Alan Herod

I was the guilty tech inspector(and former Chief Instructor). There is some missing information here. LandJet is new to this car and to track driving. This car is a '95 993 with '95 993 suspension geometry. I was concerned that a 0/0 Green student with a high horsepower car (supercharged 993) would be driving tail first more often then not. If anything I would want this car to plow a little. The HPDC is an event we do as a prerequisite to DE. I noticed the settings which were contrary to everything I have seen for a 993 driver. I consulted with two other very experienced 993 drivers. After the shop changed the sway bar settings, I talked to LandJet at the HPDC and he relayed that the car seemed to have a more floaty feeling when cruising on the highway in a straight line which I can not attribute to a sway bar settings alone. I relayed that something else must have been changed when the shop readjusted the sway bar settings to a more neutral setting. We were expecting to see LandJet at Mid Ohio next week; but it looks like Shenandoah is his next target event.

kurt M

Standard advice I have heard from the pros is to set both ends in the middle and REMOVE "bar" from the too tight end until you are happy. There is much more to all this. Things such as spring rate, the track corners or driving style you are tuning for and the like. As you increase the spring rate to total body weight you tend to need less sway bar rate. Race cars have big fat springs or T bars but a harsh ride. Street cars use smaller springs to make for a softer ride. Less spring rate for agiven body weight makes for more body roll and the need for roll compensation via the sway bars.

A perfect suspension setup would not need sway bars at all. They connect the independent wheels together making them less independent. What one wheel is "seeing" affects the other. In the simplest sense sway bars are there to keep the car body from leaning side to side not tie the wheels together. The only way they can reduce roll is to use the other wheel to lean back against so this is why they are set up this way. What they do is good, how they do it is not so good. As was said you want to have as little sway bar as you can to keep the wheels independent. They are a necessary evil so to speak in conventional suspensions.

Often times someone will bolt on big fat sway bars and drive around the block and thing "Man the car is rock solid!" What has happened is the big sway bars reduce roll and when driving far from the traction limits the car will feel real good. Problem is when you get the car near the traction limits it gets unpredictable or has too much under or oversteer as the wheels are locked together and there is less overal traction.

How or why does this work you ask? Warning! Gross Generalisations to follow.
When you have too much rear bar the rear wheels are being kept in the same line and as the body wants to roll the inside wheel will be pulled up from the pavement ether fully or just have less pressure pushing it down. This makes you loose traction. The front wheels are better able to conform to the road as the body rolls and do not loose as much traction. So as the car turns it looses more rear traction than front and the back end will want to slide before the front does.
Switch from too much rear bar to too much front bar and the opposite happens you turn the wheel the car leans in and the front wheels loose traction and understeer. (Push in NASCAR, Slide in standard non car guy English)


So, too much at ether end will make that end have less traction at that end. Too much overall will reduce traction overall. The goal is to use as little at both ends as is needed to keep the car body from leaning and changing the suspension geometry too much. The goal overal is to have all 4 wheels stay in full contact with the road and be able to move up and down as the road does.

171mph

Also keep in mind that neither springs, dampers nor roll bars will change the lateral load transferred to the outer suspension when cornering. This is ONLY modified through the car's center of gravity (lower = less lateral transfer) and track width (wider = less lateral transfer). I recommend Skip Barber book "Go Faster" for details.

Tspringer

Here is my opinion which is worth exactly what you have paid for it.....

Forget about what you think is going to be faster or slower. As Carroll Smith said about racecar setup, the first goal is to get the driver comfortable and confident (CC) . If the driver is not CC, then nothing else really matters and this goes 10x for drivers who are relatively new or inexperienced in a racecar or track car.

Plenty has been said about the theory and general dynamics of what bar settings will yield what results. On top of this keep in mind (again in theory) that SOFTER = FASTER. But... too soft and you get weight transfer that yields sacrificed control and thus slower. So its all a balancing act and before you can really get results from this balancing act you need to get CC!

IF you are not pushing the car to the point where you know you are fighting either oversteer or understeer and you can describe exactly what handling characteristics you are experiencing and exactly how they are impacting your lap times, then I would suggest your not to the CC point. A driver who is not CC will not be getting all there is to get from a particular setup and thus the objective of any changes should focus on getting the driver CC.

I would suggest setting the front bar stiffer but toward the middle of the setup range and the rear bar toward the middle but softer in the adjustment range. Then forget about them and go drive the car. Post back if/when you have specific negative handling characteristics you want to correct. In the meantime, build confidence in yourself and the car as it is.

My little '69 911S track car has adjustable SRP bars front and rear. I have been tracking this car for 5 years now and have been playing with the bars. I want to be able to get on the power earlier in the slower corners and I want the car to turn in better in the really fast corners. Thats a neat trick to balance! At Road Atlanta last weekend I removed the rear bar totally. Well, I could get on the power earlier but the inside front tire was lifting badly and the higher speed understeer was worse on corner entry. Worst of all.... the car no longer rotated on throttle modulation as I like it to do. I was no longer comfortable nor confident. Would that be an ultimately faster setup? Well, Jack Lewis races his 2.0 HSR car with no rear bar and he is blindingly quick. But for me, I hated it. So for me it was definitely slower.

I put the rear bar back on and set it 3 holes stiffer than my "normal" setting. This I liked. The car rotated more on throttle application and I am comfortable balancing this with the steering. So the rear end got looser.... and I got happier. comfortable and confident, lap times improved.

The point of this ramble is that ultimately you will setup the car to how YOU like it and you wont really know what this is until your pushing the car to the limit such that while being confident and comfortable you can describe exactly what handling trait you wish to correct.



Terry

Land Jet

Good point!