Falling spring ratio v progressive spring ratio
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The rate or resistance is relative.lukee said:
In bikes and motorsports we usually call a spring that increases in resistance at a constant rate "linear".
Linear Rate Example: 1st inch of compression = 100 lbs, 2nd inch = 100+100=200 lbs, 3rd inch 100+100+100=300 lbs., etc.
Rising Rate Example: 1st inch of compression = 50 lbs, 2nd inch = 50+100=150lbs, 3rd inch 50+100+150=300 lbs., etc
Falling RateExample: 1st inch of compression = 150 lbs, 2nd inch = 150+100=250lbs, 3rd inch 150+100+50=300 lbs., etc.
Leverage from linkage will modify the rate of the spring. Around 360 degrees of rotating link leverage there are angles between two levers with a common pivot that are rising, then transition to falling, transition to rising, and falling again, and again, etc. every 45 degrees of usable range of pivoting leverage.
Combining rising and falling rates of linkage livers and springs (sometime springs are stacked with different rates) becomes more linear, with bias towards the stronger rate change at any moment. Rising plus rising becomes extremely rising, and vice-versa.
Rising rate gives a more compliant slow-speed compression (less resistance to pedal bob) and small bump compression and smooth deep travel big hit resistance. Falling rate gives less compliant slow-speed compression (more resistance to pedal bob) or small bump compression and less deep travel big hit resistance with more bottom out danger.
Damping modifies spring action rate too. Platform shocks add a short duration falling rate effect at the beginning of compression, and is better matched with more common rising rate net spring plus linkage leverage resistance.
- ray
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"falling rate" spring... connect 2 springs of different spring rates. pull. guess which stretches first.
example: wire together a ball point pen spring and a coil spring from your car. attach one end to your garage door and pull on the other. i'm going to go ahead and guess that the ball point pen spring stretchs flat while the auto coil spring looks on with a bemused smirk.
example: wire together a ball point pen spring and a coil spring from your car. attach one end to your garage door and pull on the other. i'm going to go ahead and guess that the ball point pen spring stretchs flat while the auto coil spring looks on with a bemused smirk.
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ray, how do you determine the rate of a linkage again? Is the only way to use a linkage software? thanksderby said:
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Rising rate is generally accepted as the best solution. It basically allows a softer spring rate to be used for a specific total suspension travel, giving better small bump compliance and improved bottoming resistance at the same time. The degree of rising rate is critical though. Too little has no significant effect and too much can limit travel and make the suspension feel harsh. You can achieve rising rate from geometry and progressive bump stops or a combination of both. Air springs are also inherently rising rate.
A linear suspension is not a bad thing, but there isn't much going for a falling rate suspension really.
A linear suspension is not a bad thing, but there isn't much going for a falling rate suspension really.
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It is possible to determine the rate of a linkage by simply looking at it. Of course this will only give you a rough idea of the overall rate, and is often very difficult to do.BanzaiRider said:
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I'm probably stupid but what do you look at exactly! haha I've taken out my shock a couple of times and cycled the suspension freely but I don't really see what defines the rate. Thanks.WheelieMan said:
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Visually, you need to see if the lever arm (usually a linkage activating the shock) is increasing or decreasing as you go through the travel. If lever arm is decreasing you have a rising rate. Lever arm increasing you have falling rate. No change it's linear.
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at a given point in the suspension's travel (start at full extension):
draw an imaginary line out from the seat stay linkage towards the main rocker pivot (a straight line through the center of the linkage parallel to the length of the linkage. if there isn't a linkage and the seat stay is directly connected to the rocker, then draw the line through the seat stay). this is the force vector. now draw a 90 degree line from that line to and through the center of the pivot. that's your wheel side lever, the length of the line connecting the force vector and the pivot.
on the shock side, draw the force vector out of the center of the shock in the direction of shock expansion and compression. draw a line 90 degrees to that line through the center of the main pivot. this is the shock side lever.
measure the length of each lever. now, depending on your perspective, you can divide the wheel lever by the shock lever or vice versa. for instance, to determine the leverage applied to the shock by wheel forces, you divide the wheel lever by the shock lever.
if you repeat this process for a number of points in the suspension's travel, you can draw a curve representing the leverage rate over the length of travel.
if you're still not clear on what a lever arm is, grab a wrench and put it on a suitable bolt. loosen the bolt by one of several ways; push on the wrench at a 90 degree angle. this is your maximum torque because all of the force you apply through your arm is being multiplied by the length of the wrench. now push on the wrench at a 45 degree angle. your resultant torque is much less because if you draw the line through your arm and the line 90 degrees through it and the bolt (the intersection will probably be at a point behind your wrist), that distance will be less than the length of the wrench. and because torque is force times the distance to the resisting object, the resultant torque is less.
