High anti-rise makes the bike squat under braking forces. That puts you in quite a force on the spring, where it could feel harsh.
Low anti-rise...
High anti-rise makes the bike squat under braking forces. That puts you in quite a force on the spring, where it could feel harsh.
Low anti-rise buckles you to the front, where the suspension maintain it's ability to move with little force imputs. But you are being thrown to, or over, the handlebar.
Personally, I prefer high anti-squat, like single pivots.
I think its important to distinguish that the suspension isn't being forced apart by the anti-rise, but the wheel is being held back and the acceleration of your body weight is just tipping forwards which creates the extending moment. But otherwise its correct that sitting in the higher part of the travel where the spring rate is softer is generally beneficial. Again though it depends on setup, a soft, progressive bike with low anti rise will try to stand up a long way every time you touch the brakes but something a bit more linear with less sag might not be as noticeable.
I can't find a free link and haven't figured out a way to host safe file downloads but if you google "Influence of mountain bike riding velocity, braking and rider action on pedal kickback" it is a paper that the guys at Canyon wrote a few years ago while looking in to pedal kickback. Basically it mostly affects certain bikes at slow speed under heavy braking, I used the Enduro example above because it is a bike I have had someone describe the exact feeling of pedal kickback, without using the term and not really even knowing what it is!
The N6 AR starts at 95% and drops to -30% at full travel, moving from 80%-60% in the middle 1/3 of travel. The Levo AR starts around 60% and slowly decreases to around 51% at full travel. I'd try to explain difference in feeling that braking through small stuff (first half of travel), the N6 pitches forward less and feels more "taut", while the Levo feels more sponge-y. However the Levo maintains that feeling throughout the travel, while the N6 feels like the rear end becomes more active the harder you hit stuff.
High anti-rise makes the bike squat under braking forces. That puts you in quite a force on the spring, where it could feel harsh.
Low anti-rise...
High anti-rise makes the bike squat under braking forces. That puts you in quite a force on the spring, where it could feel harsh.
Low anti-rise buckles you to the front, where the suspension maintain it's ability to move with little force imputs. But you are being thrown to, or over, the handlebar.
Personally, I prefer high anti-squat, like single pivots.
I think its important to distinguish that the suspension isn't being forced apart by the anti-rise, but the wheel is being held back and the acceleration...
I think its important to distinguish that the suspension isn't being forced apart by the anti-rise, but the wheel is being held back and the acceleration of your body weight is just tipping forwards which creates the extending moment. But otherwise its correct that sitting in the higher part of the travel where the spring rate is softer is generally beneficial. Again though it depends on setup, a soft, progressive bike with low anti rise will try to stand up a long way every time you touch the brakes but something a bit more linear with less sag might not be as noticeable.
I can't find a free link and haven't figured out a way to host safe file downloads but if you google "Influence of mountain bike riding velocity, braking and rider action on pedal kickback" it is a paper that the guys at Canyon wrote a few years ago while looking in to pedal kickback. Basically it mostly affects certain bikes at slow speed under heavy braking, I used the Enduro example above because it is a bike I have had someone describe the exact feeling of pedal kickback, without using the term and not really even knowing what it is!
Dropbox? I sometimes use my personal dropbox with public links to share files...
Genuine Question 2: Has anyone ridden an O-chain and a freewheel crank (WRP/Intend) back to back?
Genuine Question 3: If you've ridden either, on a WC...
Genuine Question 2: Has anyone ridden an O-chain and a freewheel crank (WRP/Intend) back to back?
Genuine Question 3: If you've ridden either, on a WC style track (i.e. fast & no slow jank), is the effect of those products felt on the whole run or only felt in braking?
For me, I have a hard time believing those products actually produce a significant kinematic change to the bike. (Important: I'm not say they don't change the feel of the bike.) In my view they simply isolate the chain slap tugging on the pedals which intern makes the bike feel smoother. If there's less noise at the contact point, the rider can have a better feel for the grip at the tires. FYI, I do have an O-chain waiting to install and try, so I'm not knocking these products just curious of the group's perspective.
