Shock Theory

[Beat95yj]

Agreed
But I wanted Dougal to explain us where he got his info from. Personal experience ? Offroad ?



Also agreed, but I'm curious to hear if anyone runs digressive valving in their shocks succesfully on an offroad application.
One of the first things to do with Bilstein as soon as you get them is to ditch their valving for a more "conventional" approach.
I'll also say that some/all Fox OEM shocks are valved digressive (raptor comes to mind).

Digressive valving works well for crawlers. Really keep weight shifts from occurring quickly also prevent packing up when you go bombing through the desert. I don’t know why people don’t do digressive rebound and linear compression on a desert shock. Seems like a no-brainer. Digressive compression has all kinds of issues for offering. Basically you blow through this stiff part and bottom out hard.

For years all Donahoe / Icon were digressive. Not sure anymore. For a time lots of lift kit companies sold digressive Monotubes, manufactured by Edelbrock. For example, Rubicon Express.

 

[Weasel]

One particular topic lightly discussed in the past is the preference for higher spring rate with little preload and less damping, versus lower spring rate with more preload to achieve the same ride height and more damping to control the travel. This can of worms would go well here.

It seems people try this but it's a bandaid and I don't think it's the correct path. It gets lumped into the same group because each system in not well understood but they are separate.

The spring's job is to store that energy. The shock's job is to remove the energy as heat.

As noted above a stiff or soft spring stores the same amount of energy, force into the system.

Another aspect to ride comfort that isn't discussed as often: tires. Traction is discussed, but only from the aspect of "does it hook up or not?". Tire stiffness and pressure directly affect suspension. Put a 10ply tire on a 3000lb truck and you'll immediately know why.

Tires are part of it but are unsprung, they really should be an added component similar to a bump stop would be. But you are correct that there is a spring and damper in a tires. Air (damper) and I suppose the construction is the spring.

My suspension nerding has been on MTBs, dirt bikes, street cars, and leaf spring wheelers. Each platform has unique enough characteristics that we definitely can't apply blanket statements to all vehicles.

Ya know that's not really true, well some what. I agree that there are no blanket statements and it's a red flag for me when folks state - you only want xyz for this rig. If you understand the fundamentals of the systems well enough one should be able to ball park any application. Now that's not me either. So continue the discussion.


What's the deal with the Bilstein Blackhawk Anti cavitation valve? Seems to work really well but I can't seem to find out much info on it or what it can be used in or on. It seems popular but maybe it's not?

Stepping back from the shock shims and general shock setup I've been more interested in the setup and layout of parts of the shocks, like bypass tubes, placement of restriction valves, revivors and placement, hoses sizes, fittings, etc. Seems like there is alot of those little details that pop up every now and then but overall don't get much discussion.

 

[Beat95yj]

The ACV is another deflective disc piston in the reservoir. In theory, it should work, the same in any other shock with the same piston rod diameter. The compression resistance comes through that piston and the shock behaves like a twintube. It does allow a great reduction in nitrogen pressure. The higher the compression damping in a top mount reservoir shock the more nitrogen you need to force the oil through the piston without cavitation. The second working piston provides that resistance without excessive nitrogen pressure.

It’s also similar to the fox do a speed adjuster. It just does not have the adjustable orifice through the middle. I’ve never tried to run a fox adjustable resi on the dyno to see if it can be used to prevent cavitation with lower nitrogen pressures. to see if it can be used to prevent cavitation with lower nitrogen pressures. I have the older fox low speed adjusters and have not put them on the Dyno cause I don’t wanna take them off. #Lazy.

 

[AgitatedPancake]

Hydraulic sway bar devices have always been super intriguing to me. Even something like traditional end links being hydraulic rams that are interconnected with valves/adjustable orofices. Fully sealed, they act just like rigid sway bar links. But then you can open the valve and adjust the orofice size/add symmetrical valving that could allow the chassis to roll with low speed events, but acts progressively stiffer as the speed of the inputs ramp up.

