjusting the suspension and rider fit carefully to the trail conditions being the best way to determine differences. Looking at parts of the suspension in isolation in comparison with other designs is interesting, but similarities or differences in isolated factors of the suspension can often be misleading when compared to riding time differences..
    Last edited by derby; 01-04-2008 at 03:24 PM.

  15. #15
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    Quote Originally Posted by derby
    Those graft show don't include the rate of the spring. When adding spring rate to each using a linear coil the net "wheel rate" resistance to compression remains consistent with the “leverage” rate change during travel. But using a naturally rising rate air-spring shock will modify the wheel rate making the Turner increasingly rising in wheel rate overall. And the Heckler with an air shock become less falling in wheel rate than the "leverage" shows in the graph near sag and then deeper in travel the more extremely rising rate nature of the air-spring deeply compressed transitions the net wheel rate into rising wheel rate.

    Air chamber volume size and stroke differences vary the amount of rising air-spring rate too.

    It comes down to riding a bike and adjusting the suspension and rider fit carefully to the trail conditions being the best way to determine differences. Looking at parts of the suspension in isolation in comparison with other designs is interesting, but similarities or differences in isolated factors of the suspension can often be misleading when compared to riding time differences..

    True, but looking at the mechanical characteristics of the frame certainly tells me what type of shock it will couple nicely with. Like you note that older Heckler blows through its travel pretty quickly with a coil, whereas the 5-Spot worked very poorly with the DHXair.

    You might as well factor in the type of damping too. A shock with progressive compression control valve like the 5th Element acts a lot different than a shimmed damper.


    Riding the bike tells the whole story, but if you know what you are looking for when you're in the market for a new frame this stuff can help you make the right choice. It's helped me...

  16. #16
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    Quote Originally Posted by .Danno.
    Let me know how that works out for a Nomad.
    Okay! And let me know when you read the phrase "for some frames".

    Obviously VPP, DW and other multi-pivot designs aren't applicable. I was trying to keep the verbiage to a minimum.

  17. #17
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    Quote Originally Posted by fonseca
    Okay! And let me know when you read the phrase "for some frames".

    Obviously VPP, DW and other multi-pivot designs aren't applicable. I was trying to keep the verbiage to a minimum.
    I bet you can't tell me what it would be on a Kona Stinky either. It has the same number of pivots as a VPP or DW link and each one of those pivots has an effect on the mechanical rate. That's why way back at the top of this thread I said "I don't think anybody can unless it's a simple single pivot like the Bullit.". VPP, DWlink, Horst Link, Faux Bar, etc are all the same to me and I can't tell what's happening just by looking at them.

    Single pivots with a shock linkage are the only kind of frames that I'd agree with you. On those it's simple geometry between the shock and the main pivot.

  18. #18
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    Quote Originally Posted by PsyCro
    Actually scratch that above. I just had another look at Danno's graphs. Starting to make more sense now. Still though it must be hard to 'visualize' the changing leverage ratio just by 'looking'.
    But i did realize that the suspension rate is tied to leverage ratio.. didnt see that before. Thats one step in the right direction at least!
    I remember asking the tech guy from KHS regarding this matter. In the case of the FR/AM 1500-2000 bikes, the 4 inch travel mode is a rising rate, the 5 inch travel mode is linear and the 6 inch travel mode is falling rate. If you noticed at the 5 inch travel option, the shock is perpendicular to the swing link while the angle becomes acute on the 6 inch and obtuse on the 4 inch mode. When I had that bike I remember I use to change springs when I change the travel due to the difference in leverage ratios for each mode as well.
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  19. #19
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    Quote Originally Posted by nickgto
    I remember asking the tech guy from KHS regarding this matter. In the case of the FR/AM 1500-2000 bikes, the 4 inch travel mode is a rising rate, the 5 inch travel mode is linear and the 6 inch travel mode is falling rate. If you noticed at the 5 inch travel option, the shock is perpendicular to the swing link while the angle becomes acute on the 6 inch and obtuse on the 4 inch mode. When I had that bike I remember I use to change springs when I change the travel due to the difference in leverage ratios for each mode as well.

    Well since this thread was active ive purchased the Linkage software and learned a few things about suspension in general. I also put my bike into the software and saw that all 3 positions (on my AM2000) are pretty much linear.. it does change a bit but not enough to make it rising or falling.

  20. #20
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    And...

    Levarge ratios...
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  21. #21
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    Stupid question but what do these curves say about initially setting up a bike, sag wise. That is, should a bike with a straight falling rate be set up differently sag wise than a bike with a straight rising rate? And does it say something about the type of shock to use (Air or coil)?

  22. #22
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    Quote Originally Posted by anand
    Stupid question but what do these curves say about initially setting up a bike, sag wise. That is, should a bike with a straight falling rate be set up differently sag wise than a bike with a straight rising rate? And does it say something about the type of shock to use (Air or coil)?
    Take a look about half way down this page, just below the calculator. It talks about your concerns. http://www.theride.ca/guru/spring-calc.htm

  23. #23
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    Quote Originally Posted by .Danno.
    Take a look about half way down this page, just below the calculator. It talks about your concerns. http://www.theride.ca/guru/spring-calc.htm
    Thanks, makes sense for the straight rates, but what would you do for a bike like that KHS shown about the kind of starts with a falling rate then goes back to a rising rate?

    Man, makes you realize that suspension design is more complicated then just Horst-link, VPP, single pivot or whatever else!

  24. #24
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    Quote Originally Posted by anand
    Thanks, makes sense for the straight rates, but what would you do for a bike like that KHS shown about the kind of starts with a falling rate then goes back to a rising rate?

    Man, makes you realize that suspension design is more complicated then just Horst-link, VPP, single pivot or whatever else!
    Those KHS rates are basically flat, there's almost no variation. Maybe PsyCro could put one of those on the same graph as a Nomad. You'd see a big contrast.

  25. #25
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    Quote Originally Posted by .Danno.
    Those KHS rates are basically flat, there's almost no variation. Maybe PsyCro could put one of those on the same graph as a Nomad. You'd see a big contrast.

    Yup, sorry did not look at the y-axis. Does not change more than a few %.

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