Coilover Theory 101: Damper Valving
09-04-2018, 08:46 PM
#1
Coilover Theory 101: Damper Valving
Coilover Theory 101: Damper Valving
Note: Please excuse the long text and lack of images. I will update this post with relevant images shortly (showing the various parts that make up the damper valving)
We've all heard it before; "our dampers are custom valved.....etc etc". Coilover companies say it all the time, but what does it actually mean?
Well, aesthetics aside, let's break down a coilover from top-to-bottom (Note, when I say coilover, I am referring exclusively to the monotube variant):
- Upper Mount: The part that bolts onto your upper chassis
- Upper Perch: The part that compresses down on the coil spring
- Damper: More on this below
- Lower Perch: The part the coil spring sits on
- Locking Collars: Self-explanatory
- Lower Mount: The part that bolts onto your lower chassis/hub/knuckle. Can be fixed or a separate piece (I will not get into this here, as there are two sides to this with various arguments)
All coilovers, for the most part (i.e slight variations exist), follow this format. Why? Because there is only so much you can change in the design before it won't fit the intended vehicle.
When it comes to the Damper itself, again, for the most part, it follows the following format:
- Top Cap: Basically a dust cap and wiper to clean the piston rod as it moves in and out of the damper
- Damper Body: The casing. Can be steel or aluminium (double wishbone only. Never on MacPherson)
- Rod Guide/Seal Block: This guides the piston rod, making sure it moves up/down only with zero deflection. The longer the stroke/larger the piston rod, the more robust this needs to be. A good high-temperature seal must be used to prevent oil-leakage
- Piston Rod: The part that moves up/down, and is what connects/holds all the "valving" (may or may not be a part of it depending on the design, but usually is)
- Fluid: This is what the valving controls the flow of, and is responsible for the damping forces (compression & rebound). A good fluid is very important, as it needs to withstand high temperatures and cavitation
- Floating Piston: This is what separates the Nitrogen Gas at the bottom from the valving at the top. The seal used here is very important, as it must balance durability (prevent leaking, which can cause aeration) and friction (friction = heat = bad), while also withstanding high temperature. Viton is the defacto standard seal/o-ring
- End Cap: This may or may not be present, depending on the type of damper body. This is what keeps the Nitrogen Gas from escaping. There are generally two ways to fill the gas chamber: self-healing rubber (which uses a needle) and a schrader valve. A schrader valve allows more accurate pressure tuning (it does not leak after filling, unlike with a needle + rubber)
Ok, so now that's out the way, lets get back to the topic on discussion today: Damper Valving
When it comes to a set of coilovers and how they perform, this is single-handedly the most important aspect and can make or break a coilover kit. You can have the best fitting, best aesthetically pleasing coilover kit on the planet, but if the valving is wrong, then the coilover kit will ride like crap, plain and simple.
