Can anyone explain to a Ford driver what the difference is between the "valving" in a damper and what happens when you turn the knob and adjust compression/rebound?
What is actually happening inside the damper and how does that effect the wheel?
I'm not completely ignorant to the topic, I have torn down forks and installed Racetech Gold Valves and gone off the cheat sheet for the shim stack. I just don't understand the physics of it.
That's probably going to depend on the specific construction of the damper you're talking about. As far as i know there are several ways to accomplish it. One thing i can say for certain is that one difference between 'valving' and 'adjustability' in very general terms is that the damper will be built to be adjustable only within a given range, and how the range is determined and how the adjustment happens might be two totally separate things.
Smarter people will soon post, but as the shaft moves, oil is displaced through a "head" and past the shims, creating pressure differentials.
The shims are set up (I think...) so that the faster the shaft moves, the more force is generated.
The pressures are "tuned" to the spring rate and frequency, and all of it is affected by suspension attachment points and a number of other things.
Compression and rebound are the "up and back" movements, and require a certain relationship in forces generated a car to ride better or handle better.
A lot of math involved, and as much art as science, best I can tell.
Vigo said:That's probably going to depend on the specific construction of the damper you're talking about. As far as i know there are several ways to accomplish it. One thing i can say for certain is that one difference between 'valving' and 'adjustability' in very general terms is that the damper will be built to be adjustable only within a given range, and how the range is determined and how the adjustment happens might be two totally separate things.
This is pretty much dead on. The adjustment method changes by manufacturer and damper design. What the OP described about motorcycle forks is how most monotubes work (but not the only way). For twin tube stuff there's a few different ways you can do it. For example konis use a vavling system that includes a spring that applies pressure to the tension side of the valving. The adjuster changes the preload on the spring, making it easier or harder for the valves to be pushed open by flowing oil. I've also seen systems that have a bypass channel through the middle of the rod and the adjuster changes how much oil can bypass the valving/piston, and systems where the adjuster is covering/uncovering holes in the piston.
The latter is usually referred to as a bleed in my experience. Just in case you need a term that shock designers will recognize.
There's a pretty good episode of the Slip Angle Show podcast with Lee Grimes from Koni where he explains damping adjustments and what they mean to the car's performance, but that isn't explicitly what you asked for (damper internals).
It really depends on the type of adjustable shock though. Some of those adjusters do little, if anything.
That's a matter of design. You either get very fine adjustment or very broad adjustment. If you're building an almost-generic shock that will be used in a range of applications, you put in a lot of adjustment. If you're building a shock that's been valved for a very specific application and a highly sensitive/demanding driver, you make it fine.
I think the biggest difference (from what I'm gleaning that you're asking) from a functional standpoint is that the valving is a permanent (unless you rebuild them) change. The shape AND slope of the shock dyno lines (there's sometimes a "knee" where the shock "blows off" at higher shaft travel speeds), such as going from Digressive, to linear, to regressive curves, can be changed by changing the valving.
The knob adjustment (to my understanding) would only change the slope of the curve (or, part depending on what's adjusted) and not be able to change the overall behavior (major shape) of the shock.
Mechanically dampers are stupid simple, their effect is anything but. Get a copy of Paul Haney's "inside Race Car Technology" for me a non engineer it has one of the best explanations of how dampers work and how everything is interrelated. I too like to visualize whats going on inside the dampers so I know if a simple adjustment will get me where I need to be or it's time to have them revalved
Reading about a bit, I came across this website: http://farnorthracing.com/autocross_secrets6.html
GREAT Info, and a subset of what I was trying to say about the adjusters can be seen in the photo about rebound:
And the one about Compression adjustment:
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