You guys do bring up good points about all of the other aspects that go into the performance of a suspension as well. I think they're definitely worth mentioning in the context of any given configuration, but we could go down a huge rabbit hole on a few of those topics, which may be best suited to their own discussions. But we can just roll with it and see what comes up!

Weasel I haven't seen anything on that Bilstein valve you referenced, I'll have to do a little hunting.

Sweet to hear your input as well Frank! Being linear or progressive on the compression valving seems to make sense as far as bottom out resistance goes,very interesting to hear your notes about how body roll reacts to digressive (rebound?) valving. Rebound doesn't get talked about nearly as much, so that is sweet.

I had to look up what the ACV is, it looks to be Bilstein's Anti Cavitation Valve? How are those decreasing cavitation overall, decreasing the pressure drop across the main piston by having it do less work, with the reservoir-mounted valving taking up some of the load?

 

[AgitatedPancake]

The Chevy ZR2 comes with some fancy multimatics that have all sorts of intricate things going on with spool valves:

DSSV Damping Technology





And they're going with electronic control on the latest. Pretty cool to see the dyno graphs for various different settings here, looks like an impressive unit

 

[Beat95yj]

Digressive valving doesn’t reduce the amount of body roll, it just significantly reduces the rate at which the vehicle rolls. If the turn is long enough you will hit the same roll angle. In a shorter turn the vehicle will feel more sporty and more controlled.

 

[Beat95yj]

The ACV prevents cavitation by slowing the rate that piston rod displaces oil into the reservoir and keeps pressure on the oil. That’s basically what nitrogen does.

 

[Weasel]

Digressive valving doesn’t reduce the amount of body roll, it just significantly reduces the rate at which the vehicle rolls. If the turn is long enough you will hit the same roll angle. In a shorter turn the vehicle will feel more sporty and more controlled.

Another good point. Shocks don't control sway they control the rate. Hear that a lot that people want to stiffen the shocks for body roll.

I'm hearing good thing on the Multimatic shocks but they don't seem build for racing per say. Just the overall construction seems light.

 

[bdkw1]

For years all Donahoe / Icon were digressive.

That's because they were designed for the mall crawler crowd. They work great on the street and ok in the dirt.

 

[bdkw1]

The Bilstien ACV's work well on front CO's. BP's work better with resi out the bottom. AGM changed all there Blackhawks to resi out the bottom with no ACV's. They do not have enough blow off for big hits and make the back kick. Could this be tuned out? Maybe with piston design changes but resi out the bottom is proven and easier to do.

 

[Dougal]

This goes against everything I've seen, succesfully implementefd, worked on and took apart from other tuners.

There's more innovation in MTB shocks than TTs. Rally cars are pretty high in the list of the crazy shit too.

Which bit are you unsure about? The rebound being firmer than compression or the low speed compression being higher damping ratio than high speed compression?

Don't confuse damping ratios with absolute force values. They're not the same thing.

MTB shocks are mostly copying each other. Most of the MTB suspension is really really bad.

Shocks work at all speeds, but suspensions are designed for a certain speed.

No they're not.

Agreed
But I wanted Dougal to explain us where he got his info from. Personal experience ? Offroad ?



Also agreed, but I'm curious to hear if anyone runs digressive valving in their shocks succesfully on an offroad application.
One of the first things to do with Bilstein as soon as you get them is to ditch their valving for a more "conventional" approach.
I'll also say that some/all Fox OEM shocks are valved digressive (raptor comes to mind).

I'm a suspension engineer with my own dyno.

You may be confusing damping rates with damper force.

 

[Dougal]

Digressive valving works well for crawlers. Really keep weight shifts from occurring quickly also prevent packing up when you go bombing through the desert. I don’t know why people don’t do digressive rebound and linear compression on a desert shock. Seems like a no-brainer. Digressive compression has all kinds of issues for offering. Basically you blow through this stiff part and bottom out hard.

For years all Donahoe / Icon were digressive. Not sure anymore. For a time lots of lift kit companies sold digressive Monotubes, manufactured by Edelbrock. For example, Rubicon Express.

Digressive rebound packs on corrugations and mean you can't get a good balance between chassis control and stability. Those are the main reasons it sucks.
That doesn't mean you won't find it hidden inside some stock shocks though. Usually to calm body sway.