Spomer and I are working on a video that addresses this exact topic, because I was also really curious about if and how these things work. Video coming soon!
High anti-rise makes the bike squat under braking forces. That puts you in quite a force on the spring, where it could feel harsh.
Low anti-rise...
High anti-rise makes the bike squat under braking forces. That puts you in quite a force on the spring, where it could feel harsh.
Low anti-rise buckles you to the front, where the suspension maintain it's ability to move with little force imputs. But you are being thrown to, or over, the handlebar.
Personally, I prefer high anti-squat, like single pivots.
I think its important to distinguish that the suspension isn't being forced apart by the anti-rise, but the wheel is being held back and the acceleration...
I think its important to distinguish that the suspension isn't being forced apart by the anti-rise, but the wheel is being held back and the acceleration of your body weight is just tipping forwards which creates the extending moment. But otherwise its correct that sitting in the higher part of the travel where the spring rate is softer is generally beneficial. Again though it depends on setup, a soft, progressive bike with low anti rise will try to stand up a long way every time you touch the brakes but something a bit more linear with less sag might not be as noticeable.
I can't find a free link and haven't figured out a way to host safe file downloads but if you google "Influence of mountain bike riding velocity, braking and rider action on pedal kickback" it is a paper that the guys at Canyon wrote a few years ago while looking in to pedal kickback. Basically it mostly affects certain bikes at slow speed under heavy braking, I used the Enduro example above because it is a bike I have had someone describe the exact feeling of pedal kickback, without using the term and not really even knowing what it is!
Dropbox? I sometimes use my personal dropbox with public links to share files...
Yeah dropbox is OK but they recently changed their terms, so I'm working on some more permanent solutions for storage/sharing so I can have some decent repositories for the data & resources I have that won't get taken away or cost huge amounts of money in the long term
Genuine Question 2: Has anyone ridden an O-chain and a freewheel crank (WRP/Intend) back to back?
Genuine Question 3: If you've ridden either, on a WC...
Genuine Question 2: Has anyone ridden an O-chain and a freewheel crank (WRP/Intend) back to back?
Genuine Question 3: If you've ridden either, on a WC style track (i.e. fast & no slow jank), is the effect of those products felt on the whole run or only felt in braking?
For me, I have a hard time believing those products actually produce a significant kinematic change to the bike. (Important: I'm not say they don't change the feel of the bike.) In my view they simply isolate the chain slap tugging on the pedals which intern makes the bike feel smoother. If there's less noise at the contact point, the rider can have a better feel for the grip at the tires. FYI, I do have an O-chain waiting to install and try, so I'm not knocking these products just curious of the group's perspective.
Spomer and I are working on a video that addresses this exact topic, because I was also really curious about if and how these things work...
Spomer and I are working on a video that addresses this exact topic, because I was also really curious about if and how these things work. Video coming soon!
My estimate is this: Intend/WRP freewheel cranks have the same behaviour regarding the pedal-kickabck because freewheel is only moved elsewhere, but WRP si better asi it uses sprag clutch instead of ratchet and pawls. But it'll behave the same as freewheel in a rear wheel. Moreover, they cause worse shifting performance in no-pedalling mode as the chain is being pushed by locked rear wheel instead of pulled by crankarm. Once you start pedalling shifting gets normal.
OChain has huge play between starting to pedal and actually transmitting the torque on chainring.
High anti-rise makes the bike squat under braking forces. That puts you in quite a force on the spring, where it could feel harsh.
Low anti-rise...
High anti-rise makes the bike squat under braking forces. That puts you in quite a force on the spring, where it could feel harsh.
Low anti-rise buckles you to the front, where the suspension maintain it's ability to move with little force imputs. But you are being thrown to, or over, the handlebar.
Personally, I prefer high anti-squat, like single pivots.
I think its important to distinguish that the suspension isn't being forced apart by the anti-rise, but the wheel is being held back and the acceleration...
I think its important to distinguish that the suspension isn't being forced apart by the anti-rise, but the wheel is being held back and the acceleration of your body weight is just tipping forwards which creates the extending moment. But otherwise its correct that sitting in the higher part of the travel where the spring rate is softer is generally beneficial. Again though it depends on setup, a soft, progressive bike with low anti rise will try to stand up a long way every time you touch the brakes but something a bit more linear with less sag might not be as noticeable.