draw an imaginary line out from the seat stay linkage towards the main rocker pivot (a straight line through the center of the linkage parallel to the length of the linkage. if there isn't a linkage and the seat stay is directly connected to the rocker, then draw the line through the seat stay). this is the force vector. now draw a 90 degree line from that line to and through the center of the pivot. that's your wheel side lever, the length of the line connecting the force vector and the pivot.
on the shock side, draw the force vector out of the center of the shock in the direction of shock expansion and compression. draw a line 90 degrees to that line through the center of the main pivot. this is the shock side lever.
measure the length of each lever. now, depending on your perspective, you can divide the wheel lever by the shock lever or vice versa. for instance, to determine the leverage applied to the shock by wheel forces, you divide the wheel lever by the shock lever.
if you repeat this process for a number of points in the suspension's travel, you can draw a curve representing the leverage rate over the length of travel.
if you're still not clear on what a lever arm is, grab a wrench and put it on a suitable bolt. loosen the bolt by one of several ways; push on the wrench at a 90 degree angle. this is your maximum torque because all of the force you apply through your arm is being multiplied by the length of the wrench. now push on the wrench at a 45 degree angle. your resultant torque is much less because if you draw the line through your arm and the line 90 degrees through it and the bolt (the intersection will probably be at a point behind your wrist), that distance will be less than the length of the wrench. and because torque is force times the distance to the resisting object, the resultant torque is less.
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If you're really interested, just measure it. Start by measuring the distance across the shock eyelets so you know the position of the suspension at full extension, then remove the shock. With the shock removed, position the suspension at the previously measured full extension. From this point simply compress the suspension 0.25" at a time (measured at the wheel) and note down the corresponding shock movement. Repeat this process all the way through the travel and you'll end up with a curve of wheel movement against shock movement. The changing gradient of this curve defines whether it's linear, rising or falling rate.BanzaiRider said:
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Thanks guys (uktrailmonster, drunkle and All Mountain), this should occupy my spare time tonight!!! I'll try to figure it out and probably come back with more questions as I'm quite bad with mechanics/physics stuff...uktrailmonster said:
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Leverage Ratioe
BazaiRider
Your leverage ratio starts at about 3:1 then drops to about 2.7:1 by my calc's. This isn't a very drastic drop compared to some of the other multi-linkage bikes. I suspect you definately use your travel.
Hence, yours is a rising rate design. Judging by the pivot locations there should be minimal chain extension, and a axle path back a bit (~5mm guessing at 50mm extension) then forward by about the same. This should be reasonably 'straight' axle path.
Someone please correct me if I'm wrong as I didn't have much time.
BazaiRider
Your leverage ratio starts at about 3:1 then drops to about 2.7:1 by my calc's. This isn't a very drastic drop compared to some of the other multi-linkage bikes. I suspect you definately use your travel.
Hence, yours is a rising rate design. Judging by the pivot locations there should be minimal chain extension, and a axle path back a bit (~5mm guessing at 50mm extension) then forward by about the same. This should be reasonably 'straight' axle path.
Someone please correct me if I'm wrong as I didn't have much time.
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Assuming your Banzai is the same bike as the new Remix (looks like it is to me), it appears that your bike has a rising rate throughout the first 2/3 of the travel. In the last 1/3 the suspension becomes falling rate. This can easily be seen by examining where the angle between "a line drawn between the rocker pivot and moving shock pivot, and a line drawn between both shock eyelets" becomes 90 degrees. After this point (obtuse angle) the suspension becomes falling rate. Of course this is a rough approximation as the angle between the seatstay and chainstay, and the angle between the seatstay and rocker also effect rate slightly in this situation.
(PS. Some might argue that "rising rate" is not the correct term to describe the curve in the first 2/3 of the travel, but it is the word that I feel is best. The semantics of suspension terms can get extremely confusing.)
(PS. Some might argue that "rising rate" is not the correct term to describe the curve in the first 2/3 of the travel, but it is the word that I feel is best. The semantics of suspension terms can get extremely confusing.)
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So what would they call it then?WheelieMan said:
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Well in my opinion, "rising rate" describes a suspension that becomes harder to compress as the bike goes through the travel. Doesn't matter if it becomes progressively harder to compress, or "regressively" harder to compress.uktrailmonster said:
I'm not sure how else to describe that sort of shock rate.
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It does matter, because eventually that "regressive" rate becomes falling rate. It depends on the travel of whatever bike, but since the regressive rate is a curved line, it will eventually turn downwards. So a bike could be "progressive" during the beginning of the travel, and then falling-rate near the end. It would ride kind of funny, but this is one problem that people run into when they put longer-stroke shocks on their bikes than were intended, although a couple bikes have rates regressive rates that turn into falling rates because they were simply designed this way. The VPP10 is a good example, starts off as progressive, the the curve levels off, and then it goes back down. They expect the progressiveness of the shock to offset this.WheelieMan said:
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