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  1. #1
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    Can somebody explain high speed damping? (on forks)

    I sort of understand low speed compression damping. It is to help prevent brake dive and bobbing, as it gives a little bit of a platform feel. But I don't understand high speed compression damping. I know that it mainly occurs if you hit a big bump at high bike speeds, but I don't know whether you want a lot of it (perhaps to prevent bottoming) or a little of it to get more bump absorption and less shock transmitted to the hands. Should the (dyno) curve be steep or shallow, and what is the preload or y axis intercept? The only careful tuning I have done is on vehicle suspensions, and I know that in that case, I like a relatively linear curve (medium slope, low preload). If the curve is too digressive, the high initial slope makes small bump compliance feel bad. If there is too little high speed compression, the suspension also seems to get this rubbery feel.

    I sort of understand low speed rebound damping. It is to help prevent spring-back when you hit a big obstacle at slow bike speeds. But I don't understand high speed rebound damping. I know that it mainly occurs after you get launched off a rock or ride over a pothole, but again, I don't know what the ideal damping curve should be (for a given style of riding, ok?). The only careful tuning I have done is on vehicle suspension, and I know that in that case, if the curve is too digressive, you get this weird sensation where the car springs back quickly after a big dip, and then suddenly stops. It feels a little bit disconcerting, but maybe for bikes that is ok. It seems that digressive is the way to go to prevent "jacking down".

  2. #2
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    I only have a few minutes, so I can only post a few short things for now:

    High speed or low speed compression or rebound have nothing to do with bike speed, its about the speed at which the fork is compressing

    HSC is like a blow off of LSC. When oil cant flow through the LSC port fast enough, the HSC valve(usually shims) will open to allow more oil to flow. The more HSC you run, the less oil can flow during high shaft speed impacts.

    The more HSC you run, the more you will feel your fork(or shock) spike during high shaft speed impacts. This is caused by the oil not being able to flow past the compression piston fast enough and the fork/shock reaching the maximum shaft speed that the oil flow will allow.

    HSC can/is used to control bottom out. But can lead to the harsh spiking feel.

    There is no correct answer on how much to run, its all based on preferences. From my general experience, you want to run enough to keep high shaft speed impacts feeling under control, but without the spiking feeling you get from running to much.

    You mention preload. If you have a preloaded shim stack for a HSC circuit, its going to give a platform type feel when the LSC port is closed. Non preloaded shim stacks will always flow some oil, so no platform and a more linear damping curve would exist.


    For rebound, HSR is used to bypass LSR and help a fork/shock return to full travel fast enough to not pack up. Because the only force a rebound damper faces is the force of the spring pushing the fork/shock back to full travel, HSR generally happens deeper into the travel(higher spring pressure) while LSR happens at the beginning of the stroke(low spring pressure). This is not always the case, but its the general rule. Its also why LSR is often referred to as begging stroke rebound and HSR is referred to as ending stroke rebound.

  3. #3
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    Quote Originally Posted by mullen119 View Post
    High speed or low speed compression or rebound have nothing to do with bike speed, its about the speed at which the fork is compressing.
    Correct.

    Low speed shaft compression events:
    - Landing a jump
    - Braking
    - Big hits

    High speed shaft compression events:
    - Stutter bumps
    - Chipseal
    - Any small bump

    It's counter-intuitive, but generally the less your fork or shock moves as a result of a bump, the faster the shaft moves. The more the suspension moves, the slower the shaft moves.

    Friction primarily is felt in high shaft speed events. Thus, kashima forks nicer on all the small choppy stuff, but you're much less likely to notice on big hits.

  4. #4
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    Btw the spring-back mentioned in the first post is controlled by rebound damping. You can actually have high and low speed rebound damping, also, but no MTB fork or shock I've owned has it.

  5. #5
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    Quote Originally Posted by mullen119 View Post
    you want to run enough to keep high shaft speed impacts feeling under control
    What does this mean?

    Usually when I do fork tuning, I like to keep turning down both the compression and rebound knobs and the fork gets more plush, but then starts to feel wallow-ey and rubbery. Where do I add the damping back in?

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    Pretty much all rear shocks have a HSR circuit and lots of forks have it as well. Not many have an external adjustment for it though.

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    Yes, I was referring to an external adjustment for it. A 4-way adjustable shock or fork would have high and low speed compression and rebound.

    Beanbag: it means that if you don't have enough damping, the fork or shock will feel like a spring, which bounces several times per hit.

    Here's what I do to tune my suspension.

    1. set sag appropriately for the trail. make sure you are fully geared up-- water, camelbak, shoes, helmet, etc. if you want a firm ride, for a relatively smooth course or to optimize pedaling, set sag to 15-20%. if you want a more plush ride, and to ensure you use more travel, set sag to 25-30%. this is pretty easy with an air fork, but you might find that with a coil you can only set so much preload if you are light for the spring.

    2. turn the knobs all the way firm until they stop. all of them. now count each click as you turn them soft. now set the knobs in the middle if you're average weight, or 1-2 clicks firmer if you are heavier. (heavier riders use more spring rate, which requires more damping). 1-2 clicks softer if you're significantly below 170.

    3. find a test section to ride. some people use stairs as a quick guideline, but I don't think it can replace the feel of 1-2 miles of trail. make sure this test section has everything you need to test-- big hits, stutter bumps, hard braking.

    4. observe travel.
    bottomed out - add compression (preferred) or air, or reduce preload. if your fork or shock lacks compression adjustment then you may have to choose between appropriate sag and not bottoming out.

    5. DO NOT CHANGE MORE THAN ONE THING AT A TIME. the biggest mistake made when tuning is to change more than one setting at a time. you can easily get confused about what knob is responsible for what you like/dislike about the ride quality.

    6. test ride again and observe ride quality differences and travel. do this as much as you need to dial in your balance of bump absorption and travel.

    7. now pay attention to how the bike handles after landing a big jump and over little bumps. if it springs back too fast, add rebound damping. don't add too much or the suspension will wallow-- it won't return to neutral in time for the next bump.

    8. while it is fresh in your mind, write down (on paper or your smartphone) what your settings are and what trail you set them on. this is the second big mistake people make-- not writing down a known good setting, or if your tuning is incomplete, write down what you have so far and what you need to tune next. write down notes about how much travel you used, air pressure (or preload), and how many clicks on each knob.

    what are you tuning for-- what's the "right" final setting?
    obviously a lot of this is going to be personal preference. some people like the pedaling and handling of a stiffer suspension. others want maximum plushness, which works especially well if you have no drops or jumps on the trail. and a few like fast rebound, but I can't figure why.

    hope this helps!

  8. #8
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    Quote Originally Posted by ColinL View Post
    hope this helps!
    Thank you for taking the time to type that out. It DOES help.