I can't find a free link and haven't figured out a way to host safe file downloads but if you google "Influence of mountain bike riding velocity, braking and rider action on pedal kickback" it is a paper that the guys at Canyon wrote a few years ago while looking in to pedal kickback. Basically it mostly affects certain bikes at slow speed under heavy braking, I used the Enduro example above because it is a bike I have had someone describe the exact feeling of pedal kickback, without using the term and not really even knowing what it is!
Dropbox? I sometimes use my personal dropbox with public links to share files...
Neko did a video early in his series, using data it showed he had a slight change in dynamic sag while testing with and without oChain.
I have done back to back, before I had data and could "feel" a difference in my feet, this was on a Trek Session that has a mid pivot idler. From that point on, I use it. I also ride flat pedals, so it make me more confident on the connection to pedals with much less feeling that my feet are sliding forward in square edge hits. I'm normally in a 6 degree setting and using a 6 degree POE hub.
To say this device has a "kinematic" change would be a stretch to prove. But doing a test with and without a chain might be more significant.
There was a question about mullet yokes on an Enduro in tech rumors so figured I'd drop something in here that is related that it brought to the front of my mind. When looking at leverage curve, there are a few things you can plot leverage as a function of that make sense: wheel position (vertical in travel), shock stroke, and total length of shock and shock yoke (if it has a yoke). For my purposes I'm usually doing shock stroke because I'm not playing with overall length of shock or shock yoke as a variable. When it comes to considering that as well, plotting leverage ratio as a function of total shock length including a yoke kind of helps things come together. Looking at it this way, a longer yoke or longer eye-to-eye shock doesn't actually have a different leverage curve so much as it sits in a different portion of the leverage curve. The image below is an example of this based on a 230x65mm shock with the option of making it a 236x65mm shock to correct geo for a 27.5 rear wheel. With the 230mm shock, the suspension is working in the range between the two green lines. with it changed to 236mm, it is now working between the two red lines. Most of the leverage curve for these two set ups (the area shaded green underneath), overlap. So it's almost more like you are trimming one end of the curve and adding to the other when you install a longer yoke or increase the eye-to-eye of the shock. This is the case for any change to shock length or yoke length.
There was a question about mullet yokes on an Enduro in tech rumors so figured I'd drop something in here that is related that it brought...
There was a question about mullet yokes on an Enduro in tech rumors so figured I'd drop something in here that is related that it brought to the front of my mind. When looking at leverage curve, there are a few things you can plot leverage as a function of that make sense: wheel position (vertical in travel), shock stroke, and total length of shock and shock yoke (if it has a yoke). For my purposes I'm usually doing shock stroke because I'm not playing with overall length of shock or shock yoke as a variable. When it comes to considering that as well, plotting leverage ratio as a function of total shock length including a yoke kind of helps things come together. Looking at it this way, a longer yoke or longer eye-to-eye shock doesn't actually have a different leverage curve so much as it sits in a different portion of the leverage curve. The image below is an example of this based on a 230x65mm shock with the option of making it a 236x65mm shock to correct geo for a 27.5 rear wheel. With the 230mm shock, the suspension is working in the range between the two green lines. with it changed to 236mm, it is now working between the two red lines. Most of the leverage curve for these two set ups (the area shaded green underneath), overlap. So it's almost more like you are trimming one end of the curve and adding to the other when you install a longer yoke or increase the eye-to-eye of the shock. This is the case for any change to shock length or yoke length.
Thanks so much! I'll try and crank up the damping.
@CascadeComponents I was reading your post about the Enduro mullet yoke yesterday in the Tech Rumors thread and what you were saying regarding the non linear change in damping got me thinking about how significant the impact of the reduced shock compression speed would be on the adiabatic spring rate if they were running an air shock. What are your thoughts on this?
I should add that the only thing I know about adiabatic spring rates is that they exist ha!
