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I'm not sure where the point of diminshing returns is on lowering on the A4 chassis.  I know with the A1 chassis, the fast FSP guys have ended up lowering it a fair amount and dealing with the roll issues with heavier springs and bigger sway bars on the front and dealing with the unloading of the inside tire with an agressive limited slip.  I'm assuming the same thing will be true with the A4's.  The general concensus seems to be to avoid going under 90* to keep the camber from getting awful and try and keep the roll center at least above gound.

 

  I've actually seen very little info on people trying to develop the A4 chassis for real performance versus the "yo, I've got a two finger gap to my dubs, what springs should I get?" crowd.  A couple of people have done well in STX with the R32 and a TT came close in DS at Nats last year, but they both use the alternate upright and have better geometry on the front end than a "normal" A4 car.  If you are serious about developing the car, you will probably have to be the trail blazer and try some stuff since most people running them are not really all that serious on the development side.

 

  Remember that these are heavy cars with a lot of nose weight, assuming adjustable ride height, I'd start a bit high and see how much travel you use in an event before seeing how low you can go.  Aluminum oil pan+too low=Exon Valdese is something to keep in mind too.

I'm only serious as to get the best bang for my $$, if i had enough i'd get these: http://www.ground-control-store.com/products/description.php/II=539/CA=4 

There's not many that's for sure, i've seen this guy lately (he is super low!):  http://forums.vwvortex.com/zerothread?id=3155418&page=1, but few else as serious.  Most just go for fun. 

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Rob P.

The new--05' Subaru WRX
The old--04' VW GTI
->the damage: http://i206.photobucket.com/albums/bb198/penderperson/WRX/pics005.jpg

VW_rob_85:

I believe that with only an inch of lowering, the center of roll is below ground, it takes another 1.5" to reach 90* on the lca's. 

So with say 450/500 lb springs, will the roll center cause the same problems on lowering as with stock rates?  The amount of roll is greatly reduced, so i would think that having a screwed up roll center has fewer consequences and would be outweighed by having a good camber curve. 

You really don't want the roll center below ground.  It screws up the car's handling and slows down transition.  Note that the roll center goes down more for a given amount of lowering than the CG does.  So the lower you go the more body roll you will have for a given spring rate.  When the roll center goes below ground level the spring rates required to keep the body roll in check would make the ride excessively stiff. 

The below gournd roll center combined with the very stiff ride, poor camber curve and roll center movement (the roll center shifts left/right as the car rolls) will really make the car hard to drive. 

VW_rob_85:

Is there a point where the center of roll moving further greatly magnifies the problem?  Say below ground?   Or is there a point where getting close to 90* improves the camber curve and thus handling, but getting closer nets little return?
 

The effect really is dependant on the specific car's geometry but as a general rule, once the roll center is below ground, lots of things start going wrong.  By then your camber curve is falling off. 

Keeping the control arms short of 90 degrees should keep the roll center above ground and the geometry in a reasonable range.

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Steve Hoelscher
#27 DP - Toyota MR2
http://www.terriehoward.com

VW_rob_85:

Ok, new problem...my control arms cannot reach 90* with complete contact to bumpstops, i doubt they will reach without them either due to coil bind.  It appears that fully compressed, i lack 1.3" to reach 90*.

For sanity sake, i measured the angle from the LCA mount to the ball joint to the camber plate bearing; this sounds logical? 

 

From what i can tell i have a few options to get closer:

 1.  Reduce stack height, i have anywhere from .3" to 1" that can come out of my stack height with custom spring perches on top.  This will lower the car and make the lca's closer to 90*.

2.  Shorten the konis...how expensive is this?  They do shorten the bottoms of the shocks correct?  This will also lower the car and bring the lca's closer to 90*, as well as increasing available shock travel.  How much shorter do i need to make them?  Can i buy a shortened version? (i'm using 8710's now)

3.  cut stock spring perches from konis and move threaded sleeves down?  (i think this will shorten the stroke even more...)   

4.  cut/remove  bumpstops, i don't think this is safe/practical/smart.

 

Appreciate the help! 

 no familiarity with the car, and you probably have already considered this, but just in case..... missing from the above is the part where you checked for tire clearance.....  at some point that becomes the limiting factor.....

 

it sounds like you are trying to get down to LCA's at 90 degrees.  you should be trying to lower the car as much as possible without running out of:

travel

ground clearance 

room for tires

favorable camber curve (checking the angles checks for this)

roll control with reasonable springs (checking the angles checks for this)

reasonably low bump steer

etc

 

#4 if you are running stock bump stops, you could switch from the "helper spring" stock bump stops to some made as actual bump stops.  I am quite happy with koni bump stops.  They have appropriate rate characteristics for SP/ST suspension, and are not nearly as temperature dependent as others I have checked out.
 

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WTB: CSP Spyder parts. What you got?

Rocwandrer:

#4 if you are running stock bump stops, you could switch from the "helper spring" stock bump stops to some made as actual bump stops.  I am quite happy with koni bump stops.  They have appropriate rate characteristics for SP/ST suspension, and are not nearly as temperature dependent as others I have checked out.
 

OK, problem solved!!  Turns out i had 1/2" of rear shock travel and this particular bump was catapulting me off the bumpstops (not for long, i cut 2" off).  Shock travel helps!

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Rob P.

The new--05' Subaru WRX
The old--04' VW GTI
->the damage: http://i206.photobucket.com/albums/bb198/penderperson/WRX/pics005.jpg