[V8] Track F/R discussion

Tue Apr 17 11:07:14 EDT 2007

This is my last post on the subject. Too many of you hear what you want to hear, rather that what I'm typing. 

Now Dave, what does your wifes Odyssey have to do with a lowerd v8? the last line I posted was " On a lowered car, which is more susceptible to bump steer? the one that rides smooth (or semi smooth) race track, or the one that rides down your typical public road or highway?"

Please read "lowerd" and "more susceptible".  I didnt ask if was more imortant or that it matters more on a track verses  the street. Symply that you will experiance it more on the street than the track with a lowerd car. But I guess you didn't get that. Al

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  ----- Original Message ----- 
  From: Coleman, David 
  To: QSHIPQ at aol.com ; allanvega at adelphia.net ; ingo.rautenberg at gmail.com ; jward.v8 at gmail.com 
  Cc: v8 at audifans.com 
  Sent: Tuesday, April 17, 2007 10:40 AM
  Subject: RE: [V8] Track F/R discussion

  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)

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    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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