@CascadeComponents I was reading your post about the Enduro mullet yoke yesterday in the Tech Rumors thread and what you were saying regarding the non linear...
@CascadeComponents I was reading your post about the Enduro mullet yoke yesterday in the Tech Rumors thread and what you were saying regarding the non linear change in damping got me thinking about how significant the impact of the reduced shock compression speed would be on the adiabatic spring rate if they were running an air shock. What are your thoughts on this?
I should add that the only thing I know about adiabatic spring rates is that they exist ha!
Take this with a grain of salt because this is a generic spring curve I came up with for an air can. To make the impact of leverage ratio very apparent, this is comparing a 170mm bike that is 30% progressive to a 170mm bike that is 60% progressive. The 30% line happens to be a V2 Megatower. The 60% line is a crazy progressive V2 Megatower. In all cases I am comparing a set up with equal amounts of sag. To be clear that would be crap because the spike at end of travel is unreasonable, but the exaggerated impact makes the trend easier to see. Leverage curve plot below.
First one here is a comparison with no volume spacers. The higher shock pressure required to get the same sag results in higher shock force from top of travel to full compression. No surprises there.Wheel force is broken into two graphs so that the start of travel doesn't get overshadowed by the crazy spike at end of travel. Less force at wheel before sag point and then more force at all points after that. I know it doesn't look like much, but you can definitely feel that difference in the first half of travel.
Now we have the comparison with volume spacers on the less progressive set up to give them similar bottom out resistance. This changes the spring force curve so that the volume spacer set up is now generating a higher shock force near bottom of travel.
The impact on force at the wheel is that the force is really quite similar for a good portion of travel. There is so much overlap that I'm just going to do the wheel force curve for full travel. The last 1/3 of travel is where the difference really is apparent. The volume spacer wheel force goes a hair higher before falling back below again. For the fun of it I also threw in a coil comparison (green curve).
@CascadeComponents Thanks for that response! Specifically, what I’m wondering is if the enduro from that post might feel less poppy because, with the higher leverage ratio/lower motion ratio, the adiabatic spring rate would be lower for the compression speeds that the bike normally sees.
In your first graph, at 30% sag, the shock would be moving about 6% slower (if I did my math right) on the more progressive leverage rate curve than the less progressive curve. If the shock on the more progressive curve compresses slower I would assume the adiabatic spring rate be lower for a given compression speed, making the bike feel less poppy right? Will this be offset by the higher pressure they’d being running to maintain the same sag percentage? I have no idea but it was just something that popped into my head when I read that.
@CascadeComponents Thanks for that response! Specifically, what I’m wondering is if the enduro from that post might feel less poppy because, with the higher leverage ratio/lower...
@CascadeComponents Thanks for that response! Specifically, what I’m wondering is if the enduro from that post might feel less poppy because, with the higher leverage ratio/lower motion ratio, the adiabatic spring rate would be lower for the compression speeds that the bike normally sees.
In your first graph, at 30% sag, the shock would be moving about 6% slower (if I did my math right) on the more progressive leverage rate curve than the less progressive curve. If the shock on the more progressive curve compresses slower I would assume the adiabatic spring rate be lower for a given compression speed, making the bike feel less poppy right? Will this be offset by the higher pressure they’d being running to maintain the same sag percentage? I have no idea but it was just something that popped into my head when I read that.
Spring rate isn't really going to vary due to compression speed. The common example of a process that's assumed to be adiabatic is compression in the cylinder of an engine, which can be on the same order of magnitude as a bullet. You'd be hard pressed to create a leverage curve that was so different than heat transfer during compression was notably different between the two. That's not to say heat doesn't impact air shocks, though. Heat building up over time is very real though. Even on a 3min lap during the wet season by the time I'm at the bottom the air can is dry.
Pop on jumps usually goes hand in hand with mid-stroke support. As you roll up a lip centripetal force plus whatever preload you want to add with your legs compresses things similar to what you'd see in a big berm. Shock speeds are quite slow and on a well built jump with a long enough lip you pretty much compress to a certain point in travel and no more. In this case the shock is neither compressing nor rebounding by the time you get to the lip so spring force as felt at the wheel is the primary factor. Pop in terms of the bike's tendency to bounce into the air after hitting a root or rock where it's more of a bump jump is a combination of support from the spring and compression damping biased one way or the other depending on how hard you smash into it. Damping force can easily be higher than spring force for this one though.
