Rear Sway Bar (MAC)

[Lawrence C Leung]

Running in stock class SCCA Solo2 with an A2 GTi, I was limited to just
changing the front bar. I have found that I have better turn-in with the
larger (only a 20 mm, instead of stock 15mm, which is about 50% stiffer
than stock) front bar, a fact that I attribute to the reduced roll camber
change. The reduced roll resulted in MUCH more even tread temps (yes, I
know, less telling for Auto-X than road racing, but we often ran 50-60
second courses which is approaching stable tire temps), the variance
dropped from about 14 degrees F to about 4 deg F (with btw 1.5 to 2.0 deg
negative camber and some toe out, trying not to give too much away!). In
lift throttle (turn in) situations, it was possible to work the tail, but
I'd agree on exit it will still plow without throttle modulation, which
is expected of increased front roll stiffness and FWD. However, the end
result was an improvement of times (again on a 50-60 sec go-cart course,
so that was a standard) of between 0.8 to 1.7 sec, depending on the
course configuration. Not a bad improvement for a relatively cheap
upgrade, and to give this a little more creedence, I managed to improve
my hold on our regional championship with the change. To lend a slight
bit more creedence, I managed to hold within 4% overall, my instructors
averages in my car at the McKamey Schools I've attended, some where I've
bettered them some, not. 

Where this applies to Type 89 Audis (I knew I get that in!) is, I'd be
willing to bet they roll alot too. So, try improvements one at a time.
Try bigger front bar first, then rear, then take off the front. See which
you like best. 



Old Fartz Rule! (Solo people will understand!)

LL - NY

On Tue, 16 Jan 2001 22:05:00 -0500 Patrick Austin <paanta at yahoo.com>
writes:
>Speaking from Watercooled Golf/Jetta VW experience: 
>Biggest rear bar possible with a slightly smaller front bar.  I've 
>had
>three setups:  large front, no rear.  Large rear, small front. Large 
>rear,
>large front.  The best setup was DEFINATELY the biggest front and 
>biggest
>rear bars that I could find.  This was with Shine Racing springs and
>Bilstein HD's.  
>
>Running a big front and no rear bar reduced the amount of available
>traction coming out of corners.  Turn in wasn't great, but the car 
>was
>fairly neutral initially, with understeer coming out of corners.
>
>Running a large rear bar and small front bar gave great traction 
>coming out
>of corners at autocrosses, and great turn-in, but the car would get 
>pretty
>tail-happy in lift-throttle or decreasing radius corners.  Basically, 
>it
>understeered in, and oversteered out.  It was fun, and maybe great on 
>a
>rally car, or race car with really stiff front springs (800lb or so) 
>to
>make up for the lack of a front bar, but no good on a street car.
>
>With the big front and big rear the car was very neutral.  Great 
>turn-in
>but the car didn't put power down as well coming out of corners as 
>with
>just the big rear bar.  However, while just the front bar made the car 
>plow
>out of corners, and just the big bar made the car oversteer at bad 
>moments,
>the combination of big front and big rear cancelled out their bad 
>habits.  
>
>
>At 07:44 PM 1/16/01 -0500, Alexander van Gerbig wrote:
>>    I've been yapping around with folks about a rear sway bar for my 
>car.
>>Some have said a smaller rear sway bar than the front will be the 
>best,
>>others say the exact opposite, some say it isn't needed.  I notice 
>when I
>>push the car hard I do get noticeable understeer.  I am running very 
>stiff
>>coilovers, 380 front and 340 rear with Koni Sports dialed in the 
>middle.  I
>>have a stock 22mm front sway bar, though I can upgrade to a 26 or 
>even a 28
>>if need be.  I have run into a Blau rear sway bar and there is a 
>Suspension
>>Techniques bar that will work as well.
>>
>>What would be best for a hard driver, occasional track use, and I 
>love
>>cornering quickly:
>>
>>Front: Stock 22mm  Rear: Blau 12.5mm
>>Front: Stock 22mm  Rear: Suspension T 27mm
>>Front: V6 26mm  Rear: Suspension T 27mm
>>Front: V6 26mm  Rear: Custom 22mm
>>
>>I always thought the rear bar should be smaller, but I gather this 
>isn't
>>true for FWD cars.  I noticed Ti Kan runs a 23mm bar up front and a 
>25mm
>>rear on his 4k.  Another fellow lister runs a bigger bar on his VW 
>autox
>>car.  I gather this will "neutralize" the car, but make the rear end 
>very
>>skittish.  How can I compromise and kill some understeer.  Stock bar 
>up
>>front and a small rear bar like the overpriced Blau bar?
>>
>>Thanks!
>>
>>Alexander van Gerbig -- '88 80
>>
>>The Audi  80 Pages-----------------
>>http://surf.to/the80pages.com
>>
>>North Ferrisburg, VT 05473
>>
>>
>>
>						**************
>						Patrick Austin
>						paanta at bu.edu
>						(617)782-9115
>						**************
>
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