figgie said:
sorry dude.
to get pre-load correct you need to know the exact force that is being exherted when pre-loaded. No guessing is allowed. That means specific measurements of the spring rate from zero load to x+(n-1). Anything else is just a quandary in futility. once that is dialed in regardless if the pre-load is zero or another value (since preloading does affect the initial energy storage) then and only then can everything else be setup.
As for dampning, rebound, compression and valving. Unless you are that gentlman from SF that does this for bilestien themselves, I will lean his way on the knowledge front which is where I got all my suspension info and he was the one that informed me on the preload fiasco. Of course I am not one to lay my eggs all in one baskets so,
queried Porche Cup GT racers suspension folks,
Bosch Motorsports (extremly liberal with divuldginh information)
and a whole slew of other folks
all came back with
pre-load must be known to setup the rest of the system on the shock.
Measuring the spring and calculating pre-load IS knowing.
Putting the coilover/shock component into a shock dyno is also knowing.
I never said that it was good to adjust both rebound and dampening at the same time. As a matter of fact. I think most coilovers should delete that feature as most folks that buy the coilovers have zero clue what they are doing and definetly do not adjust that on a shock dyno or have numbers from a shock dyno to adjust those settings properly. I myself, if i were doing it again, would either do
a custom Bilstein setup
Custom Penske setup
and that is about it. Price is the only issue with either of those with Penske being on the absurd side.
Well you seem to be the kind of person that just takes info from people and repeats it. There is no explanation of how preload affects the valving or why, you're just saying that other people said you have to consider preload when setting up the suspension. I never said you don't have to consider preload into the whole setup, I just said that you don't have to adjust the valving because of preload. So explain that to me and we can have an intelligent discussion, otherwise I don't want to waste too much time on you. And the fact that you keep saying "rebound and dampening" just loses you all the credibility that you could've had if you tried a little harder to sound like you knew what you were talking about.
As for preload, it is something that needs to be known. But it has more to do with available shock travel and can aid in corner balancing, but again, the valving doesn't need to be changed. Think about what calls for a damping change. A change in spring rate, a change in mass either sprung or unsprung, a change in any of the other springs (arb's, tires, etc). This is neglecting track and driver tweaks. So how does preload change any of those? Unless by adding preload, you are adjusting your corner weights and adding or taking away weight at that corner, there would be no reason to adjust the damper. And just to be clear, we're talking about linear springs with a constant rate.
But when you say you talked to all these other people, are they considering preload the same way you and I are discussing it at this point. With preload meaning the amount of force stored in the spring when the suspension in completely unloaded? Because unless the preload force in the spring is greater than the force that the vehicle exerts on the spring, then preload doesn't mean anything. It just affects travel at that point.
Say you had a front suspension with a shock/spring installation ratio of 1. You were running a 500lb/in spring. The front corner weighs 1000lb. So static compression would be 2", so the spring would compression 2" and the shock would compress 2". But now you add 1" of preload to the spring while the car is in the air. So now the spring is compressed 1". So now when you put the car back on the ground, the first 500lb doesn't move the spring at all because of the preload, but the next 500lbs moves the spring 1". So now you have the spring compressed 2" and the shock only compressed 1". Now say you added another 1" of preload, making it 2" of preload. When you put the car on the ground, the spring and shock won't move at all. But the spring is still compressed 2" but now the shock isn't compressed at all.
Now the position for the damper would matter is the damper was displacement sensitive, but for arguments sake, we will neglect the small gas force and say that there are no forces acting on the damper when it is not moving. So the damper only generates any force when it moves.
But now all these people you talk to, what do they consider preload? Are they using the same definition? And are they using double height adjustable coilovers so that adjusting preload isn't the only way to get the car to balance out correctly? If they are using single height adjustable setups which is what I'm assuming, then their outlook is going to be different. Because they need to adjust preload to get the car to balance, but with a double height adjustable setup, you can independently set preload and overall height.
Who is this guy on SF that you're talking about that does this for Bilstein?
And in your previous post, you said "thankfully" when talking about how most cheap dampers adjust rebound and compression at the same time. That made it sound like you thought it was good. And you don't really need numbers from a shock dyno to be able to dial in the dampers. You just need a good driver and someone who knows how to interpret driver feedback into what needs to be changed. Although it does make things easier if you have shock dyno information, but that's only if people know how to read a shock dyno and relate it to the system in question. But those kind of people are few and far between. But I've done it both ways and it's not hard if you know what you're doing.
As for the custom setups. A custom Bilstein setup, isn't that expensive. There are many ways to do it quite affordably and come out with an amazing setup. I should know, I've done it.
And if you're going to come back and try and tear apart what I'm saying, could you please have something to back it up. Not just something you overheard or read on the internet somewhere. Maybe something you actually learned or tried yourself. It would make this discussion go a lot smoother. Thanks.
Tim