I've actually spent a fair bit of time on the Enduro in both a 29/29 configuration and 29/27.5. I found geo followed by damping were the biggest differences between the two. Damping can be adjusted out at least.
Spring rate isn't really going to vary due to compression speed. The common example of a process that's assumed to be adiabatic is compression in the...
Spring rate isn't really going to vary due to compression speed. The common example of a process that's assumed to be adiabatic is compression in the cylinder of an engine, which can be on the same order of magnitude as a bullet. You'd be hard pressed to create a leverage curve that was so different than heat transfer during compression was notably different between the two. That's not to say heat doesn't impact air shocks, though. Heat building up over time is very real though. Even on a 3min lap during the wet season by the time I'm at the bottom the air can is dry.
Pop on jumps usually goes hand in hand with mid-stroke support. As you roll up a lip centripetal force plus whatever preload you want to add with your legs compresses things similar to what you'd see in a big berm. Shock speeds are quite slow and on a well built jump with a long enough lip you pretty much compress to a certain point in travel and no more. In this case the shock is neither compressing nor rebounding by the time you get to the lip so spring force as felt at the wheel is the primary factor. Pop in terms of the bike's tendency to bounce into the air after hitting a root or rock where it's more of a bump jump is a combination of support from the spring and compression damping biased one way or the other depending on how hard you smash into it. Damping force can easily be higher than spring force for this one though.
I've actually spent a fair bit of time on the Enduro in both a 29/29 configuration and 29/27.5. I found geo followed by damping were the biggest differences between the two. Damping can be adjusted out at least.
Air springs are absolutely affected speed/frequency and adiabatic compression, especially going from very low speeds around 5mm/s up to 75mm/s. This plot is of a DVO Topaz at 100psi and damper removed @ 25, 75, 125 and 254mm/s but didn't have a lower speed run which was a shame because the most change is at those very slow speeds. Bear in mind your shock is under 75mm/s around 50% of the time you are riding!
Also important to note that most spring testers use a fixed speed which is simultaneously too fast for pure isothermal compression but not fast enough to show much adiabatic effect either
One of the complicating factors is a higher leverage frame with a lower/softer wheel rate will allow for higher wheelspeeds which brings the damper speeds slightly closer to the lower leverage example, so its really tough to calculate all the different changes going on
Air springs are absolutely affected speed/frequency and adiabatic compression, especially going from very low speeds around 5mm/s up to 75mm/s. This plot is of a DVO...
Air springs are absolutely affected speed/frequency and adiabatic compression, especially going from very low speeds around 5mm/s up to 75mm/s. This plot is of a DVO Topaz at 100psi and damper removed @ 25, 75, 125 and 254mm/s but didn't have a lower speed run which was a shame because the most change is at those very slow speeds. Bear in mind your shock is under 75mm/s around 50% of the time you are riding!
Also important to note that most spring testers use a fixed speed which is simultaneously too fast for pure isothermal compression but not fast enough to show much adiabatic effect either
One of the complicating factors is a higher leverage frame with a lower/softer wheel rate will allow for higher wheelspeeds which brings the damper speeds slightly closer to the lower leverage example, so its really tough to calculate all the different changes going on
Impacted by heat and impacted by heat a significant amount are different things though. That's a pretty tight spread (looks like single digit percentage difference at bottom of travel) besides the slowest curve which looks like it could have something interesting going on with negative air spring crossover. When you look at how a bike like the Enduro with a mullet yoke would compare to a plain Enduro, the 6% increase in shaft speed is would be comparing 125 mm/s to 133 mm/s. You're going to have essentially the same curve. I would put money on the difference between 125 mm/s and 133 mm/s being less than the machine can accurately measure.
One thing that occured to me regarding progression is that one of the worst things for the bike frame and suspension hardware is the sudden shock loading during bottom out.
Simply but it places a sudden load on non movable parts.