The valving generally consists of (I'm referring exclusively to adjustable dampers here):
- Damping adjuster: Usually a knob at the top of the piston rod, but can be at the bottom, side, inline etc
- Needle Rod: This is what is moved up and down the inside of the piston rod, controlling the movement of the bleed needle
- Bleed Needle: This controls the flow of fluid in and out of the bleed holes in the piston rod. Design is very important here, as a good design will smoothly control the transition, whereas a bad design is very inconsistent
- Jet Valve: This controls the flow of fluid in and out of the bottom of the piston rod. This can either have a check-valve for 1-way flow, or open for 2-way flow. The design of the check-valve is very important, as a good design will smoothly control the transition, whereas a bad design is very inconsistent
- All of the above relates to "bleed", which is what happens before any fluid flows through the Piston and Shims. The less flow through the free-flowing bleed system (i.e once it hits the bottleneck), the quicker the fluid is forced to flow through the non-free-flowing Piston and Shims (which is what controls the damping pressure)
- Piston: Various designs exist, with varying amounts of flow. The piston design directly affects the style of generated force, with the most common being Linear or Digressive
- Shims: These directly control the flow of oil through the piston (in one end, out the other). The diameter and thickness of the shims, and how they are stacked, is what ultimately determines the damping force. All shims function the same way, however, the quality of the shims used determine the consistency and durability
So what's the difference between good and bad valving? (Note: A lot of the following is copy and paste)
As mentioned already, having the correct Valving Profile for your particular application is the single most important factor that determines the comfort/performance of your dampers. In order to reduce development costs, a lot of manufacturers (in particular, the mass-market Taiwanese and South Korean manufacturers) use generic Valving Profiles based off of the chosen Spring Rate for each and every vehicle application. While this may initially seem like an acceptable practice, and for a lot of vehicles it does fall within the ballpark requirements (especially for the everyday street car), there are two reasons why this is inaccurate; Motion Ratios & Corner Weights
In laymans terms, what the Motion Ratios depict is how efficient your vehicle is in utilising the chosen Spring Rate, which determines the Valving Profile required. The closer to a 1:1 ratio (i.e the distance your piston rod moves vs the distance your wheel moves), the more your vehicle is utilising the Spring. The less your vehicle is utilising the Spring, the greater damping force required. To give an example:
For a given corner weight of 700lbs and a 6K Spring Rate
- A vehicle with a motion ratio of 1 would require 49lbs of damping force at a damper velocity of 1 in/sec
- A vehicle with a motion ratio of 0.5 would require 98lbs of damping force at a damper velocity of 1 in/sec
For a given corner weight of 1000lbs and a 6K Spring Rate
- A vehicle with a motion ratio of 1 would require 59lbs of damping force at a damper velocity of 1 in/sec
- A vehicle with a motion ratio of 0.5 would require 118lbs of damping force at a damper velocity of 1 in/sec
As you can clearly see from the above examples, for a fixed 6K Spring Rate, a simple change to the Corner Weight and/or Motion Ratio yields a different result for the required damping force. And because most vehicles have different corner weights and different motion ratios, this is the reason why we do not endorse the use of generic Valving Profiles based off of Spring Rate alone
Have you ever wondered why most Budget Coilovers for the early model (90's era) Japanese cars generally have acceptable comfort/performance, whereas for later model cars (and especially the European cars) the comfort/performance was abysmal? It's because the valving profiles for the early model Japanese cars were developed by the original Japanese Tuning Companies (e.g A'PEXi) before they outsourced the manufacturing to Taiwan and South Korea. After this happened, these mass-market coilover manufacturers, unable to develop their own valving profiles, simply used the same valving profiles that they were originally given by the Japanese Tuning Companies and have applied them to every vehicle application since!
DISCLAIMER: Budget coilovers have their place in the market i.e for those who cannot afford, or do not wish to spend too much money on a set of coilovers, but would still like a set of "performance coilovers". If you are only looking to spend a few hundred dollars, then basically any set of budget coilovers will meet you requirements. However, if you were looking to budget around $1000, may I suggest waiting a little bit, as $200-300 more can get you a custom-valved set of coilovers when caught on sale.
So how do you determine if a coilover kit really is "custom-valved", especially when all the budget coilover companies make this claim?
Generally speaking, any budget coilover company that claims to be a performance coilover company but does not have an in-house Shock Dyno for Testing & Development is NOT a performance coilover company, plain-and-simple (There are exceptions to this rule though. Some companies do have genuine partnerships with high-end suspension specialists, but then again, they are not budget coilover companies). All the budget coilovers companies currently on the market, they are simply just trading companies working off the back of a mass-market Taiwanese or South Korean manufacturer with no knowledge whatsover into the correct valving profiles required for each unique application. These are the companies that will use the same generic valving profiles on each and every vehicle because that's what their supplier provided them with.
How to determine this? Simply look at their catalogue. Any budget coilover company that has multiple vehicle applications listed in their catalogue can fall into this category. If they had the funds to properly develop the custom valving profiles for each of these applications, they have the funds to invest in an in-house dyno. "We partner with a suspension specialist who has a dyno" is an extremely poor excuse because the costs to do this would be far in excess of the purchase cost of a Shock Dyno! They are trying to hide the fact that they are simply just a trading company, and lack the knowledge and ability to tune their own dampers. Unfortunately, a large number of coilover brands fall into this category, whether they are from the USA, Europe or Japan. Buyer Beware...
