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

[Huw Powell]

>   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/