In theory a more progressive suspension should reduce this type of loads, since the spring and damper are dispersing more of the load before bottoming out and slowing the impact at bottom out.
Am I thinking about this in the right way or totally off base (which is always a possibility)?
One thing that occured to me regarding progression is that one of the worst things for the bike frame and suspension hardware is the sudden shock...
One thing that occured to me regarding progression is that one of the worst things for the bike frame and suspension hardware is the sudden shock loading during bottom out.
Simply but it places a sudden load on non movable parts.
In theory a more progressive suspension should reduce this type of loads, since the spring and damper are dispersing more of the load before bottoming out and slowing the impact at bottom out.
Am I thinking about this in the right way or totally off base (which is always a possibility)?
Not off base at all. People often underestimate how much force you can momentarily put through your feet. Jumping and stomping on a surface can produce forces as high as 4,000 lbs. Bottoming out is a little different, but if you hit hard enough you can access momentary forces similar to stomping. That’s kind of the upper limit for your feet staying on the pedals. It would be interesting to put some strain gauges on a rampage bike and see how hard they push back on the pedals. If you absorb the impact over full travel exactly and don’t bottom harshly peak forces are always lower. So anyone who is bottoming out will impart lower peak forces on their bike if they switch to a more progressive setup. Anyone who is not using full travel will increase their peak forces since less travel is used to absorb an impact. Although without using full travel peak force is much lower and not at risk of breaking anything so long as the bike is well designed. All the frames I have seen break not including crashes have been from bottoming too hard. That’s also where I’ve seen cranks and bars go.
Anyone who has smashed shit with a hammer can identify with how rough it is on the bike to hit a harsh bottom out and shock load everything between your feet and the wheels.
I think its important to distinguish that the suspension isn't being forced apart by the anti-rise, but the wheel is being held back and the acceleration of your body weight is just tipping forwards which creates the extending moment. But otherwise its correct that sitting in the higher part of the travel where the spring rate is softer is generally beneficial. Again though it depends on setup, a soft, progressive bike with low anti rise will try to stand up a long way every time you touch the brakes but something a bit more linear with less sag might not be as noticeable.
I can't find a free link and haven't figured out a way to host safe file downloads but if you google "Influence of mountain bike riding velocity, braking and rider action on pedal kickback" it is a paper that the guys at Canyon wrote a few years ago while looking in to pedal kickback. Basically it mostly affects certain bikes at slow speed under heavy braking, I used the Enduro example above because it is a bike I have had someone describe the exact feeling of pedal kickback, without using the term and not really even knowing what it is!
My 2 newer bikes are a '22 Levo and a '23 Nomad 6. Here's the AR charts for them:
https://linkagedesign.blogspot.com/2023/06/santa-cruz-nomad-6-2023.html
https://linkagedesign.blogspot.com/2022/01/specialized-turbo-levo-2022…
The N6 AR starts at 95% and drops to -30% at full travel, moving from 80%-60% in the middle 1/3 of travel. The Levo AR starts around 60% and slowly decreases to around 51% at full travel. I'd try to explain difference in feeling that braking through small stuff (first half of travel), the N6 pitches forward less and feels more "taut", while the Levo feels more sponge-y. However the Levo maintains that feeling throughout the travel, while the N6 feels like the rear end becomes more active the harder you hit stuff.
Dropbox? I sometimes use my personal dropbox with public links to share files...
Spomer and I are working on a video that addresses this exact topic, because I was also really curious about if and how these things work. Video coming soon!
Yeah dropbox is OK but they recently changed their terms, so I'm working on some more permanent solutions for storage/sharing so I can have some decent repositories for the data & resources I have that won't get taken away or cost huge amounts of money in the long term
For now I think this dropbox link will work https://www.dropbox.com/scl/fi/uz1dvbh626xwq8o4t3xpj/Gerth2019_Article_InfluenceOfMountainBikeRidingV.pdf?rlkey=iiknu4km9zsh3u10xnxc97o9a&dl=0
My estimate is this: Intend/WRP freewheel cranks have the same behaviour regarding the pedal-kickabck because freewheel is only moved elsewhere, but WRP si better asi it uses sprag clutch instead of ratchet and pawls. But it'll behave the same as freewheel in a rear wheel. Moreover, they cause worse shifting performance in no-pedalling mode as the chain is being pushed by locked rear wheel instead of pulled by crankarm. Once you start pedalling shifting gets normal.