So based on the above information, the best way to determine (beforehand) whether a coilover kit is good or not is to simply ask the manufacturer (or so-called) for a dyno graph. If they cannot provide you with one, generally you should steer clear.
If the manufacturer claims to offer "custom-valving", yet manufacturing is then outsourced for example to Taiwan, then they should still be able to provide you with a dyno graph as it is supposed to be custom-valving. If they do provide one, make sure the dyno graph is for your exact vehicle, for your specified spring rate. As damper valving is tuned specifically for the intended vehicle and specified spring rate, a generic dyno graph will not suffice as it doesn't actually mean anything.
Damper valving is very precise. Bleed needle profile, jet valve, needle shaft and needle adjuster all affect the valving just as much as the shim stacks do. It can be very difficult at times to match Damper A to Damper B consistently (which can only be determined on a Shock Dyno), even if the shim stacks are 100% identical, as even 0.5mm difference in bleed can generate a completely different result. So if these "custom-valved" dampers are being mass-manufactured to "custom specification" overseas, if they do not have an in-house dyno, how are they guaranteeing the dampers in your coilover kit are correctly matched? Their Taiwanese manufacturers most certainly don't have a shock dyno (and if they do, they are definitely not going to check each and every damper they make).
Footnote: Please feel free to share any dyno graphs that you have and wish to discuss/analyse. On my end, I will update this thread with various dyno graphs in my spare time from various different brands/manufacturers that get dynoed at our facility
Oh yeah, disclaimer no.2. I am known to be wrong at times, so if any information doesn't make sense or sounds wrong, don't hesitate to point it out and I can edit/update the information. We are all in this community to learn, and the more we share ideas/tests/data, the more everyone can benefit
Note: Please excuse the long text and lack of images. I will update this post with relevant images shortly (showing the various parts that make up the damper valving)
We've all heard it before; "our dampers are custom valved.....etc etc". Coilover companies say it all the time, but what does it actually mean?
Well, aesthetics aside, let's break down a coilover from top-to-bottom (Note, when I say coilover, I am referring exclusively to the monotube variant):
- Upper Mount: The part that bolts onto your upper chassis
- Upper Perch: The part that compresses down on the coil spring
- Damper: More on this below
- Lower Perch: The part the coil spring sits on
- Locking Collars: Self-explanatory
- Lower Mount: The part that bolts onto your lower chassis/hub/knuckle. Can be fixed or a separate piece (I will not get into this here, as there are two sides to this with various arguments)
All coilovers, for the most part (i.e slight variations exist), follow this format. Why? Because there is only so much you can change in the design before it won't fit the intended vehicle.
When it comes to the Damper itself, again, for the most part, it follows the following format:
- Top Cap: Basically a dust cap and wiper to clean the piston rod as it moves in and out of the damper
- Damper Body: The casing. Can be steel or aluminium (double wishbone only. Never on MacPherson)
- Rod Guide/Seal Block: This guides the piston rod, making sure it moves up/down only with zero deflection. The longer the stroke/larger the piston rod, the more robust this needs to be. A good high-temperature seal must be used to prevent oil-leakage
- Piston Rod: The part that moves up/down, and is what connects/holds all the "valving" (may or may not be a part of it depending on the design, but usually is)
- Fluid: This is what the valving controls the flow of, and is responsible for the damping forces (compression & rebound). A good fluid is very important, as it needs to withstand high temperatures and cavitation
- Floating Piston: This is what separates the Nitrogen Gas at the bottom from the valving at the top. The seal used here is very important, as it must balance durability (prevent leaking, which can cause aeration) and friction (friction = heat = bad), while also withstanding high temperature. Viton is the defacto standard seal/o-ring
- End Cap: This may or may not be present, depending on the type of damper body. This is what keeps the Nitrogen Gas from escaping. There are generally two ways to fill the gas chamber: self-healing rubber (which uses a needle) and a schrader valve. A schrader valve allows more accurate pressure tuning (it does not leak after filling, unlike with a needle + rubber)
Ok, so now that's out the way, lets get back to the topic on discussion today: Damper Valving
When it comes to a set of coilovers and how they perform, this is single-handedly the most important aspect and can make or break a coilover kit. You can have the best fitting, best aesthetically pleasing coilover kit on the planet, but if the valving is wrong, then the coilover kit will ride like crap, plain and simple.