    (a former Kansan, now transplanted to Maine)

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    Quote Originally Posted by ColinL View Post
    Yes, I was referring to an external adjustment for it. A 4-way adjustable shock or fork would have high and low speed compression and rebound.
    If it had HSR adjustment it would more than likely be a 5 way since preload adjustment is probably the most common adjustment any shock or fork has for any sport. Not trying to knit pick your post.

  10. #10
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    Thanks for the guide, but the knobs only influence low speed damping. I have the ability to take apart the damper and shuffle shims around.

  11. #11
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    Quote Originally Posted by beanbag View Post
    Thanks for the guide, but the knobs only influence low speed damping. I have the ability to take apart the damper and shuffle shims around.
    What fork do you have? A Manitou?

    What ride characteristics are you looking for?

  12. #12
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    minute pro

    plush and shock absorbing, with just enough platform until it starts affecting bump sensitivity.

    Actually, never mind what I want. Look back at post 5 and tell me what you think.

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    Looked at post 5. Instead of going through all the 8 steps I posted, let's shorten it a bit:

    If your sag is good, you need more compression and rebound damping. I would start with rebound, to see if maybe that's all you lack. Don't change them both at the same time. As you add compression, you will naturally lose some plushness. That's how it goes.

    If your sag isn't good, then do the whole enchilada.

  14. #14
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    Quote Originally Posted by kan3 View Post
    If it had HSR adjustment it would more than likely be a 5 way since preload adjustment is probably the most common adjustment any shock or fork has for any sport. Not trying to knit pick your post.
    For coils, sure. Air forks and shocks do not have preload. But yes, you're right, and long-travel coil is likely to be 5-way.

  15. #15
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    The never ending quest for Low Speed and High Speed damping force characteristics! Something we chase every day!

    The biggest problem I see with the understanding of how much and when for home tuners, and even a lot of suspension tuning companies, is that it takes a lot of equipment to actually understand what the fork or shock is doing.

    First part of the equation is understanding what the fork is doing during a specific event. For instance, when you hit the brakes at 15mph at what velocity is the fork moving. When you run over successive roots, when you run over successive roots during braking, when you hit a curb, etc. Without this information it's very hard to know what to change. This is where on-board data logging comes into play. Data loggers allow you to see the event and give you an understanding of the amount of travel, the velocities involved, and the amount of g-load being generated to better understand how much the chassis is moving(harshness).

    Armed with that information, you can then run the fork or shock on a suspension dyno to measure the amount of forces being generated. Make adjustments, re-run on the dyno to verify that you changed the point in the force curve that you meant to change, and then get back out on the trail. Rinse and repeat, and eventually you end up with the best overall compromise.

    I've attached a few screenshots from our data logging units and suspension dyno for your viewing pleasure.

    One note I will mention is that too broad of a range adjustable externally is generally not a great thing, except in the area of designs such as the CCDB. Generally speaking if you're getting a broad range externally than your force curve is too linear and is leaning to much towards a single port, or port orifice, damping system. This is great with out of the box suspension components, as the manufacture doesn't know who the end user will be, but not great for those experimenting and tuning at home. If your shimmed system is working efficiently, the external adjusters are generally controlling a small window of the force curve.

    Darren
    Attached Thumbnails Attached Thumbnails Can somebody explain high speed damping? (on forks)-travel-bottoming.jpg  

    Can somebody explain high speed damping? (on forks)-velocity.jpg  

    Can somebody explain high speed damping? (on forks)-dyno.jpg  


  16. #16
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    The fact you guys own a shock dyno and know how to use it certainly make me more likely to consider your tuning services.

  17. #17
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    Quote Originally Posted by beanbag View Post
    minute pro

    plush and shock absorbing, with just enough platform until it starts affecting bump sensitivity.

    Actually, never mind what I want. Look back at post 5 and tell me what you think.
    One thing to keep in mind is that there is a huge crossover between LSC and HSC adjustments. For example, if you use an extremely stiff HSC shim stack and keep the LSC fully open, the fork will still flow enough oil to feel pretty smooth overall. Same for the opposite. A weak shim stack with LSC full closed will still flow enough oil to allow the fork to move with fairly low restriction. This is something that is worse with damper designs like ABS+ and Mission Control. When tuning the fork, its best to keep in mind what setting you are likely to run your LSC at when picking a shim stack.

    Also, HSC events can happen on impacts that use any amount of travel. Jumps to transitions do tend to be more of a LSC event, while jumps to flat and drops to flat tend to be HSC events. Small bumps can also be either high or low speed events, mainly decided on the shape of the bump(square edged bumps tend to be HSC events and smaller rounded bumps and dips in the trails are LSC.


    As for what I meant by feeling under control. The best way I can describe it is to say you want the fork to feel that it uses the perfect amount of travel for any given compression. So if you land a jump and if feels like it spikes , then I would feel like there is too much compression and the fork should have used a little more travel to absorb the impact. If on the same jump, I feel like it blew through the travel and was diving, I would feel like I needed a little more. This is where having the proper spring rate is the first thing to set up and the most important. You dont want to confuse a diving fork as not enough damping when in fact its under sprung. Spring rate trumps all. damping is like fine tuning.

    Now the ABS+ damper, although slightly flawed by the cross over problem, is great for custom tuning and still one of the best fork dampers on the market. The reason is the dished piston. You have 3 choices for tuning. A highly preloaded shim stack that when the LSC is closed, gives a firm platform(generally for XC). A slightly preloaded shim stack that gives a slight platform(AM). Or no preload and no platform. (more for DH)
    Which style you choose depends on what you want. It sounds like you are looking for the middle ground AM style stack. As for which stack you choose, that depends on where you want to run your LSC. Thats why the dyno charts are so great. It really narrows the search for you.

    Hope that helps

    Edit: I'm glad darren chimed in. All of what I wrote is based off my personal experience which is extremely limited in comparison to his. If any of what I wrote is wrong, feel free to correct me Darren, Im still learning like most of us.

  18. #18
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    Quote Originally Posted by PUSHIND View Post
    The never ending quest for Low Speed and High Speed damping force characteristics! Something we chase every day!

    The biggest problem I see with the understanding of how much and when for home tuners, and even a lot of suspension tuning companies, is that it takes a lot of equipment to actually understand what the fork or shock is doing.

    First part of the equation is understanding what the fork is doing during a specific event. For instance, when you hit the brakes at 15mph at what velocity is the fork moving. When you run over successive roots, when you run over successive roots during braking, when you hit a curb, etc. Without this information it's very hard to know what to change. This is where on-board data logging comes into play. Data loggers allow you to see the event and give you an understanding of the amount of travel, the velocities involved, and the amount of g-load being generated to better understand how much the chassis is moving(harshness).

    Armed with that information, you can then run the fork or shock on a suspension dyno to measure the amount of forces being generated. Make adjustments, re-run on the dyno to verify that you changed the point in the force curve that you meant to change, and then get back out on the trail. Rinse and repeat, and eventually you end up with the best overall compromise.

