Re: Coil-over shocks LONG REPLY

[STEADIRIC@aol.com]

rudack@ucsub.Colorado.EDU said:

>> >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?  

I'm saying that friction brings on a whole slew of problems.  The true 
designer/Engineer knows what these problems are and try's to accomplish 
his/her goals with the least comprmise's.  Once again EXPERIENCE.

>> >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?  

There are several ways. Just being a catalog picker and throwing parts at 
a car is'nt going to do it.

>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.

On the "little" chassis a adjustable roll bar is both easy AND 
inexpensive, Just gotta know what you want, what your looking for and 
where.

>> 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.  

No I'm not.  Where did you get that?  From this statement alone you have 
proved a lack of the basic's of suspension design.

>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?

See the above commnet.

>> >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?  

You need to learn more about bump steer.  Somewhere in the archives is a 
treatise by me on it, you should read it.  Caster has no (Ok Very, very 
little) effect on bump steer.  Bump steer is a steering rack, steering 
arm, Lower Control arm problem.

>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.

You do have bump steer, you even said so. There is now way of getting 
around it.
 
>> >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 springrate 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?

It's a geometery thing, time to hit the books.

>> >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?  

The progressive set is an excellent choice in all situations.
 
>> >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... 

Yes and no on the ride height adjuster's, they serve a purpose and qshipq 
does'nt understand enough what's going on back there to understand their 
purpose.

>> >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.

the alternative is not top secret, you just have to know what your 
doing..... EXPERIENCE how many times do I need to say it.

<Snippage>

>> > 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...

I did'nt say with stock suspension, I said without coilovers.

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

No need just design the mods correctly.......

Later!


Eric Fletcher S.O.C.
'87 5KCSTQ WAY too many toys
Trans-am/Sportscar Chassis Engineer
St. Louis, MO

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