Wow.. I thought A1 setups were pretty much "a known" after all these years.....
So ...
I haven't seen anyone mention rear camber. Stand the tire up so it will rotate in roll. Super high pressure is something I would only accept as an option in an AX car where you had no other legal options to tune. On a road course thats just silly. silly=dangerous. You may wind up with blistered tires or a car that is extremely unstable under braking. If you find you MUST run 60 psi to rotate your setup wrong or your car is really bent.
A good set of shocks as another tuning aid. Something with a rebound adjustment that will help rear rotation. (KW, Koni, PSS9 etc)
A front swaybar does nothing positive on a FWD car. If you wind up with a car/driver that likes (or needs) very soft front springs then and only then can you go with a stock or lighter than stock front bar to limit roll. It still will reduce inside front tire grip and induce wheel spin coming out of corners. A good LSD will help.
>> I also run a locked front diff, so my setup is different. I run about a 22mm front bar, with a 19mm rear bar, with 500 lbs front springs and 350 lbs rear.
Tim what happens on your car when you remove the front bar?
>> It makes for a fast car, but it is VERY unforgiving with 400lb springs in the back.
Eddie, how much camber and what kind of toe do you run back there? Do you have all solid rear bushings?
>> The bunny goes all dog leg in nearly stock form as it is doesn't it? I would think super stiff springs would make that worse?
No a stiff spring will limit roll more and reduce the amount of "3 wheelin". Now having said that there are obvious negatives to a high spring rate ... reduced grip for example. I think you are thinking about the rear axle beam stiffness. If you stiffen the beam with a big sway bar it will lift a wheel immediately. But the benefits of a stiff rear outweigh the loss of traction on the VERY lightly loaded inside rear tire.
>> I am going to try out 700# fronts and 400# rears
James, try swapping your springs front to rear... as long as the rear camber an toe are under control, you'll go faster. You might want to come down on that rear spring rate from 700 to 550 though with a big rear bar.
>> books where they say run just enough spring rate to keep the bodywork off the tires, and use bar for the rest
That advice is a bit more applicable to a RWD setup where the rears are in need of traction coming off a corner. But that is also OLD info... modern shocks allow us to control a much heavier spring which will allow you to have car that will RESPOND quickly to driver inputs and be fast on transitions. If we raced ovals it would be different. Now having said that it is still true that a lighter spring will have a theoretically higher potential for grip than a stiffer one... but the car is raced under non laboratory conditions.
>> to try and keep my inside front wheel on the ground.
It's really not possible on the beam axle cars. You're better off accepting that fact and going for maximum corning speed and drivability than trying to keep all 4 on the ground.
>> I borrowed a buddies CRX set up real stiff on a track day, and I could barely drive it!
A Honda rear suspension (correct me if I'm wrong) has an inboard mounted spring with a motion ration somewhat other than 1:1. therefore a 1000# spring on the rear of a Honda is NOT a 1000# at the wheel like it would be on a VW. The rear sway bar has a largely different effect on the rear of a Honda as well. So you cant just pull a setup off any FWD car and have it work on a beam axle VW.
>> In the MK3 we decided to go with an 800# front with a 550# rear. hopefully with this setup I will not have to add a Rear bar to get the rotation I am looking for.
It's all about "balance". You need to think of the car as a whole and not just what each end wants independently. You may find this works for you but I would argue that removing the front bar, or leaving it there and going with a stiffer rear bar will give you the proper balance you are looking for without going too a real high rear rate. With 800/550 I'm thinking you'll have quite a bit of understeer and poor front grip in slow/tight corners.
You may wind up compensating with toe out up front and rear more camber up front...but both those things are reducing tire grip to true and obtain the effect. Try swapping your front and rear springs.
>> The handling books say to use a bar. The books dont race very tall VW race cars with struts (edit: and a beam axle)
Exactly :026:
>> Try the welded diff with the big # front and some adjust ment for the rear.
What did you find with a welded diff and no front bar?
>> Part of the problem w/ the front control arms angled up is the front roll center going under ground
Here is one area where a stiff front spring can help. (by virtually eliminating roll) but then you have push and grip issues. VWs can NOT be lowered like a Ferrari.. PERIOD. Drive it high and proud or get a Honda
>> 1) what pressures are you running (cold/hot) in the front and rears.
