Re: Coil-over shocks LONG REPLY

[Brendan Rudack <rudack@ucsub.Colorado.EDU>]

On Mon, 2 Jun 1997 STEADIRIC@aol.com wrote:

> >I am interpreting "low and high speed damping" as a function of piston
> >velocity within the damper.  Are you saying that this extra friction
> >from the coil-over will
> >cause the dampers to "fade",  what other problems might arise?  Is the
> >problem too much heat? My inquiring mind wants to know...
> 
> Yes that is part of the problem

What is the rest of the problem?  I suppose we can further break this down
into the type of damper being used.  If a Bilstein gas damper is used
won't the likeliness of "frothing" of the oil and "fading" of the damping
be less of an issue than with a Koni twin tube for example?  

> >That may be true but with my resources and especially my rather "shallow"
> >pockets, the coil-over setup was the way to go in order to gain what I
> >wanted out of my car. 
> 
> Incorrect.  Everything that you gained could have been achived without 
> resorting to coil overs, and for less money.

How Eric?  I feel that my car is *much* more responsive at ride heights
below stock and that is currently the stance my car has.  However, the
reduced ground clearance stinks in Colorado and Michigan winters I have
had to deal with.  Therefore, I enjoy the ability of increasing the ride
height when the white stuff falls.  How could I have done this without
building a threaded collar-type suspension?  Lastly, I found all springs
available to me on the "market" to be softer than my liking. I would
probably have preferred to go with softer springs and adjustable A/R bars
but again, that was not cost-effective.

> Some folks think that there is some sort of magic to keeping the car at 
> stock ride height while increasing the spring rate, they are wrong.  The 
> only thing keeping them from putting the ride height where they want it 
> is a lack of understanding of how to do it.

No magic at all Mr. Fletcher.  What you said is rather vague but I am
assuming you are implying there is some "sweet" spot below stock ride
height.  Let's say you have achieved this said "sweet" spot.  Do you not
see it as a compromise when you pull into a steep driveway and scrape the
huge front or rear overhang the 44 cars have?  What if the performance
achieved at this said "sweet" spot can be matched at stock ride height,
would it not then be a more "streetable" setup from that standpoint?
There may be tradeoffs in ride comfort in this case but it is what the
particular vehicle owner wants and will tolerate, right?
 
> >Personally, I
> >have my car lowered quite a bit (No, I don't have a bump-steer problem)
> >and if I wish I can raise it up for the snow season with minimal effort.
> 
> Yes you are. You just don't know it. It's Geometery and it can't be 
> changed inexpensivly.

I don't see it as being expensive to make camber/castor plates for the top
of the strut.  Wouldn't changing the castor effect the bump-steer
characteristics or would the degree of change need to be greater than
permissible
by strut top adjustments?  Again, I do not have a bump steer problem, the
car remains tractable over road irregularities while the suspension is
loaded and it remains stable under braking.  Sure bump-steer takes place
but it doesn't upset the dynamics of the chassis unless the irregularity
is large enough.
 
> >QSHIPQ> >expensive, try buying just the springs from any of the "kits".
> >> Eibach's ERS
> >> >springs are off the shelf, linear rate springs available in a universal
> >> 2.5in
> >> >dia, and you can spec the effective length in 2" increments and the
> spring
> >> >rate in 25lb increments, and relative to ANY kit available elsewhere,
> they
> >> >are price competitive for audis.  
> 
> Ahh, but this is where QshipQ is showing a lack of understanding.  Those 
> "Linear" rates are actually Falling rates.....

Meaning that if we were to graph load vs. wheel deflection for a
particular "linear" rate spring (ie. 200 lb/in) we would not see a linear
relationship but a curve with a downward concavity?

> >You forgot to mention that there is a progressive rate ERS setup
> >consisting of 2 seperate springs, Anyone BTDT?  
> Now your getting into SERIOUS tuning and with that comes expense, just 
> where do you set the cross-over?  Test, test, test.  But yes it would 
> work better, that's why I chose it.

Chose a progressive rate setup, right?  Are we saying that a progressive
setup is best suited for street use only and possibly the bumpiest of
tracks?  
 
> >From my limited experience I don't see an easier way to adjust corner
> >weights than to vary the ride heights. 
> I'm just varying rideheight's just doing it differently than using a 
> threaded coller.  Besides on a street car you'd be lucky to feel 100lbs 
> cross weight.
 
Are these the spacers QSHIPQ was referring to at the beginning of this
thread?  If 100lbs cross weight variance is not noticable in a ~3300 lb
then it is a moot point, afterall, these are street cars we are dealing
with.  We are both arguing the same thing, just attacking it
differently... 

> >What does it require?  Is the alternative cost-effective???  
> 
> Yes there is but once again it's experience and knowing WHAT the problem 
> is not just throwing parts at it.

You keep tip-toeing around the question, is the alternative top-secret?
So, if we do know WHAT the problem is and a solution is brought forth,
engineered, tested and proven worthy is it a bad solution?  I don't think
so.

> >Agreed. Scott, care to explain that one a bit better, I didn't quite
> >follow.  However, driving a highly modded 44 on the track with a coil-over
> >brought smiles to my face all day.  Especially since I am not familiar
> >with the 44 chassis and I was able to have a respectable "battle" with a
> >nicely prepped sticky tire equipped M6.....  The car became so easy to
> >steer with the throttle and so predictable with the addition of the ERS
> >"kit". 
> 
> Just because the car had coilovers on it does not make it superior.

I am assuming that you are complimenting my outstanding driving skills!
:-)  Maybe not superior but a heck of a lot better than any other setup I
have experienced to date.  And unlike our very own Trans Am chassis
engineer I haven't the opportunity to play with the "big" toys.  I guess
we are coming from to different perspectives.  I see it as what has been
accomplished and you see it as what still needs to be done.  


> > I can speak just as highly for my car.  It was running
> >consistently 3 seconds quicker around Stapleton than a H & R equipped
> >"chipped" 90Q 20v. I
> >have a 90Q 10v with a 2.5 inch exhaust. No other motor mods. Both cars had
> >the same tires,
> >same brakes and most importantly the same driver.
> 
> And without coilovers you would have the SAME results.........

I don't see how.  Are the factory bhp specs BS?  Stapleton is a very open
track that likes lots of power to gobble up the sea of concrete.  I am not
going to get into a hp guessing game but I can safely assume ~30 more hp
in the 90q 20v and from what I have read the weights of the 2 cars (10 and
20v models) are extremely close.  I realize that all the variables aren't
isolated but the odds for the 10valver are not for it...

Heck, I live in Michigan now, shouldn't I be working on a Rancho lift
kit for these roads...........

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Brendan Rudack

rudack@umcc.umich.edu
rudack@ucsub.colorado.edu
Fenton, Michigan 
USA

'88 90q
coil-overs, G60s, 63mm exhaust, 

'87 5000tq
IA stage 2, ABT/Koni/Tokico's

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