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  1. #1
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    Definition of Progressive Suspension

    I have been really trying to understand the definition of a progressive shock suspension (rear suspension) for some time, but I still don't think I understand it fully.

    What does a progressive suspension mean, compared to a linear suspension? Does it mean it's soft at the start, but gets harder at the end?

    What does it mean that a suspension 'ramps up' at the end? Ramps up meaning it is harder (or softer) at the end of its travel?

    Also, some rear suspension designs (ie. the suspension linkage design and not the rear shock) are defined as progressive. What does this mean? For such suspension designs, better to use a linear shock, or also a progressive shock?

    Also, some rear suspension designs have a falling leverage at the start, but rising after the midstroke towards the end. And some are rising at the start, but falling after the midstroke towards the end. What does this mean?

    And finally, what does it mean by a rear shock's 'leverage curve'? And in some of the leverage curve pictures, the Y-axis is names mm/mm. What does this mean and how to read this graph?

    Thanks in advance for the clarifications.
    Last edited by horriefic; 12-21-2010 at 05:39 PM.

  2. #2
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    Hmm.....no replies. I guess the majority of people are also not familiar with the terms above? To those who actually know what these terms mean, do post and share your knowledge for the benefit of the rest of the community. Thanks!

  3. #3
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    Quote Originally Posted by horriefic
    I have been really trying to understand the definition of a progressive shock suspension (rear suspension) for some time, but I still don't think I understand it fully.

    What does a progressive suspension mean, compared to a linear suspension? Does it mean it's soft at the start, but gets harder at the end?

    What does it mean that a suspension 'ramps up' at the end? Ramps up meaning it is harder (or softer) at the end of its travel?

    Also, some rear suspension designs (ie. the suspension linkage design and not the rear shock) are defined as progressive. What does this mean? For such suspension designs, better to use a linear shock, or also a progressive shock?

    Also, some rear suspension designs have a falling leverage at the start, but rising after the midstroke towards the end. And some are rising at the start, but falling after the midstroke towards the end. What does this mean?

    And finally, what does it mean by a rear shock's 'leverage curve'? And in some of the leverage curve pictures, the Y-axis is names mm/mm. What does this mean and how to read this graph?

    Thanks in advance for the clarifications.
    Its a tough thing to explain but I will give it a shot.

    A linear shock means that the amount of force needed to compress the shock is consistent line. Meaning if you were to look at a graph that showed how much a shock moves compared how much force is applied, the graph would show a straight line. This would be the red line on the little graph I made on paint in 5 seconds.

    On the other hand, A progressive shock means that the amount of force needed grows as the shock is compressed. The line would be curved, because the amount of force needed to compress the shock progressively grows as the shock compresses. This would be the blue line.



    Its a crude graph, But hopefully it gets the point across.

    Now a suspension ratio is how much the rear wheel travels compared to how much the shock moves. To get a leverage ratio, you take the rear wheel travel of a bike and divide it by the shock travel. So say you have a bike with 150mm of rear wheel travel and your rear shock has a 57mm stroke. You take 150mm and divide it by 57... giving you a leverage ratio of 2.63 : 1. So for every 1mm your shock moves, your rear wheel moves 2.63mm of its travel.

    Get it? Now, that describes a straight rate leverage ratio. A raising/falling rate ratio would mean that the ratio changes as the shock is compressed. Rising means the shock would ramp up at the end of its travel and a falling rate means it would drop off at the end. A rising rate shock would start off at say 3.0 : 1 and end at 2.5: 1 and falling would be the opposite. The numbers make it confusing since the rising rate ratio shrinks and falling rate ratio grows, but remember that the number means how much the wheel moves compared to the shock. The smaller numbers means shock has to move more to get the wheel to move. This means that the smaller number being at the end causes the shock to move more for a given amount of wheel travel causing it to ramp up, or rise at the end. Falling is the exact opposite.

    Rising rates are also considered progressive. and leverage ratios can change in many different ways, depending on the suspension design. Hopefully this helped and didnt confuse you.

  4. #4
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    From a Google search :

    All suspension systems resist compression more towards the bottom of the stroke (reaching full compression) than they do at the beginning of the stroke (when they are not compressed).

    Linear and non-linear suspension differ in the rate at which the resistence increases.