 

[Dougal]

You guys are obviously over my head in this discussion, but still very interesting. My question is why can’t a shock handle “bump duty” as well. It doesn’t seem like it would be that hard to incorporate it, but I know of no shock that does. It would seem like it would make packaging and fabing easier.

In my “simple mind”, I would think they could make shocks also handle some “sway bar” duty. Like a hydraulic tube with a valve between left and right that could be adjusted to resist roll.



Yes, X2

Bump stop loads are far higher than damper loads. While it's no problem to design a hydraulic bottom-out into a shock (it's done in MTB and Moto) the vehicle shock mounting points often aren't strong enough. Only strut type applications take bottom-out forces through the same mounting points.

You'd also have to make the shock a lot stronger (buckling loads on the shaft etc).

 

[Bebop]

Which bit are you unsure about? The rebound being firmer than compression

That bit

I'm a suspension engineer with my own dyno.

Do you have long travel Offroad experience?

You may be confusing damping rates with damper force.

Could you clear it up for us ? Thanks :)

 

[Dougal]

That bit


Do you have long travel Offroad experience?


Could you clear it up for us ? Thanks :)

Sure, but this is a bit like explaining that the sky is blue. Because almost every suspension runs more rebound than compression. Only a few run them somewhat equal.
It's necessary because otherwise you're adding damping force to spring force on compression and not removing enough energy on rebound. The result is a shock that is harsh AF and also ridiculously bouncy.

Here's a dyno plot form a Dobinsons shock. Rebound is roughly twice compression which is pretty typical.

Here's a plot of a pair of shocks that were harsh and yet left the vehicle feeling uncontrolled. No idea what the original application was supposed to be as the part-numbers are 40 years old and records can't be found.
These have almost equal compression and rebound. Terrible ride, terrible handling, harsh and wallowing both onroad and off.

Damper rates are how much force they deliver for velocity. Damper forces are the result of the damper rate multiplied by the velocity.
Dampers can have very different rates at different speeds.

 

[AgitatedPancake]

Great back and forth guys. The shocks impact on the rate of body roll makes sense as well.

And thanks Dougal for your interesting insight as well.

It's necessary because otherwise you're adding damping force to spring force on compression and not removing enough energy on rebound. The result is a shock that is harsh AF and also ridiculously bouncy.

I find this particular comment pretty interesting. In long travel offroad, are we really trying to remove much energy in rebound? It seems like we're trying to reset the axle as fast as possible before the next compression event, but doing so in a somewhat controlled manner (maybe bypass rebound tubes, or a "top out zone" in the shock to slow it down before pulling the strap tight. Of course having too little rebound would negatively effect ride quality everywhere else so it's always a compromise.

I guess a strange thing about the really high speed stuff is how little rebound time they spend with the tire actually contacting the ground. Like that Bryce Menzies video I put on the first page, he's literally skipping from whoop to whoop, compression event to compression event in some of those shots, with no tire contact during rebound. I know that's an edge case, but still interesting to observe

 

[bdkw1]

Bump stop loads are far higher than damper loads. While it's no problem to design a hydraulic bottom-out into a shock (it's done in MTB and Moto) the vehicle shock mounting points often aren't strong enough. Only strut type applications take bottom-out forces through the same mounting points.

You'd also have to make the shock a lot stronger (buckling loads on the shaft etc).

Have you had a look at the new Bilstien Blackhawk UTV shocks? With the piston area of the internal bump, I'm unsure how effective they are. Especially with the shaft size. Seems like better than nothing but not as good as a separate bump type marketing ploy.

 

[WaterH]

Bump stop loads are far higher than damper loads. While it's no problem to design a hydraulic bottom-out into a shock (it's done in MTB and Moto) the vehicle shock mounting points often aren't strong enough. Only strut type applications take bottom-out forces through the same mounting points.

You'd also have to make the shock a lot stronger (buckling loads on the shaft etc).

