[V8] Track F/R discussion

Tue Apr 17 10:40:49 EDT 2007

Excellent mediating points Scott -- I too am following with interest,
and don't see a pissing match -- just the airing of opinions to uncover
the facts.  I am try to find the commonality between the full-race track
setup on my inherently disadvantaged yet track record setting,
championship-winning fwd Mk1 VW touring car, and a mildly tuned street
V8.   "Flipping front tie rods"?  Hmmm.  I'd like a before/after session
for that mod alone to convince me, with all the slop in other areas,
that this would make a notable difference.  Not doubting, just need more
info.. Jack's contribution has been worth my study, even if I'm not sure
it applies to non-rwd chassis 100%.

My scca racer has a widened front track, and the front coil-overs set to
lower the front end enough so that, viewed from the front, the control
arms rest a few mms past parallel to the track surface (i.e. ever so
slightly inclined toward the hub away from the pickup point).  Very
heavy front springs, no front sway bar.  -2.5 to -3.25 deg camber.   Out
back, less heavy 400# springs, fat sway bar, and about an inch lower
than the front, with zero (-0-) deg camber.    Corner-weighting sets
actual corners a tad catty-wampus in relation to one another, but
overall this setup is the result of 3 seasons of much trial and error.
If I want better still, my next move is to take 100# out of the front
springs.   Point is -- it works well, and I love it on track, but it'd
be extremely impaired/undriveable on the highway..

....  The V8, on the other hand, is a different car in nearly every
respect, and I'm not chauffeuring bank CEOs on a daily basis.   But I do
drive it on the highway, sometimes for exended periods of time with a
passenger or two.  So I want crisp, *predictable* handling that will
respond to an on-track mentality, but not require enough concentration
to miss a roadsign or a witty observation from the passenger area...  An
RS6 provides to me about the ultimate feel, but to achieve that would
require changing every single part on my car to that from an RS6...
8-)

With koni/H&Rs installed, and the hunt on for a rear bar,  I'm about
there... would like to hear real-world experience in adding a turn of
stiffness to the front struts, but they're rebound-only, no?   And as
Scott describes it, the sucky front suspension geometry is familiar to
me and can be worked around.  I like the appearance of the V8 lowered,
and would even like to see my front dropped another 1/2".  Hey, the DTMs
were lower in front than the rear...maybe it's time to hack a coil off
my H&Rs!   And not to be flippant, but Scott, your Pobst-approved track
car has no competition (H&R/etc) springs?  Maybe Randy was just being
congenial??    ;-)

This whole discussion came about from optimal wheel/tire setup, which is
highly subjective.  I want to be able to rotate the tires without
breaking beads, so all four wheels and tires must be equal.   And I
would first and foremost add wheel width by way of offset rather than
spacer, but am not opposed picking up some 10mm and 15mm spacers, if for
no other reason, to use as tuning tools.

Sorry for the epic novel -- if you made it this far, you're not working
hard enough.

-DaveC.

PS:  bump steer matters far more on a race track  (I've yet to see an
aftermarket modification to tune the bumpsteer on the wife's odyssey)

________________________________

	From: QSHIPQ at aol.com [mailto:QSHIPQ at aol.com] 
	Sent: Tuesday, April 17, 2007 9:12 AM
	To: allanvega at adelphia.net; ingo.rautenberg at gmail.com;
jward.v8 at gmail.com
	Cc: v8 at audifans.com; Coleman, David
	Subject: Re: [V8] Track F/R discussion

	Watching this thread with some interest, and I'm pretty sure
Jack has a firmer handle on this than Al may give credit.  IME, type 44
(and most early quattros for that matter) take to *raising* chassis
height a lot better than lowering chassis height - a tribute to the
quattro being a rally car first.  On the type 44 (5ktq) race car I set
up, I found that the best compromise in the front was to drop ~.5inches,
and then address all the other ways to optimize the chassis.  I have
since dropped it a bit more, but have had to totally rebuild the
suspension setup, from bar rate to spring rate.  For wide track
modifications, I see the best benefit on a type 44 by dropping this
.5in, and adding as much track as you can.  For better handling, I'd go
after wider tires front than rear (adjusting tire size for equal rolling
diameter).   Since Al hasn't indicated what the setup is for, this may
be extreme.  However, what I will say is that a triangulated front
swaybar/control arm just plain sucks.  Compared to the artistically
crafted rear multilink suspension in a type 44, it's a sin to put the
front together like that.

	As such, accept the fact that the front isn't optimal, and
optimize the rest of the car.  Spacers are one of the best
modifications, and the v8 wheel wells can accomodate the widest
additional track without mods other than the RS6.  Al, I looked at
swapping ball joints, but I really don't see the benefit.  I would
encourage you to really watch chassis loading on a alignment rack before
you go too far here.  IME, you can see the slop in that front suspension
which (to me anyway) dictates that you go after a lot of other avenue
before you drop and tweek arcs.  

	In my personal chassis tuning experience my highest 'n'  is in
the 44 and C4 .  Mostly from having to work with a lot of the nasty
effects on handling a triangulated swaybar does to the suspension under
load.  I know from simply a geometry standpoint, beyond .5in drop on a
type 44, better suspension dynamics under load can be found elsewhere in
that chassis.  One of the first and best is wider track front.  I also
don't find wheel bearing loads to be excessive with spacers, that IME is
usually more associated with drop, not width.