>> 3) please chime in with your spring rates, and front/rear sway bar rates
1. Follow the tire manuf. suggestions for their hot pressure target. Adjust your cold pressure so that you reach their hot pressure target noting that sometimes on a light VW the rear will never make it to optimum temp on days below 100* track temps. Once you find that cold pressure, you should work on the suspension setup as that will change your temps. Keep an eye on them and adjust up or down as needed. Then after you've got the kinematics all sorted you can use tire pressure tweaking as a
fine tune for flaky sets of tires, rain, hot cold days, odd track surfaces etc. Do not use pressure to cure a massive push etc. Something else is wrong in that case.
3. A lot of what has been said here depends on the driver. There are guys out there who think they are 'bad fast' but if you put them in a car with a loose rear end they will freak out and say it's a scary undrivable mess!
For them (and take an honest look at your own skills here) they need a car with more understeer to be comfortable. They will always be a bit slower than a loose car since they will not be able to pick up the throttle as soon... which btw is THE name of the game. But their confidence will be higher and they will enjoy their race car more.
For those that CAN handle a loose FWD car. Your goal is to become Pobst/Kleinubing ... Counter-steering while ENTERING the corners is not unheard of in a FWD car.... watch some in-car video of Pierre at Mosport in the RSX for a good example. Picking up the throttle should "set" the car by transferring weight rearward which vertically loads the rear tires causing them to grip and then
by mid corner you should be at WOT.
Watch Greg's hand position here at mid corner:
http://www.youtube.com/watch?v=H_pgUUhIjAw
Notice how he's often bringing his hands back to near center as the rear is leading the front? Well setup.
Also notice how he just blows by all the VWs on the start... and finally Zaslow in the boot. What's up with that Dave?!
TRAIL BRAKING is generally very bad in a FWD unless you are on the "defense line". I say a defense line because braking early squaring off the corner and accelerating early will leave you open to attack from behind. Trail braking overloads the front tires. Again the driver is usually one of the biggest influences on this understeer. Trail braking is a recipe for understeer. Did I mention I dont like trailbraking in a FWD?
The main problem on corner exit is how to kill the understeer. For those with 100hp it's not a big deal. However on our Corrado (and any VW in damp conditions) it is an issue. Early rotation is key.
For those with adjustable shocks here is what I see working in VWs...Generally I run quite a bit of front & rear rebound to try to keep the car flat on turn in. The rebound is also to stop the front from tending to lift under acceleration after the transition from brake to accelerator... Front bump is kept soft to maximize grip and prevent hop on rough surfaces, rear bump can be set higher. Generally rebound needs to be at least twice the bump setting and depends a lot on the driver and how bumpy or smooth the track is.
The above is from 30 years of experience in putting my nose in where is doesn't belong and picking the brains of those who were fast even before I started driving. The Hackers, Pate Brothers, ICY Racing, Oag, Schwartzott, Pobst, VW Motorsport, and probably a 100 other VW racer's info and data have filtered through my notebooks over the years... When I was working in IMSA back in the late 80s early 90s I was fortunate enough to talk regularly to the pros when the Scirocco 16v, Golf GTI and Corrado G60 were being raced professionally. In almost every case... those who went fastest were softer in front, stiffer in rear and ran little to no bar up front and lots of bar in the rear. Today's setups are not much different. Our cars and cars like those Christian Miller's World Challenge Jetta are playing with similar setups... we're going bigger in the rear bar while lowering spring rates... shocks and shock DATA are keys here.
Remember it's about WHEEL RATE not spring rate. So throw your Honda setups out and remember that the rear bar directly affect your rear spring rate. IOW a 500#/400# setup with a big rear bar means this car is much stiffer in the rear than front contrary to what the spring rates alone show.
I could go on and on about contact patch, camber gain in roll, camber thrust, RC axis wrt to mass centroid, scrub, offset, shock valving relative to wheel motion, shock frequency histograms (very useful tool BTW) ackerman, compromises ... yadda yadda yadda.. but you guys need something to do in between events.
Yes, It will be very loose in the rear until warm but also you have to do a lot to the rear to stop the beam from twisting, bending, and the bushings from slopping around. If you dont it will be a mess back there. You've seen my posts here about the rear beam anti-toe linkage? That and spherical bearings and things that are also not legal in IT are required to get it "nailed" back there.
.