I agree with both points, you need stronger mounts and shocks. I just don’t see how that’s a problem. On the axle, If 1/4” plate is not strong enough, use 3/8”. If that’s not strong enough, use 1/2”. On the frame, you may have to use a plate to spread out the force. Of course the shock company would build the shock to hold up. It just seems to me one mount on the axle and frame at each corner to handle spring, shock and bump is a nice clean way to do it. (Assuming coil overs)

On your discussion about rebound dampen, I’ve never understood the logic of increased damping on rebound. It seems to me that when you travel over washboard, you are eventually riding on the bump stops. I live on a dirt road and I think I’ve experienced this In my Bronco. The beginning of the washboard is not bad, but after 20 feet, I feel like I’m on the stops. I assume that you are correct because everything I read says the same, but I sure would love to have a completely adjustable shock (both compression and rebound) and do some testing. I know there are adjustable shocks , but I don’t want take them apart. I would like adjustment knobs or some such.

 

[AgitatedPancake]

Have you had a look at the new Bilstien Blackhawk UTV shocks? With the piston area of the internal bump, I'm unsure how effective they are. Especially with the shaft size. Seems like better than nothing but not as good as a separate bump type marketing ploy.

Ok those things are pretty rad. Watching this new video on them from Shock Therapy. Cool explanations and cutaway model

 

[Dougal]

Great back and forth guys. The shocks impact on the rate of body roll makes sense as well.

And thanks Dougal for your interesting insight as well.



I find this particular comment pretty interesting. In long travel offroad, are we really trying to remove much energy in rebound? It seems like we're trying to reset the axle as fast as possible before the next compression event, but doing so in a somewhat controlled manner (maybe bypass rebound tubes, or a "top out zone" in the shock to slow it down before pulling the strap tight. Of course having too little rebound would negatively effect ride quality everywhere else so it's always a compromise.

I guess a strange thing about the really high speed stuff is how little rebound time they spend with the tire actually contacting the ground. Like that Bryce Menzies video I put on the first page, he's literally skipping from whoop to whoop, compression event to compression event in some of those shots, with no tire contact during rebound. I know that's an edge case, but still interesting to observe

Basically the amount of damping force required to achieve a fast and stable rebound is way higher than most people appreciate.

Have you ever driven a vehicle with a blown shock or broken mount? They're completely uncontrollable in any dynamic situation. Even in a relatively stable situation of driving down a straight road the bounce and wallow is incredible.

Springs absorb and return bump energy. If you don't damp out that energy in the shock on compression and rebound you're in for a bad time. Uncontrolled rebound will have the inertia of the unsprung weight (wheels, hubs, axles, swingarm) destroying your shocks in short order. That's on top of the vehicle being unstable.

Have you had a look at the new Bilstien Blackhawk UTV shocks? With the piston area of the internal bump, I'm unsure how effective they are. Especially with the shaft size. Seems like better than nothing but not as good as a separate bump type marketing ploy.

No I haven't. I find it basically impossible to keep up with even mainstream suspension developments, let alone all the niche products.

The hydraulic bump stops I've dealt with (suspension and industrial applications) have a plunger running deeper past a set of orificies so they get more progressive. The deeper it goes the more it passes and the firmer it gets. When you're forcing oil through fixed size orifices the forces square with speed.
Hit the bottom-out circuits slowly and you likely won't even feel it. Hit them at 3 times the speed and you've got 9 times as much hydraulic force. 4 times the speed is 16x the force etc.

It doesn't often take a lot of hydraulic bump-stop force to suck the life from the end of the stroke and prevent the hard bottom-out shock.

I agree with both points, you need stronger mounts and shocks. I just don’t see how that’s a problem. On the axle, If 1/4” plate is not strong enough, use 3/8”. If that’s not strong enough, use 1/2”. On the frame, you may have to use a plate to spread out the force. Of course the shock company would build the shock to hold up. It just seems to me one mount on the axle and frame at each corner to handle spring, shock and bump is a nice clean way to do it. (Assuming coil overs)

On your discussion about rebound dampen, I’ve never understood the logic of increased damping on rebound. It seems to me that when you travel over washboard, you are eventually riding on the bump stops. I live on a dirt road and I think I’ve experienced this In my Bronco. The beginning of the washboard is not bad, but after 20 feet, I feel like I’m on the stops. I assume that you are correct because everything I read says the same, but I sure would love to have a completely adjustable shock (both compression and rebound) and do some testing. I know there are adjustable shocks , but I don’t want take them apart. I would like adjustment knobs or some such.