    I've attached a few screenshots from our data logging units and suspension dyno for your viewing pleasure.

    One note I will mention is that too broad of a range adjustable externally is generally not a great thing, except in the area of designs such as the CCDB. Generally speaking if you're getting a broad range externally than your force curve is too linear and is leaning to much towards a single port, or port orifice, damping system. This is great with out of the box suspension components, as the manufacture doesn't know who the end user will be, but not great for those experimenting and tuning at home. If your shimmed system is working efficiently, the external adjusters are generally controlling a small window of the force curve.

    Darren
    I wish I could afford all that tech Trial and error is such a pain in the a$$.

  19. #19
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    As a visual, this is a link from the Roehrig website, kind of offers a visual into some of this discussion.

    http://www.roehrigengineering.com/Do...ear_shock2.wmv



    Related to the graphs posted by PUSH, Darren, one item I have never been able to grasp from tuners that do utilize data logging such as a Shock Clock and a Dyno, why is it that when data logs record events, the events reach values easily well above the dynos capability, how can the information be compared or valid?

    I ask, using your posted information, based on peak recorded compression events of over 2ms or approximately 80 inches per second, yet your dyno run sheet maxes out at 10 IPS illustrated with what appears to be a possible 22 IPS not selected. Granted these may not be related dampers or runs.

    Just curious how the difference between data logged at high IPS values can be compared to testing / building dampers at low IPS values.

    I am likely wrong but was taught that to properly evaluate and utilize the equipment, the dyno needed to have a capability to match the recorded events of the Shock Clock. Dyno testing at low IPS works well for smooth terrain, like pavement, but even Roehrig recommends seriously high IPS for off-road applications.

    Not bashing your equipment or what results you achieve, just curious how other shops and your shop validate or tune true HSC events on the dyno.

    PK
    Attached Thumbnails Attached Thumbnails Can somebody explain high speed damping? (on forks)-velocity.jpg  

    Can somebody explain high speed damping? (on forks)-dyno.jpg  

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  20. #20
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    Related to the graphs posted by PUSH, Darren, one item I have never been able to grasp from tuners that do utilize data logging such as a Shock Clock and a Dyno, why is it that when data logs record events, the events reach values easily well above the dynos capability, how can the information be compared or valid?

    I ask, using your posted information, based on peak recorded compression events of over 2ms or approximately 80 inches per second, yet your dyno run sheet maxes out at 10 IPS illustrated with what appears to be a possible 22 IPS not selected. Granted these may not be related dampers or runs.

    Just curious how the difference between data logged at high IPS values can be compared to testing / building dampers at low IPS values.

    I am likely wrong but was taught that to properly evaluate and utilize the equipment, the dyno needed to have a capability to match the recorded events of the Shock Clock. Dyno testing at low IPS works well for smooth terrain, like pavement, but even Roehrig recommends seriously high IPS for off-road applications.

    Not bashing your equipment or what results you achieve, just curious how other shops and your shop validate or tune true HSC events on the dyno.
    You are correct in the fact that the data I provided is from two different items. The data logging from a Lyrik fork, and the dyno info from a CRF250 Showa rear shock. As I mentioned, we spend a lot of money on this stuff...don't want to give up the recipe for free!

    As for your comments regarding equipment, I do disagree with your velocity ranges as our Roehrig crank dyno is capable of 1m/sec. A lot of damper tuning is done under that range. what you're referring to are "peak events" and that most of the average peaks fall near this range of the crank dyno. Again, not wanting to give out too much velocity info.

    That being said, we did ante up and purchase a Roehrig Engineering EMA dyno. This machine allows us the opportunity to create multiple wave forms and simulate actual bumps imported directly from our on-board data logging. This was a massive investment to further our research so that we could start to better understand the upper limitations of our piston and valve designs. We're looking into filming a serious of technical videos for the web and one of the things we're going to touch on is this subject. This will help put all of this into perspective.

    We take our engineering quite serious. PMK, with our engineering resources and our state-of-the-art CNC machining facility, and our technical services department, I can assure you that it would be like a day at Disneyland for someone like you if you were to come visit! You're welcome anytime...and that goes out to anyone!

    Darren

  21. #21
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    Thanks for the suggestions, mullen. I don't think I ever come close to bottoming my fork during normal riding, even though I can easily bottom it by bouncing the bike on purpose. I guess that's just my riding style to not ram into things. So with that said, it would seem like I don't need a whole lot of high speed compression. One lower bound that I can think of for the high speed compression damping is that it has to at least damp the unsprung weight of the wheel and fork lowers. That calculates out to [something I will figure out later].

    I'm not sure what I will gain from the datalogging. How will it tell me where more or less damping is needed? Do I get to do a Rouelle histogram analysis? (This reminds me that there is a lot of research done on this in the FSAE and professional motorsports community)

    Also, you are right that the adjuster knob on the ABS+ dampers affects damping way out to high speeds. Must be that speed shim. That being the case, one good suggestion I ran across was from some link to an article in Decline magazine that showed up in the ABS+ tunign thread. It goes something like:

    ride around and adjust the damper for best cornering and braking response. Note the damping force at 30cm/s according to the chart. (No dyno needed)

    Ride a bumpy section and adjust the damper for best performance / comfort. Note the value at 120cm/s.

    Find a shimstack that give you this curve without using the adjuster.

    Manitou ABS+ Tune kit Decline March 2012

    I have both a dynometer and a data-logger, but there isn't much point if they can't give me actionable recommendations.

  22. #22
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    Also, my ghetto hand dyno built out of unistrut and aluminum scraps can do 50 ips and arbitrary waveforms too.

    Last edited by beanbag; 11-02-2012 at 07:52 AM.

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    I'm not sure what I will gain from the datalogging. How will it tell me where more or less damping is needed? Do I get to do a Rouelle histogram analysis? (This reminds me that there is a lot of research done on this in the FSAE and professional motorsports community)
    Just looking at one common example....the question of "my suspension feels too stiff". This could because you're not getting enough travel for a given bump, or because you're using too much travel and excessively preloading the springs. The data would obviously tell you this. You ould then make adjustments, and create a histogram to evaluate the changes in combination with your notes on ride "feel".

    Also, you are right that the adjuster knob on the ABS+ dampers affects damping way out to high speeds. Must be that speed shim. That being the case, one good suggestion I ran across was from some link to an article in Decline magazine that showed up in the ABS+ tunign thread. It goes something like:

    ride around and adjust the damper for best cornering and braking response. Note the damping force at 30cm/s according to the chart. (No dyno needed)

    Ride a bumpy section and adjust the damper for best performance / comfort. Note the value at 120cm/s.
    Agreed, if you're using the external adjustments to control the peak events, than you're most likely making large compromises to the overall ride quality.

