Shock Tech (Long read)

Old 07-12-2019, 08:05 PM
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Default Shock Tech (Long read)

I decided to put together all of the helpful resources I have found in my own quest to learn about suspension. This has been a long time in development and has spanned ownership of many cars and experiences I have had. While I certainly have my opinions it is my hope that the information I have gathered can help make for an easier and more informed decision without the same time sink I made.

Suspension tuning as of this posting, I see has little to no hobbyist / enthusiast discussion. That is of course outside niche communities such as offroad vehicles, motoX, and dedicated racers. Even then the discussion is often hidden away within forums and not regularly shared or made available for the average Joe to digest. Our aftermarket options, no matter the car are echoed based on brand loyalty, forum vendor participation, and general marketing for a product. The need is created little applicable knowledge is shared. You see "New technology" and "better performance" "race proven" etc with no details about what it is that will be changing on your vehicle to make it do what you want. This is evident by people unhappy with lowering spring brand abc, or aftermarket shock brand 123 and the posting on the forum asking about what is a better option. For those whom just want to reduce the request to "It needs to look good" or "I want it to ride comfortable / like a race car" that is completely understandable. Free time comes at a premium and you do not need to be a guru to make an informed decision. I would encourage you to at least understand how to best get what you want as it relates to vehicle suspension/ ride quality from this post.

If you like learning, or journeying down the internet rabbit hole, here is another forum post from 2010 attempting a similar goal as my own:

I realize this is a huge amount of information, and as it pertains to tuning shocks specifically is incomplete. Please let me know if there is interest to dig deeper into the tuning theory, or if the high level overview is sufficient.

Shock tech:

Shock Type/ Design:

Primarily in Motorsport and road vehicles Monotube and Twin Tube shocks are used.
Each have their own pros and cons, in my own opinion, and that of others Monotube shock construction has the potential to provide the best results.

-A monotube shock absorber is constructed using a single tube filled with oil and gas separated by a floating dividing piston. This prevents the negative effects of cavitation such as performance loss and suspension wear. As the piston rod and piston cycle through the hydraulic oil, the gas keeps the oil pressurized to prevent it from mixing with air and foaming up (cavitation).

-A twintube shock absorber has a main outer tube and a secondary inner tube. The piston rod and piston cycle through hydraulic oil in the smaller inner tube of the shock, pushing oil into the outer tube.

References of designs and cross sectional pictures:

Shock Valving:

The overall performance of the shock and the method by which you can tune what the shock is doing is by using certain piston and shim stack combinations. There are a few base choices that exist and produce different behaviors. You have Linear pistons, Digressive pistons, and Regressive pistons.

Linear Piston:

Digressive Piston:

Regressive Valving:

Their construction varies slightly but their shape and internal configuration results in the ability to control how much force is generated and when. You almost always see this represented with a force vs velocity graph which shows how much damping force is created at a moment in time per a given speed, usually in inches per second. Further more the shim stack and valving which can be placed on the compression, rebound, or both sides of the shock piston. Influence how the piston moves through the reservoir of oil.

Adjustable vs Non Adjustable:

Shocks are available in a wide variety from non adjustable to 4 way adjustable. The adjustments that can be made vary from setup to setup. A non adjustable shock can be designed to meet a target performance envelope. Beyond that you cannot adapt it while it is on the car. This does not mean that non adjustable shocks are bad, sometimes just having bells and whistles does not make what you have better than the next person. A typical budget aftermarket adjustable shock usually only lets you adjust rebound damping, however on these types of shocks when you change the rebound setting you almost always add to the total damping and compression is affected in some way, these would be your "1 way" adjustable shocks. I do cannot think of an instance other than budget reasons to choose this. "2 way" adjustable shocks get better, you are able to adjust compression and rebound independently and provided you know what changes you need to make can result in a good setup. "3 and 4 way" let you adjust low and high speed compression and rebound where you develop the "knee" or "knee speed" on the force vs velocity graph. This starts to matter for a pure race track setup, but benefits can be had on the street.

Shock Tuning:

Suspension tuning should be approached as a whole. Shocks contribute a lot to transmissibility so you (the driver) feel these changes the most. Shocks are designed and tuned with valving technology, shim stack configurations, shock body / reservoir designs and even bump stop/ bump spring configurations in mind. One of the key elements of tramissibility is the amount of vehicle pitch you experience, typically you do not want to feel pitch motion where possible. Normal design decisions in road cars (consumer cars) appear to take the approach that each manufacturer's race developed applications do, but without the context of what the car will be used for. For instance a lot of the harsh ride experienced in any car is almost always due to the behavior a car has where the suspension "Jacks down" in which shock does not reset to ride height before the next bump and slowly, or sometimes quickly the chassis gets pulled down onto the bump stops which can be described as an infinite spring rate. This article in which a Penske race engineer gives his observations as to why this is the case I think is very telling and is the perfect area to focus on improving ride quality in street cars today/{%22issue_id%22:470289, %22view%22:%22articleBrowser%22,%22article_id%22:%222991492%22}

6 one way, half a dozen another really applies to shock tuning. Here is another example to approaching shock tuning:

"General Shock Tuning Theory
Shock valving influences ride and handling, but these two things are often at odds with each other. Large amounts of low speed rebound will give you great cornering control but may cause the suspension to be harsh and may prevent the suspension from drooping out in the whoops. Because of this, it is best to run sway bars and tune the shocks for ride quality.

When selecting where to tune, be sure it represents the type of terrain you will encounter the most. Short travel can go surprisingly fast if you tune it stiff, but itĺll beat you up on the little stuff. On the flip side long travel suspensions can be plush and float over everything but it can be too soft leading to poor handling. Make sure you tune for the conditions you plan to see.

Shock tuning can be extremely rewarding, with a little work you can achieve tremendous improvements in ride comfort and performance.

How to tune a shock yourself:

Additional references:
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Old 07-13-2019, 02:57 AM
Indiana Jones
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Great write up, and I agree, this kind of information isn't readily available. Kudos for the post!
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Old 07-13-2019, 03:53 PM
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Shock Tuning - Theory and Strategy

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