Sure if everything is strong enough you can run internal hydraulic bottom out.

On wash-boards (corrugations, ripples, etc), you can have packing or jacking depending on the amount of compression and rebound damping you have in that speed zone.
If you've got packing then your low speed rebound damping is greater than your low speed compression.
If you've got jacking then your low speed compression damping is greater than your low speed rebound.
A good tuner will give you the right balance between the two to keep the suspension up over washboards without screwing up the bigger bump response.

Suspension tuning gets very complicated very quickly.

Shock adjustments don't do the same as internal tuning. The adjusters effects are limited and each one will affect the shock in unintended ways. Like closing rebound adding more compression damping, low speed and high speed compression are inter-dependent and the check valves on each can get ugly at the limits of operation.

 

[Dougal]

The plots show here are CVP or "Football" plots. They show the shock forces in compression and extension as it goes around a cycle on the dyno. Max compression speed is top, max compression position is right, max rebound speed is bottom, min compression position is left.

There are two plots here from two very different shocks. The green is a standard gas-hydraulic single-tube shock. The same one I showed above in red as the force vs velocity.

The red plot is an OME shock with internal bypass circuits. You can see them being activated as the 3 different bypass circuits get activated at about 5, 25 and 40mm into the stroke on the right side of the graph.

 

[bdkw1]

RE jacking/packing. This is why I'm am generally against flutter stacks on only one side. It essentially provides directional bleed and can lead to jacking/packing in small chatter. If your going to run a flutter to help out with low-speed instead of going full sloppy with the bleeds, do both sides.

Reb forces..... I had Rick Haslow who was Mickey Thompsons shock guy tell me that reb produced more heat than comp in a shock. I never got a complete explanation of this from him. It seems very counter intuitive when you have a 20 stack on comp and 8's on reb. Reb is a known constant force. Comp can vary widely. In the big bumps, comp gets way more of a workout.

 

[Dougal]

RE jacking/packing. This is why I'm am generally against flutter stacks on only one side. It essentially provides directional bleed and can lead to jacking/packing in small chatter. If your going to run a flutter to help out with low-speed instead of going full sloppy with the bleeds, do both sides.

Reb forces..... I had Rick Haslow who was Mickey Thompsons shock guy tell me that reb produced more heat than comp in a shock. I never got a complete explanation of this from him. It seems very counter intuitive when you have a 20 stack on comp and 8's on reb. Reb is a known constant force. Comp can vary widely. In the big bumps, comp gets way more of a workout.

I've never heard the "flutter stack" term. Is it a very soft first stage?

Heat is energy absorbtion. On a dyno the shock is forced to move the same speed in both directions so the rebound generates around twice as much force and heat (heat being force*distance) as compression becaus the rebound damping is about twice as much.
On the trail your compression speeds can be 4x rebound speeds so heat generation is much more even. It all depends on your vehicle and terrain.

MTB it's no problem at all to surpass 6m/s compression. But the rally guys tell me 1m/s is about it and the tarmac guys about half that. Step through those three applications and you go from very little compression damping, through lots of compression damping to huge amounts. Rebound speeds on all of them aren't that different.

 

[bdkw1]

Flutter stack... sticking a small diameter shim between the face shim and the second shim. This provides soft initial rate till the face shim contacts the rest of the stack. It's kinda of a controlled bleed.

Edit, pretty much the exact opposite of digressive valving.

 

[Treefrog]

Hopefully some of these animations can support some of what is being said. All of the animations are modeled with a 1 lb mass on a 1/10 lb/in spring with damping ratio being the shock input. The mass is acted on by gravity, a spring, and a damper. It is a single spring mass damper system. No tire modeling going on. Displacement is relative to the flat road elevation.