    I have both a dynometer and a data-logger, but there isn't much point if they can't give me actionable recommendations.
    I'm confused, because if you have this equipment you must already know what velocities fall under low speed and what events fall under high speed and can tune accordingly. Your original post is asking "Can somebody explain high speed damping? (on forks)"

    Also, my ghetto hand dyno built out of unistrut and aluminum scraps can do 50 ips and arbitrary waveforms too
    Pretty trick! It appears that you have to pull the arm to actuate the fork? How come you didn't go with a setup that would allow you to push(no pun intended) on it to make it easier on your back?

    Darren

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    I really like you homemade dyno. Its pretty slick. On the other hand, I am somewhat confused as to why you need a dyno for a fork with the TK damper

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    Ok, so which company is going to build me a digital fork that after a ride I can connect to my laptop and get a readout and retune the specs... All for under $500....


  26. #26
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    Quote Originally Posted by PUSHIND View Post
    You are correct in the fact that the data I provided is from two different items. The data logging from a Lyrik fork, and the dyno info from a CRF250 Showa rear shock. As I mentioned, we spend a lot of money on this stuff...don't want to give up the recipe for free!

    As for your comments regarding equipment, I do disagree with your velocity ranges as our Roehrig crank dyno is capable of 1m/sec. A lot of damper tuning is done under that range. what you're referring to are "peak events" and that most of the average peaks fall near this range of the crank dyno. Again, not wanting to give out too much velocity info.

    That being said, we did ante up and purchase a Roehrig Engineering EMA dyno. This machine allows us the opportunity to create multiple wave forms and simulate actual bumps imported directly from our on-board data logging. This was a massive investment to further our research so that we could start to better understand the upper limitations of our piston and valve designs. We're looking into filming a serious of technical videos for the web and one of the things we're going to touch on is this subject. This will help put all of this into perspective.

    We take our engineering quite serious. PMK, with our engineering resources and our state-of-the-art CNC machining facility, and our technical services department, I can assure you that it would be like a day at Disneyland for someone like you if you were to come visit! You're welcome anytime...and that goes out to anyone!

    Darren
    Good answer. The best way to evaluate HSC events is to buy a bigger dyno. The adapter / rate changer method is something I have heard of others fabricating. Basically trying to emulate higher IPS at the peak HP output of the dyno power supply.

    You will enjoy that EMA dyno and no doubt expand your capabilities.

    It has been about 10 years since I shopped for a dyno. This was the era when the shock clock and EMA units seemed to be just arriving. It was pretty cool to realize that with enough money you could data log, then go pretty much right into the dyno with the exact data logged run.

    PK
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  27. #27
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    Quote Originally Posted by PUSHIND View Post
    Just looking at one common example....the question of "my suspension feels too stiff". This could because you're not getting enough travel for a given bump, or because you're using too much travel and excessively preloading the springs. The data would obviously tell you this. You ould then make adjustments, and create a histogram to evaluate the changes in combination with your notes on ride "feel".
    I've never heard of using "too much travel". What would it look like in the data? If I combine the velocity and position data with the dyno data to get a plot of forces, I can only find justifications for reducing the compression damping at certain point. Where can I find rationale for adding more damping?

    I'm confused, because if you have this equipment you must already know what velocities fall under low speed and what events fall under high speed and can tune accordingly. Your original post is asking "Can somebody explain high speed damping? (on forks)"
    I only used the data logger setup on the car and not the bike yet. It was mainly used to find some peak velocities and confirm what are the shaft speeds for body rolling motions. On the Bilstein shocks I worked on, there was a clear transition between the bleed and shim portion. Other than that, I did not figure out from the data where to add more or less damping. I ended up tuning by feel and a few mathematical rules related to critical damping.

    How come you didn't go with a setup that would allow you to push(no pun intended) on it to make it easier on your back?
    Because usually rebound damping forces are higher, and that is achieved by pushing on the lever. But I mainly had it this way coz it lets stuff stick up above the shock.
    Last edited by beanbag; 11-02-2012 at 04:57 PM.

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    Too much travel would manifest itself at some point as excessive brake dive and/or bottoming out.

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    It has been about 10 years since I shopped for a dyno. This was the era when the shock clock and EMA units seemed to be just arriving. It was pretty cool to realize that with enough money you could data log, then go pretty much right into the dyno with the exact data logged run.
    Yeah, we're over six figures deep with our new setup which is pretty scary!

    I've never heard of using "too much travel". What would it look like in the data? If I combine the velocity and position data with the dyno data to get a plot of forces, I can only find justifications for reducing the compression damping at certain point. Where can I find rationale for adding more damping?
    I was speaking in reference to a specific situation.

    Rider A 175lbs running 75psi of air pressure in a 140mm fork is complaining of harshness in their suspension. Data logging shows that for a specific section of trail we expect to see an average travel being used of 45mm with that application. In fact this rider is only seeing 21mm of average travel even though their spring rate is correct. In this scenario the compression damping is too great, or curve too steep, to allow the wheel to get effective "through travel".

    Rider B 175lbs running 75psi of air pressure in a 140mm fork is complaining of harshness in their suspension. Data logging shows that for a specific section of trail we expect to see an average travel being used of 45mm with that application. In fact this rider is only seeing 70mm of average travel even though their spring rate is correct. In this scenario the compression damping is too soft, or curve to shallow, allowing the wheel to move too easily through the travel allowing sharp accelerations and building up more spring load causing excess firmness.

    Darren

  30. #30
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    Quote Originally Posted by PUSHIND View Post
    Yeah, we're over six figures deep with our new setup which is pretty scary!
    Darren

    @ Darren...Understand 100%, that was my turning point in suspension. Take it to the next level, or enjoy my aerospace career with good pay, benefits and less headaches. With no regrets, I prefer high end aerospace over suspension.

    Did you buy a new EMA from Roehrig or purchase the used one I saw listed on the internet that was low time and about a year or slightly more old?

    I'm assuming you purchased a sister unit to the one JGR has. In my opinion that is the capability required, I just am not sure the bicycle components structurally can handle those repeated tests / loads without silly failures. Anything with snaprings or plastic based sealheads would be in question.



    @Beanbag / OP, sorry for the derail. The others have posted good info to guide you. To keep it simple, in regards to HSR, this shim setting requires the ability to take a deep stroke extension and control but also smoothly blend the high compressed spring force into a low spring force.

    Getting more technical...So basically, this works the firmer portion of the shims (but in reality all shims and freebleed port) to control extension speed while tapering onto the less firm portion of the shims and ultimately only the freebleed (not 100% freebleed but close). In riding, you expect rebound extension to not hold the wheel packed or compressed nor allow it to bounce. Sadly, most bicycle riders overlook that proper rebound is also a respectable aid in how a bike turns and holds a line through a corner. A fast rebound will make the bike run wide in corners, while a slow rebound can contribute to "tuck" or with soft terrain knifing. Ultimately, this also directly relates to the forks geometric trail dimension, dynamic trail dimension, dynamic headtube angle, and fork offset.