OChain has huge play between starting to pedal and actually transmitting the torque on chainring.
Neko did a video early in his series, using data it showed he had a slight change in dynamic sag while testing with and without oChain.
I have done back to back, before I had data and could "feel" a difference in my feet, this was on a Trek Session that has a mid pivot idler. From that point on, I use it. I also ride flat pedals, so it make me more confident on the connection to pedals with much less feeling that my feet are sliding forward in square edge hits. I'm normally in a 6 degree setting and using a 6 degree POE hub.
To say this device has a "kinematic" change would be a stretch to prove. But doing a test with and without a chain might be more significant.
There was a question about mullet yokes on an Enduro in tech rumors so figured I'd drop something in here that is related that it brought to the front of my mind. When looking at leverage curve, there are a few things you can plot leverage as a function of that make sense: wheel position (vertical in travel), shock stroke, and total length of shock and shock yoke (if it has a yoke). For my purposes I'm usually doing shock stroke because I'm not playing with overall length of shock or shock yoke as a variable. When it comes to considering that as well, plotting leverage ratio as a function of total shock length including a yoke kind of helps things come together. Looking at it this way, a longer yoke or longer eye-to-eye shock doesn't actually have a different leverage curve so much as it sits in a different portion of the leverage curve. The image below is an example of this based on a 230x65mm shock with the option of making it a 236x65mm shock to correct geo for a 27.5 rear wheel. With the 230mm shock, the suspension is working in the range between the two green lines. with it changed to 236mm, it is now working between the two red lines. Most of the leverage curve for these two set ups (the area shaded green underneath), overlap. So it's almost more like you are trimming one end of the curve and adding to the other when you install a longer yoke or increase the eye-to-eye of the shock. This is the case for any change to shock length or yoke length.
Thanks so much! I'll try and crank up the damping.
@CascadeComponents I was reading your post about the Enduro mullet yoke yesterday in the Tech Rumors thread and what you were saying regarding the non linear change in damping got me thinking about how significant the impact of the reduced shock compression speed would be on the adiabatic spring rate if they were running an air shock. What are your thoughts on this?
I should add that the only thing I know about adiabatic spring rates is that they exist ha!
Take this with a grain of salt because this is a generic spring curve I came up with for an air can. To make the impact of leverage ratio very apparent, this is comparing a 170mm bike that is 30% progressive to a 170mm bike that is 60% progressive. The 30% line happens to be a V2 Megatower. The 60% line is a crazy progressive V2 Megatower. In all cases I am comparing a set up with equal amounts of sag. To be clear that would be crap because the spike at end of travel is unreasonable, but the exaggerated impact makes the trend easier to see. Leverage curve plot below.
First one here is a comparison with no volume spacers. The higher shock pressure required to get the same sag results in higher shock force from top of travel to full compression. No surprises there.
Wheel force is broken into two graphs so that the start of travel doesn't get overshadowed by the crazy spike at end of travel. Less force at wheel before sag point and then more force at all points after that. I know it doesn't look like much, but you can definitely feel that difference in the first half of travel.
@CascadeComponents Thanks for that response! Specifically, what I’m wondering is if the enduro from that post might feel less poppy because, with the higher leverage ratio/lower motion ratio, the adiabatic spring rate would be lower for the compression speeds that the bike normally sees.
In your first graph, at 30% sag, the shock would be moving about 6% slower (if I did my math right) on the more progressive leverage rate curve than the less progressive curve. If the shock on the more progressive curve compresses slower I would assume the adiabatic spring rate be lower for a given compression speed, making the bike feel less poppy right? Will this be offset by the higher pressure they’d being running to maintain the same sag percentage? I have no idea but it was just something that popped into my head when I read that.
