Re: Coil-over shocks LONG REPLY

[STEADIRIC@aol.com]

QSHIPQ@aol.com said:

>Interesting post.  Having done a couple coil over setups, I find the
>conclusions drawn above somewhat misleading.  

Unfortunally Scott your response is VERY misleading.....

>Coil-over is a packaging
>concept, but that is NOT all.  They do tend to bind when one picks the wrong
>effective spring length for the ride height chosen.  

Incorrect.  A coil spring is a torsion bar that has been wound into a 
helix, because of that a coil spring is ALWAYS trying to bind as it 
compresses and extends, put a damper in the middle of that and you get a 
sideload on the piston.  Sideload=Bind.  Your answer assume's mechnical 
bind when a spring stacks flat.

>Low speed damping
>control and high speed heat might apply to a race car with MASSIVE spring
>rates and low relative travel, not so the case with a more reasonable street
>car.  

Incorrect again, and the answer shows a lack of understanding of the 
terms "low speed damping" and "high speed damping".  A damper controls 
ocilations by converting the movment into heat, it's their job.  Add 
friction from the coil over design and you creating problems that can be 
avoided.  

>The main advantage of coil over design and application is the
>flexibility you have without having to custom wind any springs, 

Incorrect you don't have to run coil overs to get flexibility, if that 
was true how come Stock Car, Supermodified and other sedan based racing 
can get it right.

>that can get
>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.  

Personally in large street car I'd be running larger springs than a 2.5" 
Formula car spring.... If you don't understand the reason's go hit the 
books.

>Corner balancing a car for the track, changing ride height, linear rates,
and
>phenomenal handling make coil-overs a serious improvement for the audi cars.

NONE of that requires coil-overs.......

> All you need to do is drive one, take a lap time, and one will realize
that,
>even with all the "kits" available, this setup will do donuts around most
>others.  Not at the expense of ride control, height, or comfort or longevity
>either.  The street ride is not choppy, hardly unacceptable for the
>autobahners q's are known to be. 

Again none of that requires coil-overs.

>The long wheelbase and overhang, tame even
>some of the wilder coil-overs installed in audis.  

The overhang comment shows a lack of understanding here.

>Downside?  I find that most folks that have them on street cars, don't
change
>the height after the initial dial in.  Most have an idea on what and where
>they want ride height, and once the suspension is dialed in there, few
change
>the height.  So adjustability isn't really the advantage for "most" folks.

The Why question comes to mind then.

> Getting the proper spring length and rates, especially with the 44 chassis
>takes a lot of work, btdt.  

Rate's take work, length is easy...........

>The rewards are worth it, the decrease in the
>tail wagging antics of the 44 chassis alone brings smiles.  

Since understeer is the prevailing condition the "Tail Wagging" comment 
makes no sense.....

>On a related subject, a cousin of mine I talked to last weekend has an
>interesting job at Ford these days, that of suspension engineer.  We nerded
>extensively, and his summation, "we have all the programs available to give
>us an indication of suspension setups, but until we put it on a car and test
>it, the results are just paper."    He was also most facinated by the
>multilink rear of qship.  

Computer simulations are VERY accurate and telling, I'm not sure what 
your cousin is meaning, unless he's talking about big car "Comfort and 
Feel" which is subjective anyway.

>Bottom line:  Don't write off a mod until you've btdt. 

BTDT on several car's.  Would I do it on a track only car?  Depends.  
Would I do it on a street car?  Probally not.

>My experience, as Audi Chassis Engineer Emeritus, 

Now that's going a LITTLE far..........

>is that coil-overs are a sensible and decent
>alternative, in performance and price, to ANY "kit" currently on the market.
> Proper execution of the mod, any mod in fact, is what differentiates the
>good from the bad.  Lots of books and reference material available to anyone
>that wants it, several include workbooks that make you a post-graduate
>quickly.  

Once again going VERY Far.....  Especially the Post grad comment.  If it 
was easy we all would be setting up Indycars making some large 6 digit 
incomes.  That comment is the equivlent of telling someone that because 
they saw a doctor on "ER" transplant a heart they can do it too.  
Desiging suspension from the ground up is a excercise in compromise.  
Reengeneering an established design is tougher because you are not privy 
to certian other variables which can make large impacts in the final 
results.  

Reading books is a great way to get an understanding of terms and the 
realationships of certain variables. Will it make you a Post grad expert 
quickly?  Never.  That's why there are schools, and even once out of 
school it will still be trial and error until experience takes over. 
Experience is key though.

>Proper suspension setup is not rocket science.  

Your right it's not rocket science, as someone pointed out rocket science 
is somewhat understated  (What goes up must come down after all!)  
Suspension design is more along the line of Quantum physics.

>Understand the physics, and what you want the car to do, 

Which is the problem.  Most people want their cars to "Handle Better" 
what does that exactly mean?  Better transient response?  More mechnical 
grip at the front? At the rear? etc etc......  What's it going to be? 
Enter experience.

>and the rest is straight forward.  Ride in a car
>with a proper suspension, the comparo is really easy, you have more
>evaluation in the seat of your pants than you might give yourself credit
for.

Seat of the pants is one thing real numbers is another.

>Going wild in touring car? 

The best ideas in dampers are comming from Touring car.  Better start 
looking.

> Great for those with the bux or sponsors, given
>the prices (gave a gander too - gasp), 

I'd really like to know what you looked at since 99% of the TC dampers 
are built for the specific car.

>I don't see this coming to the mainstream for quite some time.  

Your crystal ball is little foggy then.......

>The ultimate, as always, is only a wallet
>away.  Given the level of performance B4B coil overs give, doubt many will
>hand over the ckbook for "better".

Hunh?

>Just a couple of pennies arbitraged thru the peso

I'd start saving those pennies for suspension school if I were you.

Later!


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

STEADIRIC@aol.com