    As for your HSC true question. The compression control can become more complex than the rebound. Here's why. Compression is not controlled by a finite force of the spring. Compression forces are dependent upon many factors. Some would be obvious rider weight, style and terrain. More complex though are headtube angle, sag, fork tube overlap, stiction, spring drag / air seal drag, damper shaft to cartridge body ratio, valve body area, valve body to shim fulcrum distance, piston edge effect and then the more typical and easy stuff such as shim stack formats, oil viscosity.

    In a nut shell, the goal of HSC, is to provide a somewhat platform situation but not really getting the job done. The forks freebleed will allow the fork to dive or wallow if open excessively. So in many senses, the freebleed (LSC adjuster) often is more of a pressure limiting orifice to control cartridge peak pressure in an open style cartridge system. In a closed cartridge system, the function is similar, however the control is not against the open chamber but against the cartridges pressure function IFP, bladder etc.

    LSC must be set so the shims and freebleed find that equilibrium of no wallow or dive, and yet be able to assist in tuning cartridge pressure dumping. Ideally, another circuit known as a midvalve will be employed. The typical LSC is by static shimming, while a midvalve is a dynamic shim set on the opposite side of the piston from the rebound shims. The MV is able to pick up the deficiency of the LSC shims, and offer the proper mid travel support, thereby controlling dive and getting better transitions into the deep portion of travel. Sad part about a midvalve is that often the cartridge shaft to cartridge bore ratio is poor, can not be tuned, and forces compromises on MV settings. Also, in many situations, the optimum MV settings are not ones that provide long MV shim life.

    HSC, is a form where in rapid suspension compression, while all circuits combined give total HSC values, in theory, the LSC, and MV phase out, leaving only the firmer portion of the static shims (actually all static shims combined) and the ability of the freebleed to control but dump cartridge pressure. This rapid movement creates rapid fluid flows which can be felt as spikes. They can occur at both high and low vehicle speeds. The typical term used when testing for HSC settings is a square edged bump (root).

    The earlier items mentioned, especially fork overlap and geometry play big on this as mechanical binding is very commonly confused for HSC.

    Tuning HSC ca provide a challenge. I agree with Darrens approach of the dyno in HSC testing, provided the numbers are real world. Unfortunately, the dyno is truly linear in motion and most times will not see mechanical issues. Therefore, when setting HSC, it is best to test sections of terrain that have the fork well compressed, typically about 50%. This lessens the forks length / leverage and binding. Under these conditions, normally it under braking into chop / hack. You need to focus on if the hands feel true spikes or smooth increase from added spring compression. Then make a change, easiest is opening the LSC, and note how it feels in the same conditions ( yes it may bob more during approach), but is there less harshness? Try adding compression until harshness is felt. This will offer insight into how to alter the static shim stack. Often the easiest change is an adjustment to the clamping shim diameter. Other shims may require changes also, but the clamp is a good start.

    As for how these conditions plot on a dyno, all transition should be smooth. In regards to the slope for HSC, you are dealing with preferences of each individual rider, so this will vary the requirements seen by the dyno, and the degree of slope plotted. In a nutshell, no two riders are the same, so in theory, each riders ideal setting will be different when plotted by a dyno. The dyno can ensure that multiple sets of suspension perform similar for a given rider. The dyno can help pinpoint mechanical concerns such as port area concerns, shaft / body ratio issues, or large errors in shim selection. In the end, the best dyno setting still require someone to ride them.

    Not sure if this helped or just rambled.

    PK
    Last edited by PMK; 11-03-2012 at 05:34 AM.
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    Data loggers and dyno's are great but the high speed recording modes on some of the newer cameras are also a great tool, particularly for evaluating tyre + suspension performance. Being able to step through some 240fps footage allows you to quickly determine which of the two compression issues Darren was talking about. Corner entry and exit footage can also allow you to see what you're rebound is doing. For shorter suspension travel in the 100-120mm range, the suspension effect of large volume tyres plays a big part in the overall package, to the tune of adding 20-40mm of extra "travel". The camera helps see how the tyre and suspension interact.

    I've got a small Canon that has frame by frame playback in the camera so all of this can be done with a couple of people trailside.

    Grab a mate, grab a camera and get some footage.

  32. #32
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    Quote Originally Posted by TigWorld View Post
    Data loggers and dyno's are great but the high speed recording modes on some of the newer cameras are also a great tool, particularly for evaluating tyre + suspension performance. Being able to step through some 240fps footage allows you to quickly determine which of the two compression issues Darren was talking about. Corner entry and exit footage can also allow you to see what you're rebound is doing. For shorter suspension travel in the 100-120mm range, the suspension effect of large volume tyres plays a big part in the overall package, to the tune of adding 20-40mm of extra "travel". The camera helps see how the tyre and suspension interact.

    I've got a small Canon that has frame by frame playback in the camera so all of this can be done with a couple of people trailside.

    Grab a mate, grab a camera and get some footage.
    100% correct, riders can't lie when video proof is there.

    FWIW, It is a known fact that when I test with riders and accomplish best settings for an individual, whether moto or MTB, I listen intently on what is said from the riders perspective, see how their comments compare to what I watched. If the rider makes his own suggestions on what clicker to "click", I will agree, and make my own adjustments. Send them back out and again get their feedback and compare to what I watched. A good majority of the time, what the rider feels is valid but the change in settings wanted is incorrect.

    The obvious question from me upon their return from a short hot lap "is it better?". Most riders are setback slightly to realize when I explain the exact change and why I made the change, that their choice would be a move in the wrong direction.

    Most common complaint is in regards to a forks HSC, especially under braking with hack. Many times this is resolved with a rear shock setting change, crazy but true where we ride. The rear may not track properly or could be pitching around the front axle. Settle the rear, the rider is more confident and riding relaxed, which settles the chassis further, allowing suspension to work, resolving the apparent HSC issue. Crazy but often happens. As an added benefit, corner speed is also increased.

    Again, the camera does not lie.

    PK
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    Ok, so which company is going to build me a digital fork that after a ride I can connect to my laptop and get a readout and retune the specs... All for under $500....
    I wish! We's sell a ton of those!

    Did you buy a new EMA from Roehrig or purchase the used one I saw listed on the internet that was low time and about a year or slightly more old?

    I'm assuming you purchased a sister unit to the one JGR has. In my opinion that is the capability required, I just am not sure the bicycle components structurally can handle those repeated tests / loads without silly failures. Anything with snaprings or plastic based sealheads would be in question.
    The dyno on the web that you're refering to is owned by ling time buddy of mine Dave Weagle. Initially, we were going to buy that one and trade our crank dyno to him as part of the deal. Long story short, we chose to keep the crank dyno for our technical services department to use and have the EMA for engineering. Dave's unit is very well configured, but because of our dual use for both MTB and Moto, we ultimately went direct and had Roehrig build us a custom unit configured for our specific needs.