	Backing off my pulpit a bit, my first question is 'what you
doing with the car?'  If you want better handling, there are a lot of
stock ride height options that have better potential handling without
the compromises.  If you are doing a full out race car (btdt), weight
and chassis stiffening is one of the higher priorities.  When I read H&R
and swapping steering tie rods, I think wow, I didn't even do that on
the race car yet?  And when Randy Pobst drove the beast with me shotgun,
there is no doubt that whatever I did passed good muster ( we did have a
rear brake issue, which he blamed on the caliper, I blamed on trying to
ditch that SQ behind him)

	When I read widening front track, and tire sizing the
front/rear, I think you guys are onto something good.  Al, I guess I'm
not really clear on what your objective is.  My cumulative experience on
type 44 and C4 chassis can be summed, don't be too quick to drop, you
spend a lot of time fixing something that audi already compromised on
when they shot the end of the front bar thru the control arm.

	HTH and my .02

	Scott Justusson

	In a message dated 4/16/2007 9:21:03 P.M. Central Standard Time,
allanvega at adelphia.net writes:

		Sorry Jack, but Ingo never stated that spacers affected
how the suspension works. His exact quote was
		"Careful there, buddy! When you're adding spacers,
you're effectively
		changing the suspension geometry, even if only
slightly."

		to which my response was "......Simply widening track
doesn't affect anything 
		but the load on the wheel bearings....."

		Perhaps I should have said widening the trac has no
"ill" effect on the suspension,cept for the wheel bearings. But since we
were already talking about ill effects, I guess I felt everyone knew
what I meant. My bad. No where did I state that widening the trac had no
affect on the handling.  I mean come on man, why would I have purchased
them if they didn't improve the handling. The H&R race springs with a
spring rate of 350lbs front and 300lbs rear should negate any spring
rate loss do to the lever action of the spacers. As for flipping the tie
rods, well you got me there. It was something I didn't put a whole lot
of thought into, but it did seem logical. I guess i have a few options.
1 Fill tapered hole with weld and re-taper from the bottom (hard way) or
2. bore out the taper, and use none tapered tie rods from later Audi's
found  here---->  

http://www.ecodetuning.com/shop/cart.php?m=product_detail&p=102 

		Don't know if this will work, but I will let the list
know if it doesn't. Al

		  ----- Original Message ----- 
		  From: J123fs at aol.com 
		  To: allanvega at adelphia.net ; ingo.rautenberg at gmail.com
; jward.v8 at gmail.com 
		  Cc: v8 at audifans.com ; David.Coleman at blackrock.com 
		  Sent: Monday, April 16, 2007 9:03 PM
		  Subject: Re: [V8] Track F/R

		  I'm not sure I agree Ingo.  Simply widening track
doesn't affect anything 5/2007 6:43:10 P.
		  but the load on the wheel bearings. Lowering a car
would (and does) have an 
		  effect on the front control arm, steering arm,and
axle's. I have been 

		  Sorry Al,
		  Ingo is correct. Widing your track DOES affect how the
suspension works. 
		  You are correct, it does not effect the static
geometry, but as I have an effect on the roll center of the car......and
to say it does not effect the handling on the car is factually
incorrect. 
		  It also makes the front springs effective rate lower
by a fair bit, as you are making the lever arm acting on the struts and
springs longer. This too also effects handling.
		  I had an interesting off list exchange about this
recently, and in the middle of the MASSIVE Northeaster we where getting
here on Cape Ann ran the numbers on SusProg3D, while watching it gust to
over 70 mph on the anemometer. 
		  On our cars changing the track 25 mm lowers the roll
center 4%. Dropping the car an inch or so does about the same thing- but
you then tempt the pothole gods. This can and does effect the
suspension. I could not accurately figure out the spring rate change as
it was way too S#$%^tty to venture outside to measure the control arm-
(VW rabbit/Porsche 944/944tT control arm - same length and articulation
angles already in my database) but on a car already in the database
changing the track 25 mm changes the effective spring rate by 7+%. Not
chickenfeed numbers wise. You COULD argue that it's not apples to
apples, but the Audi C-Arm IS longer, so I bet the numbers are even
higher.
		  I would be worried about the CV's- I have seen every
brand of car racing with lowered springs decrease the life of NEW CV's
by 75%+. The issue isn't the static position, but as the suspension goes
through it's range of motion and it runs out of length. Most guys who
change their geometry, change the length of the axles also. You HAVE to.
		  I would like too see the tie rod end inverted- this
makes a LOT of sense when it comes to bumpsteer on an lowered car with
such a highly mounted steering rack, but will it work?
		  I just replaced a split braided brake line (yes it
happens, thankfully I was going slow) and spent a good deal of time
planning my subframe upgrade along with tie rod ends, ect while
replacing the hose, and I'm not too sure you could reverse the taper on
the strut arm without welding and re-machining the thing to accept the
tie rod end upside down. Do you know something I do not?
		  Jack

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