First 2 plots up: A sweep from a damping ratio of 0 to 5. The first animation shows displacement; the second one shows the mass velocity, the mass acceleration, and the forces applied by the shock and damper. The mass starts at the uncompressed spring.

Third animation is of 3 systems with the damping ratio changed. It is isolated data from the first plot.

Fourth plot is changing rebound and compression separately. The mass starts at the uncompressed spring. Stiff is a damping ratio of .5. Loose is .1.

The fifth animation shows hitting a surface oscillation with different rebound and damping. It starts from equilibrium.

Last but not least, number 6. A 5 inch change in ground height. It starts from equilibrium.

 

[AgitatedPancake]

Basically the amount of damping force required to achieve a fast and stable rebound is way higher than most people appreciate.

Have you ever driven a vehicle with a blown shock or broken mount? They're completely uncontrollable in any dynamic situation. Even in a relatively stable situation of driving down a straight road the bounce and wallow is incredible.

Springs absorb and return bump energy. If you don't damp out that energy in the shock on compression and rebound you're in for a bad time. Uncontrolled rebound will have the inertia of the unsprung weight (wheels, hubs, axles, swingarm) destroying your shocks in short order. That's on top of the vehicle being unstable.

Awesome input, thanks! I have definitely encountered failed shocks on coil sprung vehicles and how much energy stays in the system with the spring just happily oscillating along not dissipating much . Those are good times hah. I do have more questions about the context of the expected rebound forces you describe though, is that in the context of a vehicle with a multi-hundred lb/in wheel rate (spring rate @ the wheel) and minimal unsprung mass? If we shift to the context of a trophy truck with a sub-100lb/in wheel rate and more unsprung mass, it seems like the required rebound forces would be notably decreased? At least based on the much lower spring rate and in turn, less stored energy at full compression.

Not to say that trophy trucks are what we're shooting for or anything, they're just one extreme end of the spectrum. While they excel in the desert, they definitely don't have street comfort and body stability of any sort on asphalt hah.

The plots show here are CVP or "Football" plots. They show the shock forces in compression and extension as it goes around a cycle on the dyno. Max compression speed is top, max compression position is right, max rebound speed is bottom, min compression position is left.

There are two plots here from two very different shocks. The green is a standard gas-hydraulic single-tube shock. The same one I showed above in red as the force vs velocity.

The red plot is an OME shock with internal bypass circuits. You can see them being activated as the 3 different bypass circuits get activated at about 5, 25 and 40mm into the stroke on the right side of the graph.

Very cool chart. Crazy how much rebound force that Dobinson is making. I also find it a little surprising that the bypass zones of the bypass shock are active in both directions. Are those created by auxiliary pistons like the Black Hawk from the above video? Just shooting from the hip, I think of bypasses in the context of "traditional" internal and external bypasses with essentially check valves on each bypass path making them active in only one direction (somewhat?). But as I see more devices like that Black Hawk, I'm understanding how those zones can be active in both directions

Flutter stack... sticking a small diameter shim between the face shim and the second shim. This provides soft initial rate till the face shim contacts the rest of the stack. It's kinda of a controlled bleed.

Edit, pretty much the exact opposite of digressive valving.

Just for my own noob clarification on more details of flutter stacks, how directly do they correlate to additional free bleed? Does the extra flow of a flutter stack happen at slightly higher piston velocities because you still do have the face shim providing a little bit of resistance, or is that basically an unnoticeably low amount of force?

Hopefully some of these animations can support some of what is being said. All of the animations are modeled with a 1 lb mass on a 1/10 lb/in spring with damping ratio being the shock input. The mass is acted on by gravity, a spring, and a damper. It is a single spring mass damper system. No tire modeling going on. Displacement is relative to the flat road elevation.

First 2 plots up: A sweep from a damping ratio of 0 to 5. The first animation shows displacement; the second one shows the mass velocity, the mass acceleration, and the forces applied by the shock and damper. The mass starts at the uncompressed spring.
-
Third animation is of 3 systems with the damping ratio changed. It is isolated data from the first plot.
-
Fourth plot is changing rebound and compression separately. The mass starts at the uncompressed spring. Stiff is a damping ratio of .5. Loose is .1.
-
The fifth animation shows hitting a surface oscillation with different rebound and damping. It starts from equilibrium.
-
Last but not least, number 6. A 5 inch change in ground height. It starts from equilibrium.