    Data loggers and dyno's are great but the high speed recording modes on some of the newer cameras are also a great tool, particularly for evaluating tyre + suspension performance. Being able to step through some 240fps footage allows you to quickly determine which of the two compression issues Darren was talking about. Corner entry and exit footage can also allow you to see what you're rebound is doing. For shorter suspension travel in the 100-120mm range, the suspension effect of large volume tyres plays a big part in the overall package, to the tune of adding 20-40mm of extra "travel". The camera helps see how the tyre and suspension interact.

    I've got a small Canon that has frame by frame playback in the camera so all of this can be done with a couple of people trailside.
    Yeah, we have hundreds of hours of HS camera footage that we use in conjunction with all of our other toys. It does act as a very useful track/trailside tool. Again, when used in conjunction with other items, you can get a pretty good look at what's going on. Our youtube channel is pretty lame at this point, but here's a clip that's been up there for a while. We shoot between 420-1000f/s depending on the application.

    <iframe width="560" height="315" src="http://www.youtube.com/embed/odGDEa4TeJY?list=UUprHyRc4tmkQ918Bjx01ksA&amp;hl=e n_US" frameborder="0" allowfullscreen></iframe>

  34. #34
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    Quote Originally Posted by PMK View Post
    Related to the graphs posted by PUSH, Darren, one item I have never been able to grasp from tuners that do utilize data logging such as a Shock Clock and a Dyno, why is it that when data logs record events, the events reach values easily well above the dynos capability, how can the information be compared or valid?

    I ask, using your posted information, based on peak recorded compression events of over 2ms or approximately 80 inches per second, yet your dyno run sheet maxes out at 10 IPS illustrated with what appears to be a possible 22 IPS not selected. Granted these may not be related dampers or runs.

    Just curious how the difference between data logged at high IPS values can be compared to testing / building dampers at low IPS values.

    I am likely wrong but was taught that to properly evaluate and utilize the equipment, the dyno needed to have a capability to match the recorded events of the Shock Clock. Dyno testing at low IPS works well for smooth terrain, like pavement, but even Roehrig recommends seriously high IPS for off-road applications.

    Not bashing your equipment or what results you achieve, just curious how other shops and your shop validate or tune true HSC events on the dyno.

    PK
    Having that kind of dyno capability is more important for anyone creating new valve geometry than someone simply retuning an existing damper, because when working with an existing piston, one has to simply deal with its flow capacity characteristic on the assumption that it is capable of allowing enough oil flow at the peak velocities. The reason for this is that the vast majority of critical motions (with respect to both stability and harshness) occur at only a fraction of the highest peak velocities (have personally logged velocities substantially higher than shown in those graphs, and the ShockClock has a very low sample rate as it is). I certainly don't want to speak for other tuners, but building new pistons for existing dampers (if they are well developed dampers with no known tendency to spike at peak velocities) allows one the luxury of simply matching or exceeding the HS port area of the stock piston in order to assume that the velocity ceiling of the new valve is at least as high as the old one.

    How this is relevant: The geometry of shimmed valves typically lends itself to surprisingly linear high speed F-V curves up until the actual port geometry becomes the limiting factor in terms of flow (quite low in rebound, very high in compression), because the distances shims actually bend are surprisingly tiny within their linear range of motion (for example, shim displacement at its OD may be as little as 0.1mm at 0.5m/s in certain dampers). Most progression or digression, for example, is little to do with the specific port geometry and largely to do with the transition characteristics between the LS and the HS circuits.

    A capable engineer can get a good estimation of the choking velocities of the HS porting just through calibrated measurements alone, which allows for some degree of extrapolation of the HSC curve - a curve that is linear from 0.1m/s to 1m/s is not going to suddenly and violently change by 1.1m/s, for example, but may have a distinct change in its gradient by 2m/s. The bigger the ports and the stiffer the valving, the further the extrapolations are valid, though these need to be calibrated through both calculation and measurement. This extrapolation can be a somewhat imprecise science, but it can be implicitly confirmed by further datalogging with known port geometry, and is something that is observable and measurable with certain high end shocks that are already on the market (particularly in rebound), even well under the 1m/s limit of the Roehrig crank dyno that we have.

    However, it should be noted that the majority (not the entirety, but the majority) of good tuning doesn't come from the super complex mathematical analyses, but from fundamental measurements such as comparative travel usage, statistical analysis of position and velocity measurements, derived accelerations etc. The ShockClock, despite its many limitations as a datalogger, gives a pretty good idea of a lot of that stuff.
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    Having that kind of dyno capability is more important for anyone creating new valve geometry than someone simply retuning an existing damper, because when working with an existing piston, one has to simply deal with its flow capacity characteristic on the assumption that it is capable of allowing enough oil flow at the peak velocities. The reason for this is that the vast majority of critical motions (with respect to both stability and harshness) occur at only a fraction of the highest peak velocities (have personally logged velocities substantially higher than shown in those graphs, and the ShockClock has a very low sample rate as it is). I certainly don't want to speak for other tuners, but building new pistons for existing dampers (if they are well developed dampers with no known tendency to spike at peak velocities) allows one the luxury of simply matching or exceeding the HS port area of the stock piston in order to assume that the velocity ceiling of the new valve is at least as high as the old one.

    How this is relevant: The geometry of shimmed valves typically lends itself to surprisingly linear high speed F-V curves up until the actual port geometry becomes the limiting factor in terms of flow (quite low in rebound, very high in compression), because the distances shims actually bend are surprisingly tiny within their linear range of motion (for example, shim displacement at its OD may be as little as 0.1mm at 0.5m/s in certain dampers). Most progression or digression, for example, is little to do with the specific port geometry and largely to do with the transition characteristics between the LS and the HS circuits.

    A capable engineer can get a good estimation of the choking velocities of the HS porting just through calibrated measurements alone, which allows for some degree of extrapolation of the HSC curve - a curve that is linear from 0.1m/s to 1m/s is not going to suddenly and violently change by 1.1m/s, for example, but may have a distinct change in its gradient by 2m/s. The bigger the ports and the stiffer the valving, the further the extrapolations are valid, though these need to be calibrated through both calculation and measurement. This extrapolation can be a somewhat imprecise science, but it can be implicitly confirmed by further datalogging with known port geometry, and is something that is observable and measurable with certain high end shocks that are already on the market (particularly in rebound), even well under the 1m/s limit of the Roehrig crank dyno that we have.

    However, it should be noted that the majority (not the entirety, but the majority) of good tuning doesn't come from the super complex mathematical analyses, but from fundamental measurements such as comparative travel usage, statistical analysis of position and velocity measurements, derived accelerations etc. The ShockClock, despite its many limitations as a datalogger, gives a pretty good idea of a lot of that stuff.
    Steve, are you the Steve originally from Oz? Anyway, I checked out your site....looks like you've got some cool stuff going on.