Spring rate isn't really going to vary due to compression speed. The common example of a process that's assumed to be adiabatic is compression in the cylinder of an engine, which can be on the same order of magnitude as a bullet. You'd be hard pressed to create a leverage curve that was so different than heat transfer during compression was notably different between the two. That's not to say heat doesn't impact air shocks, though. Heat building up over time is very real though. Even on a 3min lap during the wet season by the time I'm at the bottom the air can is dry.
Pop on jumps usually goes hand in hand with mid-stroke support. As you roll up a lip centripetal force plus whatever preload you want to add with your legs compresses things similar to what you'd see in a big berm. Shock speeds are quite slow and on a well built jump with a long enough lip you pretty much compress to a certain point in travel and no more. In this case the shock is neither compressing nor rebounding by the time you get to the lip so spring force as felt at the wheel is the primary factor. Pop in terms of the bike's tendency to bounce into the air after hitting a root or rock where it's more of a bump jump is a combination of support from the spring and compression damping biased one way or the other depending on how hard you smash into it. Damping force can easily be higher than spring force for this one though.
I've actually spent a fair bit of time on the Enduro in both a 29/29 configuration and 29/27.5. I found geo followed by damping were the biggest differences between the two. Damping can be adjusted out at least.
Thanks that's exactly what I wanted to know!
Air springs are absolutely affected speed/frequency and adiabatic compression, especially going from very low speeds around 5mm/s up to 75mm/s. This plot is of a DVO Topaz at 100psi and damper removed @ 25, 75, 125 and 254mm/s but didn't have a lower speed run which was a shame because the most change is at those very slow speeds. Bear in mind your shock is under 75mm/s around 50% of the time you are riding!
Also important to note that most spring testers use a fixed speed which is simultaneously too fast for pure isothermal compression but not fast enough to show much adiabatic effect either
One of the complicating factors is a higher leverage frame with a lower/softer wheel rate will allow for higher wheelspeeds which brings the damper speeds slightly closer to the lower leverage example, so its really tough to calculate all the different changes going on
Just found this paper that has some good tests though and a little bit more thorough than the one I pulled up. - https://www.sciencedirect.com/science/article/pii/S1877705810002961?ref=pdf_download&fr=RR-2&rr=82edf4048ef950a8
Impacted by heat and impacted by heat a significant amount are different things though. That's a pretty tight spread (looks like single digit percentage difference at bottom of travel) besides the slowest curve which looks like it could have something interesting going on with negative air spring crossover. When you look at how a bike like the Enduro with a mullet yoke would compare to a plain Enduro, the 6% increase in shaft speed is would be comparing 125 mm/s to 133 mm/s. You're going to have essentially the same curve. I would put money on the difference between 125 mm/s and 133 mm/s being less than the machine can accurately measure.
One thing that occured to me regarding progression is that one of the worst things for the bike frame and suspension hardware is the sudden shock loading during bottom out.
Simply but it places a sudden load on non movable parts.
In theory a more progressive suspension should reduce this type of loads, since the spring and damper are dispersing more of the load before bottoming out and slowing the impact at bottom out.
Am I thinking about this in the right way or totally off base (which is always a possibility)?
Not off base at all. People often underestimate how much force you can momentarily put through your feet. Jumping and stomping on a surface can produce forces as high as 4,000 lbs. Bottoming out is a little different, but if you hit hard enough you can access momentary forces similar to stomping. That’s kind of the upper limit for your feet staying on the pedals. It would be interesting to put some strain gauges on a rampage bike and see how hard they push back on the pedals. If you absorb the impact over full travel exactly and don’t bottom harshly peak forces are always lower. So anyone who is bottoming out will impart lower peak forces on their bike if they switch to a more progressive setup. Anyone who is not using full travel will increase their peak forces since less travel is used to absorb an impact. Although without using full travel peak force is much lower and not at risk of breaking anything so long as the bike is well designed. All the frames I have seen break not including crashes have been from bottoming too hard. That’s also where I’ve seen cranks and bars go.
Anyone who has smashed shit with a hammer can identify with how rough it is on the bike to hit a harsh bottom out and shock load everything between your feet and the wheels.
Post a reply to: Kinematics