Ok these are incredible for explaining and visualizing overdamping, underdamping, and critically damping. Thanks for bringing the tech as always . In the fourth plot, am I reading correctly that compression are the negative numbers, and rebound are the positive numbers? Just to make sure I'm grasping it correctly. In the sixth plot, can you help me understand what I'm seeing a bit? It starts at equilibrium (ride height) which makes sense, then at 1 second undergoes an event that displaces the suspension -0.7" (loose), it starts damping that out then at 2 seconds it encounters another event that displaces the suspension +0.5" ish, then finishes the graph by damping that motion out?

 

[bdkw1]

Just for my own noob clarification on more details of flutter stacks, how directly do they correlate to additional free bleed? Does the extra flow of a flutter stack at slightly higher piston velocities because you still do have the face shim providing a little bit of resistance, or is that basically an unnoticeably low amount of force?

It's not free bleed per say but more flow at lower shaft velocities. Unlike free bleed, there is a slight amount of damping there. It can move your curve up without getting super sloppy like having all the free bleed holes open. You can play with the face shim thickness, the flutter space thickness/diameter to tailor the curve. Since it is directional, you can have separate curves for comp and reb. More useful in single shock setups than CO/BP combos.

 

[Treefrog]

Ok these are incredible for explaining and visualizing overdamping, underdamping, and critically damping. Thanks for bringing the tech as always . In the fourth plot, am I reading correctly that compression are the negative numbers, and rebound are the positive numbers? Just to make sure I'm grasping it correctly. In the sixth plot, can you help me understand what I'm seeing a bit? It starts at equilibrium (ride height) which makes sense, then at 1 second undergoes an event that displaces the suspension -0.7" (loose), it starts damping that out then at 2 seconds it encounters another event that displaces the suspension +0.5" ish, then finishes the graph by damping that motion out?

I don't quite understand what you mean about the fourth plot.

For the sixth plot, at one second it goes up a ramp at 5 in/s for 1 second. The plot is showing the difference between equilibrium for the ground height at that time and where the mass is. Here is the same event relative to absolute.

edit: Replaced Gif with one with correct mass and spring rate

 

[AgitatedPancake]

It's not free bleed per say but more flow at lower shaft velocities. Unlike free bleed, there is a slight amount of damping there. It can move your curve up without getting super sloppy like having all the free bleed holes open. You can play with the face shim thickness, the flutter space thickness/diameter to tailor the curve. Since it is directional, you can have separate curves for comp and reb. More useful in single shock setups than CO/BP combos.

Crystal clear, thanks for that clarification

I don't quite understand what you mean about the fourth plot.

For the sixth plot, at one second it goes up a ramp at 5 in/s for 1 second. The plot is showing the difference between equilibrium for the ground height at that time and where the mass is. Here is the same event relative to absolute.

edit: Replaced Gif with one with correct mass and spring rate

Ahh on the fourth one, I had to reread the context you provided again, I didn't interpret "The mass starts at the uncompressed spring" correctly this morning, but I completely understand now. The top of the chart is 10" of "droop" (for discussions sake), and the bottom of the chart at -10, is 10" of compression (assuming 0 is ride height). My mind just intuitively wanted to assume positive numbers were toward full compression and negative numbers toward full droop, but it's irrelevant really. Just happy I get it

On the sixth one, thanks for giving the absolute chart now as well, that one took me a second to interpret as well but I get it now, showing how each force curve kinda "lags" behind the amount of input movement as they dissipate the forces differently

 

[cervelorod]

I'm a suspension engineer with my own dyno

I would love to have or have access to a shock dyno. Perceived setting changes can be so subjective, it would be great to have hard data to correlate with. I’d like to do more SXS and snowmobiles, that’s a bigger market for me, and not just buy new shim stacks from Mfg’s to swap in.