    Darren

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    Quote Originally Posted by PUSHIND View Post
    Steve, are you the Steve originally from Oz? Anyway, I checked out your site....looks like you've got some cool stuff going on.

    Darren
    I am indeed, thank you, and likewise. How did you know I am from Australia?

    Steve
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    I am indeed, thank you, and likewise. How did you know I am from Australia?
    Because I know all things suspension tuning! LOL

    Actually you came up in a conversation recently with a colleague and I seemed to remember having some email conversations with you via rotorburn or something trying to coordinate maybe a test sample or something. Anyway, just putting two and two together, but still had to ask to confirm.

    Darren

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    Steve, I read your post quickly. I don't disagree. I would add though that sometimes on poorly designed pistons or valve bodies, sometimes changes can be easily made to see large gains.

    As an example, White Power forks used on KTMs have had valve body design concerns. DIY / home tuners have followed advice of others and made simple changes obtaining excellent results with simple tools such as a Dremel to "port" the valve body. This is a good example of F-V concerns from the oem.

    One concept often overlooked, is flow based on damper shaft to body bore ratio. From experience, each ratio tends to lend itself to different port area percentage values. Add to this edge effect, port shape, and fulcrum distance the net design is sometimes not an easy target.

    Obviously there must be a need to replace or modify the valve body. Sometimes you can have too much flow capability.

    PK
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    Quote Originally Posted by PUSHIND View Post

    Rider B 175lbs running 75psi of air pressure in a 140mm fork is complaining of harshness in their suspension. Data logging shows that for a specific section of trail we expect to see an average travel being used of 45mm with that application. In fact this rider is only seeing 70mm of average travel even though their spring rate is correct. In this scenario the compression damping is too soft, or curve to shallow, allowing the wheel to move too easily through the travel allowing sharp accelerations and building up more spring load causing excess firmness.

    Darren
    Please explain this scenario some more. How did you know that a section of trail is "supposed" to only use 45mm of travel? How can 70mm of travel be too much? Don't you want to use as much travel as possible to best follow the terrain?

  40. #40
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    Quote Originally Posted by PUSHIND View Post
    Because I know all things suspension tuning! LOL

    Actually you came up in a conversation recently with a colleague and I seemed to remember having some email conversations with you via rotorburn or something trying to coordinate maybe a test sample or something. Anyway, just putting two and two together, but still had to ask to confirm.

    Darren
    Oh right, that was a while ago! If you're ever up in Whistler, give me a yell, would be nice to put a face to the name

    Quote Originally Posted by PMK View Post
    Steve, I read your post quickly. I don't disagree. I would add though that sometimes on poorly designed pistons or valve bodies, sometimes changes can be easily made to see large gains.

    As an example, White Power forks used on KTMs have had valve body design concerns. DIY / home tuners have followed advice of others and made simple changes obtaining excellent results with simple tools such as a Dremel to "port" the valve body. This is a good example of F-V concerns from the oem.

    One concept often overlooked, is flow based on damper shaft to body bore ratio. From experience, each ratio tends to lend itself to different port area percentage values. Add to this edge effect, port shape, and fulcrum distance the net design is sometimes not an easy target.

    Obviously there must be a need to replace or modify the valve body. Sometimes you can have too much flow capability.

    PK
    Agreed - some moto dampers use HS throttling ports within the pistons, where the smallest cross section is not the same as the port area sealed by the shim stacks. These are intended to provide a severe ramp up (spike/hydraulic lock, essentially) in damping at SUPER high speeds (like when you overshoot a 100ft stepdown to flat) where the HS valving has been completely overwhelmed by the momentum of the huge rigid sprung mass of the motorbike - which is far less of a concern with bicycles simply because the rider's mass (and strength) is almost always the limiting factor.

    However, if those throttling ports are too small (changes in damping force are proportional to the fourth power of the port diameter!) then that spiking will occur too severely at too low a speed. If the ports are much too large, it can be difficult to create a sufficiently stiff valving stack, flow through the LS circuit (such as the rebound adjuster) can be reduced to the point where the adjuster's effectiveness suffers severely, and other factors such as machining precision and shim tolerances become much more critical, which in turn means less precise damping control - particularly in the crucial transition region between HS and LS damping.

    Any valve design, as you say, needs to consider the mass flow rate per unit shaft speed, which is determined by the bore and shaft sizes.

    Quote Originally Posted by beanbag View Post
    Please explain this scenario some more. How did you know that a section of trail is "supposed" to only use 45mm of travel? How can 70mm of travel be too much? Don't you want to use as much travel as possible to best follow the terrain?
    Not necessarily, there are conflicting requirements on travel use:
    1. More travel use from ground-based inputs typically means less harshness and better wheel tracking. Obviously, this is good.
    2. More travel use from rider-based inputs typically means less stability, slower response and settle times, more energy dissipation (less liveliness) and in some cases (from either ground-based or rider-based inputs), higher peak forces (either from higher spring forces or bottom out). These are usually considered bad. As a result, the ideal suspension setup is one that minimises the negatives, and maximises the positives, you will never completely eliminate one issue or the other - though you may reduce negative factors into insignificance.
    Last edited by Steve VS; 11-05-2012 at 03:26 AM.
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    Just a couple questions for now:
    What does it mean when the fork has kind of a springy, rubbery feel? Where is the damping lacking?
    Is there always a trade-off between platform / brake dive resistance and some kind of small bump harshness? When I turn the compression knob back and forth, the fork seems to alternate between these conditions.

    Sometimes, I think things are exactly right. For example, when I hit a root at medium speed, the front wheel makes a "plop" sound as if the tire is flat, and there isn't much shock to the handlebars.

    Other times, even hitting a 2" rock will cause the fork to bounce off.

    Other times I hit the trailing edge of a small pothole and it is more harsh than I expect.

    For now, I took one main shim out of my ABS+ stack, which basically means the HSC is a bit lower slope and intercept.

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    Oh one other thing, regarding mullen's comment that there is a lot of "crossover" on these ABS+ dampers. I think that just means that the adjustable orifice is really big and even flows at high speeds. Contrast this with the valving design on Bilstein shocks. The bleed port is actually the first shim against the piston, but with some notches cut into it. Once you exceed a certain pressure, this shim lifts up along with all the other ones. I'm not sure if it is this aspect of the design, but it really lets the linear portion of the shims take over right after the digressive knee. On these ABS+ dampers, instead you have this big progressive / parabolic damping curve all the way up to high speeds. One thing I also learned from car suspension is that if you still have a parabolic curve into the mid-speed regions, it will feel like ass.

    Oh yeah, that's another thing that bugs me. Why do people with these high dollar dynos only plot a few points along the x axis? It totally hides the low speed behavior and crossover transition. (IMHO more important than whether your piston ports are limiting your flow at super high speeds) Wouldn't you appreciate this level of detail? For example:
    Last edited by beanbag; 11-05-2012 at 03:50 AM.

