About dampers in bump vs rebound

For #3 I didn't understood the question. Like if I was limited to the suspension tab screen. The bump value affected more than the rebound value. Spring rate is kind of cheating as it is also part of the damper.
No a spring is a spring and a damper is a damper. Combined they form what you would call a "shock absorber" (in general terms).

There are shock absorbers with out springs (not true, but). They use the cavity inside the shock as a gas spring (air, nitrogen, probably others gases as well that I don't know of). The cavity is there for the damper not to hydrolock (oil is not compressible). In those cases the cavity (bladder, Internal floating Piston...) acts as both the expansion chamber for the oil and as the spring. You can tune this by altering the size and pressure inside the cavity. I once modified a FOX DHX 5.0 mtb shock and reduced the cavity to create a more progressive feel to compensate for the linkage in the frame. It worked really well.

#4 I don't understand that answer
The values in the setup menu don't represent a unit. Changing from a 1 to a 3 could mean that you open 2 extra holes in the valve to get a total of 5 (since base was 2). It could also mean that you increased the thickness of the shims in the valve.
They are just numbers representing unitless damper values in the cars ini-file (correct me if I'm wrong on this).

I don't understand this. When weight is coming off the front wheels under acceleration, isn't the effect of the damper governed by rebound rather than bump stiffness?
I started thinking about this and the more I wrote the more IFs and BUTs I fond so I stopped. I think you are all right in that both rebound and compression affects the car. How much is dependent of all the IFs and BUTs that I wont write.
I would recommend you to test the specifik car at the corner and see what works best in just that situation. The krux is that when turning the weight shifts to the outside wheel, how much (enough to create a downward movement and engage CD or not) is the relevant question.

 

Friction coefficient doesnt equal to grip. Grip is friction coefficient times load...

 

Accordingly, grip increases with load. Which is what I was trying to say because someone stated the exact opposite.

 

Here is an example of a damper that has position sensitive valves (not to mix up with speed sensitive valves) and also the overdamped rebound feature at maximum travel to prevent bucking that I mentioned before.

 

So much stuff is going on, videos, documents, assumptions, etc.
I would like to fix a couple of concepts not very clear in this discussion.

1) Damping affects wheel natural frequency (natural = undamped)
If fd is the damped frequency and fn is the undamped frequency of the spring-mass system, they are related as follow:

ζ = damping ratio = damping coefficient / critical damping coefficient = c / (4*pi*fn*m)

Though for structures without dampers that rely only on internal damping (frictions, materials, etc.) where the damping ratio is low (<= 20%) the damping effect on frequency is negligible, we can see that with damping ratios more than 40% there is an important reduction of the natural frequency (>10%) , at 80% the reduction is 40% that decrease more and more near to critical damping.

2) Damping drammatically affects wheel oscillation amplitude
If we consider a unit pulse acting over a single degree of freedom spring-mass-damper system, calling u0 the amplitude of the oscillation, a relation exists between this amplitude and the damping ratio.
Here in this graph the amplitude is adimensionalised in relation to the product (mass x angular natural frequency)

This effect is never negligible, even at low damping ratios:
20% ---> 25% less amplitude
40% ---> 40% less amplitude
80% ---> 60% less amplitude

 

This thread is a hot mess. I know everyone is smart but you guys keep writing sentences that I have to read few times just to get over the smartness. It would be nice if I read something simple to understand. And don't spew out thrash just to sound smart.

Anyway, Kunos has a very simple tooltip where you hover the mouse over the adjustment window and it gives us the desired effect of such adjustment.

 

I absolutely agree with this. What makes it too difficult to get your head around this is that pieces of information taken from different (and sometimes even from the same) sources often seems to contradict each other and you don't even know which one is correct. Here's an example:

Well, this feels logical to me as stiff dampers make the suspension more rigid and absolutely rigid suspension transfers the load instantly. So far so good.

But if you read that dampers chapter from FSAE book you will see this at the bottom of page 23:

This one I do not understand, though it comes from a textbook for vehicle engineers so it is probably correct, but go figure. I would appreciate if somebody explains this to me.

Another confusing example is question #5 (front bumps during corner exit) and the answer posted by @Georg Siebert that makes no sense as fronts are not being compressed during corner exit.

 

Interesting read in this thread. Most of it going over my head though.

Care to explain what does this mean?

 

How about this.

 

I don't think they contradict each other. It's just that you can either lose grip by having too stiff suspension as well as by having suspension that's too soft. Too stiff will make the car unable to adapt to the surface and therefore not use all available grip, too soft and the car will transfer too much weight which will unsettle it. What you want with setups is always a good compromise.

If you guys are new to setups, I suggest this guide: http://www.racedepartment.com/threads/the-21-steps-guide-from-gtr2.99873/
It was created for GTR2 but a lot of it will translate to AC.

So let's say you're losing grip during braking, you can then soften the front bump, but if the suspension is already too soft, then simply increase rear rebound. That will give almost the same effect.
It's all on that guide: First you see if the car is overall too wobbly or too nervous, after you set that up you set the front/rear balance. The most important and most difficult part is practicing enough to be able to feel al those differences on the car. You can have all the knowledge you want, but it will be useless if you don't have enough consistency and feel to know what's wrong with the car and what changes with each setting.

 

I'm pretty sure the FSAE quote refers to the compression of the spring. This way, it makes sense again: the spring compresses too little because the damper is too stiff.

 

We're not talking here about adapting to uneven surface which is the job of fast bump/rebound settings as far as I understand. We're talking purely about longitudinal weight transfer caused solely by the car's deceleration. If you imagine that the surface is flat and the car has no suspension (like a TV stand on casters) then when you brake the load is shifted to the front instantly. If there's a suspension it will take some time required to compress front/extend rear. The amount of compression/extension (for any given deceleration) mostly depends on spring rates (softer springs - more displacement) but the speed of that movement (and thus the total time to compress/extend) mostly depends on dampers. The softer the dampers are the faster the movement is and less time is takes for load transfer to happen which means stiffer dumpers make this process longer. And this matches the FSAE book.

On the other hand, an extremely stiff damper will work close to a solid steel rod and will help transferring the load instantly. I think I might getting to understand this, what the book says applies to damping ratio being within certain useful bounds, ruling out extremely stiff (ratio >> 1) case.

But that would also mean that what @LeDude83 said in the beginning (about softening front bumps in case of understeer on braking) is invalid.

 

Eeeerm no. The book and me are saying the same thing. Read above.

 

Pretty sure it is not talking about the springs. The whole chapter is about dampers. And here's another thing. Later they say this:

Clearly they are talking about damping ratio and not spring movement. The first case is illustrated by the Impreza video here. The second case is also easy to imagine because if the rears are too lazy to extend due to being overdamped the wheels will lift off the ground (ever did a reverse wheelie on a bike?).

 

All these statements are in line with what I'm claiming.

 

Care to explain? They say that softening dampers speeds up load transfer and stiffening them slows down it. You're saying the opposite at least in regards to the braking phase.
Once again, the book:

Your words:

How anyone can think this is the same I beyond my understanding. And no, they do not mean the amount of spring compression/extension there.

 

Screw dampers, I'll never find out how to set them up

 

This all might makes sense if they are looking at the case of damping ratio < 1 (and they do say somewhere in that chapter that a typical value for a Formula SAE car is 0.5-0.7) and you're talking about the case when it is > 1 (which is often used for race cars with aero, like GT3)

 

Are you screwing them clockwise or anti?

Either way, someone will tell you it's wrong.