The valving generally consists of (I'm referring exclusively to adjustable dampers here):
- Damping adjuster: Usually a knob at the top of the piston rod, but can be at the bottom, side, inline etc
- Needle Rod: This is what is moved up and down the inside of the piston rod, controlling the movement of the bleed needle
- Bleed Needle: This controls the flow of fluid in and out of the bleed holes in the piston rod. Design is very important here, as a good design will smoothly control the transition, whereas a bad design is very inconsistent
- Jet Valve: This controls the flow of fluid in and out of the bottom of the piston rod. This can either have a check-valve for 1-way flow, or open for 2-way flow. The design of the check-valve is very important, as a good design will smoothly control the transition, whereas a bad design is very inconsistent
- All of the above relates to "bleed", which is what happens before any fluid flows through the Piston and Shims. The less flow through the free-flowing bleed system (i.e once it hits the bottleneck), the quicker the fluid is forced to flow through the non-free-flowing Piston and Shims (which is what controls the damping pressure)
- Piston: Various designs exist, with varying amounts of flow. The piston design directly affects the style of generated force, with the most common being Linear or Digressive
- Shims: These directly control the flow of oil through the piston (in one end, out the other). The diameter and thickness of the shims, and how they are stacked, is what ultimately determines the damping force. All shims function the same way, however, the quality of the shims used determine the consistency and durability
So what's the difference between good and bad valving? (Note: A lot of the following is copy and paste)
As mentioned already, having the correct Valving Profile for your particular application is the single most important factor that determines the comfort/performance of your dampers. In order to reduce development costs, a lot of manufacturers (in particular, the mass-market Taiwanese and South Korean manufacturers) use generic Valving Profiles based off of the chosen Spring Rate for each and every vehicle application. While this may initially seem like an acceptable practice, and for a lot of vehicles it does fall within the ballpark requirements (especially for the everyday street car), there are two reasons why this is inaccurate; Motion Ratios & Corner Weights
In laymans terms, what the Motion Ratios depict is how efficient your vehicle is in utilising the chosen Spring Rate, which determines the Valving Profile required. The closer to a 1:1 ratio (i.e the distance your piston rod moves vs the distance your wheel moves), the more your vehicle is utilising the Spring. The less your vehicle is utilising the Spring, the greater damping force required. To give an example:
For a given corner weight of 700lbs and a 6K Spring Rate
- A vehicle with a motion ratio of 1 would require 49lbs of damping force at a damper velocity of 1 in/sec
- A vehicle with a motion ratio of 0.5 would require 98lbs of damping force at a damper velocity of 1 in/sec
For a given corner weight of 1000lbs and a 6K Spring Rate
- A vehicle with a motion ratio of 1 would require 59lbs of damping force at a damper velocity of 1 in/sec
- A vehicle with a motion ratio of 0.5 would require 118lbs of damping force at a damper velocity of 1 in/sec
As you can clearly see from the above examples, for a fixed 6K Spring Rate, a simple change to the Corner Weight and/or Motion Ratio yields a different result for the required damping force. And because most vehicles have different corner weights and different motion ratios, this is the reason why we do not endorse the use of generic Valving Profiles based off of Spring Rate alone
Have you ever wondered why most Budget Coilovers for the early model (90's era) Japanese cars generally have acceptable comfort/performance, whereas for later model cars (and especially the European cars) the comfort/performance was abysmal? It's because the valving profiles for the early model Japanese cars were developed by the original Japanese Tuning Companies (e.g A'PEXi) before they outsourced the manufacturing to Taiwan and South Korea. After this happened, these mass-market coilover manufacturers, unable to develop their own valving profiles, simply used the same valving profiles that they were originally given by the Japanese Tuning Companies and have applied them to every vehicle application since!