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    Quote Originally Posted by Steve VS View Post
    Oh right, that was a while ago! If you're ever up in Whistler, give me a yell, would be nice to put a face to the name



    Agreed - some moto dampers use HS throttling ports within the pistons, where the smallest cross section is not the same as the port area sealed by the shim stacks. These are intended to provide a severe ramp up (spike/hydraulic lock, essentially) in damping at SUPER high speeds (like when you overshoot a 100ft stepdown to flat) where the HS valving has been completely overwhelmed by the momentum of the huge rigid sprung mass of the motorbike - which is far less of a concern with bicycles simply because the rider's mass (and strength) is almost always the limiting factor.

    However, if those throttling ports are too small (changes in damping force are proportional to the fourth power of the port diameter!) then that spiking will occur too severely at too low a speed. If the ports are much too large, it can be difficult to create a sufficiently stiff valving stack, flow through the LS circuit (such as the rebound adjuster) can be reduced to the point where the adjuster's effectiveness suffers severely, and other factors such as machining precision and shim tolerances become much more critical, which in turn means less precise damping control - particularly in the crucial transition region between HS and LS damping.

    Any valve design, as you say, needs to consider the mass flow rate per unit shaft speed, which is determined by the bore and shaft sizes.



    Not necessarily, there are conflicting requirements on travel use:
    1. More travel use from ground-based inputs typically means less harshness and better wheel tracking. Obviously, this is good.
    2. More travel use from rider-based inputs typically means less stability, slower response and settle times, more energy dissipation (less liveliness) and in some cases, higher peak forces (either from higher spring forces or bottom out). These are usually considered bad. As a result, the ideal suspension setup is one that minimises the negatives of both, and maximises the positives, but you will never completely eliminate one or the other (though you may reduce negative factors into insignificance).

    In bold, a concept that is very often misunderstood, overlooked in design, and why many aftermarket suspension valves fail to provide anything better than a wallowy ride.

    Adding to this, the as you call them throttling ports, for those unfamiliar with them, are not the actual orifice port. The stepped throttling port has a larger net area, which more easily applies pressure onto the shim face to unseat it. In addition, the ports sealing surface, is also the derived fulcrum dimension, and when too large can make tuning via the clamp size difficult. This as mentioned, correlates to how the transition is felt by the rider as the HSC is utilized.

    Beanbag, not answering for Darren, but in laymans terms, as I read what he posted, it sounds like typical mid stroke harshness / midstroke rampup, riding low in the stroke since his example is a damping based not spring based concern. The situation can also be an overdamped setup that may have the rider opting for a softer airspring pressure on account of harshness from the shims / valving or in some cases too much bath oil causing a poor compression ratio or even a poor selection of hydraulic bottoming control. This is when it becomes very important to find the specific area creating the ride quality problem. As for the knowing it should be 45mm, that is experience and / or previous logs of what was working on another machine.

    For others reading and wondering how to resolve a HSC concern without all the data logging and dynos, build yourself a square edge style bump, or find one on the trail, that is approximately 50% of rated suspension stroke. Ensure it is secure and will not move, plus ideally is somewhat rounded on the edges. Running a high tire pressure so as to save your rim and get accurate feedback, use this as your tuning test bed that you can evaluate changes with. It is best to not pedal across it, enter exactly straight and not too fast initially. As your damping dials in, speeds with minimal feedback will increase. If your fork has a HSC adjuster, it's pretty easy to find a "best" setting for how the fork has been built within a few minutes. FWIW, on a fork like our Fox 40 on the Ventana tandem, we adjust settings while riding. The froks HSC is on top by the bars and the rear is dialed in via the old style DHX5.0 air Propedal knob. Typically we ride in certain range of the adjuster and make a click one side or the other to optimize for the terrain that day. The bike and suspension is talking to you. It's up to you to understand the language.

    Consider also, that when you send your stuff to big shops, like those posting here, you should still work the clickers to optimize the settings. There are many riders that are scared of screwing it up. Right down your initial clicker and pressure settings, then spin away on the adjusters.

    PK
    Reps! We don't need no stickin' reps!

  44. #44
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    Quote Originally Posted by PMK View Post
    The situation can also be an overdamped setup that may have the rider opting for a softer airspring pressure on account of harshness from the shims / valving

    build yourself a square edge style bump, or find one on the trail, that is approximately 50% of rated suspension stroke. Ensure it is secure and will not move, plus ideally is somewhat rounded on the edges. Running a high tire pressure so as to save your rim and get accurate feedback, use this as your tuning test bed that you can evaluate changes with. It is best to not pedal across it, enter exactly straight and not too fast initially. As your damping dials in, speeds with minimal feedback will increase.
    both good points for me to consider

  45. #45
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    Quote Originally Posted by PUSHIND View Post
    I wish! We's sell a ton of those!
    That would be fairly easy to do these days,especially if people are willing to hand over 500$ in retail, but I guess you already know that?



    Magura

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    Please explain this scenario some more. How did you know that a section of trail is "supposed" to only use 45mm of travel? How can 70mm of travel be too much? Don't you want to use as much travel as possible to best follow the terrain?
    Meaning that a group of test riders agree that using that much travel gives the best compromise of comfort and control.

    Oh right, that was a while ago! If you're ever up in Whistler, give me a yell, would be nice to put a face to the name
    For sure. Likewise if you're ever on Colorado you should plan on stopping by PUSH.

    Oh yeah, that's another thing that bugs me. Why do people with these high dollar dynos only plot a few points along the x axis? It totally hides the low speed behavior and crossover transition. (IMHO more important than whether your piston ports are limiting your flow at super high speeds) Wouldn't you appreciate this level of detail? For example:
    I'm actually capable of spitting out any data that you'd like. I was just showing a general graph to help visualize what I was talking about, not to actual provide exact data. You've obviously seen what dyno charts look like, but a lot of forum members have not.

    That would be fairly easy to do these days,especially if people are willing to hand over 500$ in retail, but I guess you already know that?
    Not with my current capabilities and resources! I guess we'll have to hire an electronics engineer!

    Darren
    Attached Thumbnails Attached Thumbnails Can somebody explain high speed damping? (on forks)-dyno-2.jpg  


  47. #47
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    Anyone know what dyno this is? These are the HSC numbers I want to know.

    <iframe width="420" height="315" src="http://www.youtube.com/embed/32XLPjdDlRA" frameborder="0" allowfullscreen></iframe>
    Bend, Oregon

  48. #48
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    Anyone know what dyno this is? These are the HSC numbers I want to know.
    That's the Roehrig EMA dyno, similar to the one we purchased recently.

    Darren

  49. #49
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    Quote Originally Posted by PUSHIND View Post
    That's the Roehrig EMA dyno, similar to the one we purchased recently.

    Darren
    DANG that would tell me some info! Googling away now.
    Bend, Oregon

  50. #50
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    I would need the 4k for the forces I need, and CRAP I don't even want to know the cost.
    Bend, Oregon

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