    Linear suspension will increase resistence at a steady pace. Hypothetical Example: For every 10 cm of shock compression the effort required to compress the shock will increase by 100 Newtons, regardless of how compressed the shock is.

    With Non-Linear ("progressive") suspension the amount of effort does not increase at a steady pace- instead it increases slowly at the beginning of the stroke, and much more rapidly near the bottom of the stroke. Using the last example: the effort required to compress the shock through the 1st 10cm may only by 50 Newtons, but the effort required to compress the shock through the last 10cm may be 300 Newtons. It gets progressively harder to compress the shock- thus the name.

  5. #5
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    Thanks for the post keen.

    mullen119, Thank you so much for taking the time and effort to make the post. It really gave me a much better understanding.

    On your diagram, assuming the x-axis is force, and the y-axis is travel, then the progressive shock takes a lot more force to get the shock to travel at the start, but once the line curves at the inflexion, it only takes comparatively less force for the travel to move quickly and bottom out. Am I reading this correctly? Or have I gotten the axis labelled upside down?

    Based on keen's explanation, where you need more force at the end to compress the shock an equivalent distance compared to the beginning, the blue line would need to be inverted. Or maybe, like stated above, my axes are labelled incorrectly?

    From a practical point of view, a rising rate shock that 'ramps up' at the end is better for peddling (as the shock moves comparatively less at the start of the travel), but gives a more plush and softer feel on drops right? (as the shock moves comparatively more ie. ramps up' at the end by travelling more).

  6. #6
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    Quote Originally Posted by horriefic
    On your diagram, assuming the x-axis is force, and the y-axis is travel,
    It's the other way around.

  7. #7
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    You have it backwards. X axis would be how far into the stroke you are and Y axis being how much force needs to be applied. All shocks, no matter if they are progressive or linear, need more force to compress them the farther they go into their travel. Like keen said, the difference is how the force is multiplied. Linear growing at a equal rate through out the shocks stroke, and progressive, the force growing at a multiplied rate as the shock moves through its stroke. Keens example is very good at describing this.

    Also, Rising rate(progressive) or linear do not have much of a effect on peddling from a shocks prospective. The difference is felt at the end of the shocks stroke, progressive being harder to bottom out because the force needed to compress the shock is much larger. In reality, the graph I made should have the blue line end higher on the Y axis then the red line. Where the lines would cross would be where the bottom out protection would start to be felt on a progressive rear shock.

  8. #8
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    This is a little better

  9. #9
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    Quote Originally Posted by horriefic
    Hmm.....no replies. I guess the majority of people are also not familiar with the terms above? To those who actually know what these terms mean, do post and share your knowledge for the benefit of the rest of the community. Thanks!
    Have you tried using search? Because all of this has been cover in depth before.

  10. #10
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    Thanks once again Mullen119. I appreciate it.

    One more question - If a bike's leverage ratio is rising eg. 3:1 to 2:1 (which means that the shock has to "move more for a given amount of wheel travel causing it to ramp up, or rise at the end."), would it be harder or easier to compress the shock at the end of the travel compared to a bike with a falling leverage ratio eg. 2:1 to 3:1, assuming a same shock is used on both bikes?

    My understanding is that a rising leverage ratio ie. a suspension that 'ramps up' at the end would imply that it is harder to compress the shock at the end. However, on the flipside, I imagine that a rising rate means that the shock moves more at the end, which means you only need to move the back tire up slightly to get the shock to compress in the same amount (compared to the beginning of the stroke), which would imply that it is easier to compress the shock at the end of the travel. So not sure of the answer.

  11. #11
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    Your correct in saying that its harder to move the wheel at the end of a rising ratio. The reason is the opposite of what you wrote. Take your 3:1 to 2:1 ratio. The shock has to do more work at 2:1 then it does at 3:1 for a given amount of travel. To move the rear wheel 3mm at the beginning of the stroke, the shock would only have to move 1mm. To move the rear wheel the last 3mm of travel, the shock would have to be compressed 1.5mm. Its going to take more force to move the shock 1.5mm then 1mm.

  12. #12
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    Everything is crystal clear now mullen119. I can now make sense of the the leverage ratio graphs, and can understand every post on suspension and leverage ratios discussions etc. Thanks to you! I am sure this thread will benefit many others. Happy riding!

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