Re: Just out of curiosity...

["I.Mannix" <mannix@privatei.com>]

>Jason Brunberg asked:
>
>> Hey volks!  I was talking to a fellow vdubber the other day who told
>> me
>> that with height-adjustable suspension on a vw, one must alter the
>> alignment every time the height is changed.

Well, maybe.....

>Nah!  You don't need to change the alignment after changing the ride
>height.  That would be ridiculous.  You know what you're talking bout
>Jason (unlike most people I know around here =).  The ride height does
>nothing to the angle of the wheels.

Sure it does.  The wheel is attached to the car via a dynamic triangle.
The wheel is attached to the hub, which is connected to the strut bearing,
which connects to the body.  The control arm makes the triangle.
Basically, the hub is connected to the wheel, which is fixed to the strut,
and the ball joint allows vertical motion along with the strut.  When the
suspension compresses beyond horizontal control arms, less negative camber
shows up.  The control arm's length does not change, and it is pulling the
bottom of the hub toward the car as the c-arm compresses.  So, if you start
with a car which has horizontal control arms, and lower it, the camber does
change.  It becomes less.  Changing ride height does in fact change wheel
angle.  It'll change toe slightly, too.  The end of the control arm moves
in an arc around its pivots, which is the reason MacPherson strut
assemblies have such lousy camber control - camber does change when the
suspension compresses, whether it is because the car hits a bump or you
move the lower spring perch.

Now, do you have to realign?  Well, maybe.  If you lower it beyond parallel
arms, it'll get positive camber and a bit more toe out.  If you raise it so
the c-arms are pointed at the ground, it'll do the same.  This whole thing
is why we always talk about having the control arms parallel with the
ground - it allows the most static camber, from parallel, you stand nothing
at all to gain.wrt camber preservation when the suspension moves, but it
gives the most initially.  I don't think it'd be necessary to change
alignments with subtle changes, but it might be worth checking if it
matters, IE, an autocross car.

  The only reason you'd change it
>would be to get more grip but that's the same with any suspension
>setup.  I still haven't done my alignment on my 16v because I marked my
>eccentric bolt and the alignment is perfect still!

It is not the same as it was, though.  A VW will go straight provided
camber is equal left to right.  Toe does not matter - your steering wheel
might not be level, but the car will center itself, whether toed in our
out.  By marking the eccentrics, you are ensuring equal angles left and
right, the angle of the strut vs hub, but as the ride height changes, so do
the wheel angles.  It'd be interesting to see exactly how much it changes,
ahh, I guess I could draw some pictures and get an idea, but that'd involve
measuring stuff.  Yuk.  Hope this makes sense!


Mannix






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