Oversteer/Understeer

We're doing the final tweaking of p 4/5 C Stradale and basically have huge rear grip and when the car starts to let go very slight understeer.

We're running race ABS/TC/Huge downforce (2800lb) and road Pirelli tires (Pretty soft)

My other cars seem to lose the rear a touch but this one in planted.

Our testers/engineers feel this is safest.

I'll test her next week.

Any thoughts/preferences?

I don't run ultra hard but will track her a bit.

 

From a racing perspective, I like a little understeer at the limit on turn-in and oversteer on exit. Getting comfortable with aero grip is counterintuitive, and the understeer is a good indicator and desirable. It will slow the turn-in a touch, but it's a reasonable trade off.

CW

 

Thanks!

I've never really pushed in a high downforce car and will need some time to understand how it works.

 

why the Pirellis? can you run something else?

anyway if this is primarily a street car, a little understeer is probably a good move. can you do adjustments (sway bars/dampers) easily to change the car for the track?

 

Because they are the best size for road use where we're running a different size wheel/tire to
reduce turning radius and raise ride height a touch. We worked with Pirelli a lot and they suggested this tire and it seems to work very well on the car.

The car is very easy to adjust but I'm looking for an overall setup that will work for me as this one is a LOT faster than me.

It pulls 2.8G's in medium speed turns.

On the race set up we ran bigger F than R. On the road we're not.

 

Our road wheels and tires.
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I should also say that, in the middle of the turn, I also prefer a little bit of oversteer. Easy to manage with the throttle. There's plenty of theories about loose being fast, and it can bite you, but it's not hard to modulate as necessary.

CW

 

I'm just wondering if more of an R-comp would be better for a car generating that level of downforce, even on the street.

bigger tires on the front in what way...treadwidth? wheel diameter? tire diameter? all of the above?

and I agree with CW, slight understeer in, slight oversteer middle through exit is ideal.

 

Treadwidth/wider wheel

 

was the KERS (or whatever hybrid system you had) driving the fronts? if so, that makes sense.

 

Just curious because I have never driven an aero car, how it is counterintuitive? Is it like golf where you have to hit down for the ball to go up?

Dale

 

No RWD. A lot of newer race cars are "square".

We were slight over square.

At the Ring our drivers told me they definetely didn't want to oversteer.

 

P1 cars are square. I'm not aware of any (other) RWD/AWD race cars that are over square.

 

Something like that.

With conventional mechanical grip, when you get understeer, it means you've over-driven the front tires, and you'll have push. So, when you back a little out of it, your grip returns.

When you experience push with an aero car, you get more grip when you go faster (the counterintuitive aspect, as opposed to backing out of it), as the downforce is building on the front splitter. So, if you've got your wheel turned over, and you're still going straight, the answer is in more throttle, which also produces faster exit speeds. This works up to the point the tires can't take the lateral grip. But, until then, it's great!

CW

 

Sounds perfect!

 

Too many points on that circuit where the car becomes unloaded AND requires a direction change... I can sympathize with that!

 

What are you expecting with street tires? Did you change other aspects for street tires, eg. roll stiffness?

 

We have several engineers working on the car and the head of our Team is an ex Goodyear tire tester who developed the F40 tire. They changed a number of thing but overall think the car is very planted and safe. Without ballast and air restriction we've got a lot of power and our weight is good (About 600 petrol/50 KERS/2700lb)

He was very pleased and said on the skid pad he couldn't lose the rear. We're testing at a manufacturer's test track/center so we're going through it step by step. Stop and go. Traffic. Hills, flat sections bumps,short course/long course.

Tomorrow we're checking everything and then next week we go back for high speed testing.
After they think all is good I'll test for a day and then she'll be ready to come home.

We have lap times we did there full race spec. so we'll have something to compare to.

 

[ame=http://www.youtube.com/watch?v=BTY9tQKdRjg]P4/5 Competizione test at Portimao GP - YouTube[/ame]


This is surprisingly accurate.

2011 Version pre KERS and Shark Fin

 

Okay, okay, I can dig it. So how does trail braking work on an aero car? I'm thinking T2 at Laguna, which, as you probably know, is a double apex. So you go in deeper than you ordinarly would, right? But how do you rotate the car? That is, what happens when you lift? Is it a sudden pop? Do you need trailing throttle just to settle the car?

Damn, the first SOB who did this musta had balls.

Dale

 

You have to trust in the physics and the aerodynamicist.

As for rotating a car, this is what practice sessions are for. There are a couple of tricks. For tighter, lower-speed corners, I'd brake-steer it, get it pointed in the right direction and get on the gas. Done right, you never lose momentum or aero grip. In faster corners, more speed. At Laguna, I'd be thinking more speed.

I've driven Laguna Seca, in Formula cars a LONG time ago (same track configuration, though), and I don't remember it as being particularly problematic (downhill, straight-line approach, pretty flat through the corner, wide entry and exit and set-up for T3 is moving to driver's left after the exit). The thing I'd concentrate on is getting my line right. Turn the wheel once, get the car on the right line, don't unsettle the suspension and then play with the throttle a little to see what works best. A double apex really isn't anything more than a big, single radius turn if you do it right.

Trailbraking isn't particularly special, either. The most difficult aspect is when you release the pedal and are transitioning the car to power. That's when the car is the most "unsettled", and when you're going to have the least grip. So, it's at this point that you want to drive like you're on your tiptoes and make adjustments gently. You can get a little oversteer at this point, and once it snaps around, you're just a passenger. I've found that the quicker I am on the throttle after trailbraking, the faster the grip returns and the sooner the rear re-plants itself.

CW

 

Thanks, that makes sense. I dunno if it is true or not, but one thing I was told about the design for COTA was that the purpose of T12/T13/T14/T15 conga line was force the F1 cars to slow down to the point where the aero no longer works.

Dale

 

One of the biggest problems with F1 (and any other series in which aero grip is present) is passing. Processionals are boring.

To get close enough to the car in front of you to make a pass, though, means you have to get into its dirty air, which, of course, disrupts your own aero, and drops you back. Thus, in an effort to promote passing (which has been a complaint for a while of Tilke-designed tracks), slower speed corners can help create more passing opportunities.

CW

 

Is it going to still have the roll cage from the video when its a street car? I dont think that would be safe

 

That's a sim. The street version will be modified.