DISCLAIMER: Budget coilovers have their place in the market i.e for those who cannot afford, or do not wish to spend too much money on a set of coilovers, but would still like a set of "performance coilovers". If you are only looking to spend a few hundred dollars, then basically any set of budget coilovers will meet you requirements. However, if you were looking to budget around $1000, may I suggest waiting a little bit, as $200-300 more can get you a custom-valved set of coilovers when caught on sale.
So how do you determine if a coilover kit really is "custom-valved", especially when all the budget coilover companies make this claim?
Generally speaking, any budget coilover company that claims to be a performance coilover company but does not have an in-house Shock Dyno for Testing & Development is NOT a performance coilover company, plain-and-simple (There are exceptions to this rule though. Some companies do have genuine partnerships with high-end suspension specialists, but then again, they are not budget coilover companies). All the budget coilovers companies currently on the market, they are simply just trading companies working off the back of a mass-market Taiwanese or South Korean manufacturer with no knowledge whatsover into the correct valving profiles required for each unique application. These are the companies that will use the same generic valving profiles on each and every vehicle because that's what their supplier provided them with.
How to determine this? Simply look at their catalogue. Any budget coilover company that has multiple vehicle applications listed in their catalogue can fall into this category. If they had the funds to properly develop the custom valving profiles for each of these applications, they have the funds to invest in an in-house dyno. "We partner with a suspension specialist who has a dyno" is an extremely poor excuse because the costs to do this would be far in excess of the purchase cost of a Shock Dyno! They are trying to hide the fact that they are simply just a trading company, and lack the knowledge and ability to tune their own dampers. Unfortunately, a large number of coilover brands fall into this category, whether they are from the USA, Europe or Japan. Buyer Beware...
So based on the above information, the best way to determine (beforehand) whether a coilover kit is good or not is to simply ask the manufacturer (or so-called) for a dyno graph. If they cannot provide you with one, generally you should steer clear.
If the manufacturer claims to offer "custom-valving", yet manufacturing is then outsourced for example to Taiwan, then they should still be able to provide you with a dyno graph as it is supposed to be custom-valving. If they do provide one, make sure the dyno graph is for your exact vehicle, for your specified spring rate. As damper valving is tuned specifically for the intended vehicle and specified spring rate, a generic dyno graph will not suffice as it doesn't actually mean anything.
Damper valving is very precise. Bleed needle profile, jet valve, needle shaft and needle adjuster all affect the valving just as much as the shim stacks do. It can be very difficult at times to match Damper A to Damper B consistently (which can only be determined on a Shock Dyno), even if the shim stacks are 100% identical, as even 0.5mm difference in bleed can generate a completely different result. So if these "custom-valved" dampers are being mass-manufactured to "custom specification" overseas, if they do not have an in-house dyno, how are they guaranteeing the dampers in your coilover kit are correctly matched? Their Taiwanese manufacturers most certainly don't have a shock dyno (and if they do, they are definitely not going to check each and every damper they make).
Footnote: Please feel free to share any dyno graphs that you have and wish to discuss/analyse. On my end, I will update this thread with various dyno graphs in my spare time from various different brands/manufacturers that get dynoed at our facility
Oh yeah, disclaimer no.2. I am known to be wrong at times, so if any information doesn't make sense or sounds wrong, don't hesitate to point it out and I can edit/update the information. We are all in this community to learn, and the more we share ideas/tests/data, the more everyone can benefit
Last edited by YCW; 09-05-2018 at 09:05 AM.
The following users liked this post:
YCW (09-05-2018)
09-05-2018, 11:54 AM
#3
Looks like a Penske double digressive piston?
09-05-2018, 08:47 PM
#5
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masterthl
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