[A4] suspension theory thoughts, questions, etc - grooved shocks

[Grant Lenahan]

All you say is true (as usual).  Yes, you can raise the car -- and the 
top of the upper perch relative to the top of the spring. In the old 
days we called this "washers" :-)

But how does this load (as in, put stress on) the spring?

i dont believe it does.

if people mean something else by "pre-load" I suggest they use a word 
that is nto already defined in engineering.
'cuz they have me (and heretofore you?) very confused.

Grant
On Jan 11, 2007, at 9:08 PM, Huw Powell wrote:

>>   But on any setup where the lower perch moves on the strut body, the 
>> spring "distance" (whatever the heck that means - I'll assume you 
>> mean the spring length when under static load) is unaffected. As I 
>> have posted about 4 times now, the spring compresses from its open, 
>> unloaded length to its loaded length by an amount that is affected 
>> ONLY, repeat ONLY by the weight of the car and the spring rate. So 
>> this sounds to be wrong.
>
> I figured it out from one of the random posts on the subject.
>
> As we all know, moving the lower perch "up" raises the car (and vice 
> versa), because of what you say above - once the car is on the spring, 
> it will always have the same, more compressed than off the car, length 
> (x = kF).
>
> On a "one end adjustable" system, that's all there is.  On a 
> MacPherson setup, there is no adjustment, other than putting on 
> lowering (shorter) springs.  However, if the *top* is adjustable, it 
> actually moves the car body relative to the position of the entire 
> spring/shock assembly.
>
> Like, you could lower a car with MacP's by cutting the top strut mount 
> out and raising it relative to the car body, and welding it in it's 
> new place (probably through the hood by now).
>
> The only place this matters is, I guess, in what some are calling the 
> "pre load", which as far as I can see, only really affects how high 
> the car can bounce (or fly) before the suspension goes slack and the 
> wheel starts to leave the ground.  Soooooo, on a hard core race car, 
> cornering, the inside tires can be setup to maintain road contact, and 
> hence some semblance of alignment, and brake and power transfer, 
> longer before they "get air".
>
> At least, that's my understanding of something I will never actually 
> have to worry about in real life.
>
> -- 
> Huw Powell
>
> http://www.humanspeakers.com/audi
>
> http://www.humanthoughts.org/