Understeer ... the good, the bad & the Technical

[venkyhere]

I believe the prime benefit of flexi front wings is not 'reduced drag'. Reduced drag in a straight line at high speed, is a secondary benefit that. The prime benefit, according to me is in high speed corners. The FW flexes, reduce the front downforce, shifts the center of pressure rearwards in the car "automatically" and introduces understeer. That's what the driver wants in a long radius high speed corner. In slower corners, no FW flex, high downforce in the nose => helps rotate the car faster. This 'dynamic balance change to suit different types of corners' is the real benefit of a flexi FW.

[venkyhere]

I believe the prime benefit of flexi front wings is not 'reduced drag'. Reduced drag in a straight line at high speed, is a secondary benefit that. The prime benefit, according to me is in high speed corners. The FW flexes, reduce the front downforce, shifts the center of pressure rearwards in the car "automatically" and introduces understeer. That's what the driver wants in a long radius high speed corner. In slower corners, no FW flex, high downforce in the nose => helps rotate the car faster. This 'dynamic balance change to suit different types of corners' is the real benefit of a flexi FW.

There is no scenario where any driver would want to induce understeer mid corner, except to counteract snap oversteer. Understeer is especially hurtful on a long radius corner that you take as an example here.

The benefit of flexing wings comes from the fact that you can run with a lot more load at the front, without a drag penalty which would otherwise nullify the advantages in (certain) corners with losses on the straights.

Probably the word 'understeer' was the culprit. And I didn't mean that the car would suddenly become understeery mid-corner, after entering with neutral balance. I mean 'introduce a bit of understeer by removing a bit of DF from front => shift the balance more towards rear' - didn't mean the car has understeer w.r.t a neutrally balanced car. No.
For slow and medium corners, a fast F1 car has to be sharp on it's nose, especially for small radius corners, because you want the car to 'rotate' quickly.
For fast long radious corners, if the car has the same front wing level, due to the extreme speed, the front DF will grow to become too much, so much that snap oversteer is highly likely. So if there is a way to 'on the fly' reduce the front wing level, the front DF wont grow to monstrous levels so as to make the car highly sensitive to yaw (a slight noise input from driver's hand muscles, a slight gust of wind etc). The total front DF would still be higher than the slow and medium corners, when the front wing 'reduces' ; but the 'balance' of the car would shift rearwards, reducing the sensitivity of the car to snap. The 'balance shift' would start even before corner entry as the entry is happening at high speed. So no 'mid-corner' change as you mentioned.

[Andi76]

I believe the prime benefit of flexi front wings is not 'reduced drag'. Reduced drag in a straight line at high speed, is a secondary benefit that. The prime benefit, according to me is in high speed corners. The FW flexes, reduce the front downforce, shifts the center of pressure rearwards in the car "automatically" and introduces understeer. That's what the driver wants in a long radius high speed corner. In slower corners, no FW flex, high downforce in the nose => helps rotate the car faster. This 'dynamic balance change to suit different types of corners' is the real benefit of a flexi FW.

There is no scenario where any driver would want to induce understeer mid corner, except to counteract snap oversteer. Understeer is especially hurtful on a long radius corner that you take as an example here.

The benefit of flexing wings comes from the fact that you can run with a lot more load at the front, without a drag penalty which would otherwise nullify the advantages in (certain) corners with losses on the straights.

What you say is not quite true. Of course a driver doesn't like extreme understeer. But in fast corners, an understeering balance is definitely preferred, as is a slightly oversteering balance in slow corners. It is therefore quite correct that the main aim of the flexible wings is to "adjust" the aerodynamic balance accordingly. In slow corners you want more "front bite" and a little more downforce at the front, while in fast corners the aerodynamic balance should move slightly towards the rear. No driver wants a car that constantly threatens to break out at the rear at 300 km/h.

[Farnborough]

As a destination for the interesting discussion going on in Ferrari SF24 thread, hopefully to encourage continued debate and examinatory contribution.

I think it should be most specifically about this trait in high speed, high torque/throttle application, avoiding the intricacies of low corner speed dynamics for clarity of topic.

[Farnborough]

I too felt it interesting discussion and worthy of forum input.

Hopefully the content can be moved to here viewtopic.php?t=31911 and continue.

[Greg Locock]

What definition of understeer are you using?

[Tommy Cookers]

,,, I think it should be most specifically about this trait in high speed, high torque/throttle application, avoiding the intricacies of low corner speed dynamics for clarity of topic.

Maurice Olley would have agreed with that

in slow corners accelerations in yaw are large - so dynamic 'understeer' significantly leads steady state steer behaviour

[Farnborough]

What definition of understeer are you using?

Thought I'd exclude slow discussion (as it reduces the need to involve long comparison) but see what is understood by other observers of F1 in regard to how that would be interpreted.

Blunt view would be exaggerated "armful" of lock with vehicle travelling straight on, nuance would need far far more refinement of description and better resolution, to align with what the drivers are doing.

I know what I think and have experienced, that in kart, rally, road car, motorcycle both on and off road there's manifestation of it and driving with it to good and poor effect.

Technically, it could be defined by the wheel spindle trajectory being directed in tighter radius than that which the wheel is following, to ultimately bring the vehicle path below tbat requested.

But in high torque high speed, with rear lateral movement giving yaw to chassis, then with fronts effectively running straight (steering wheel not turned) but gradually moving to wider radius overall .... is that under or over steer .... or the two technically balanced ? Thinking in track terms of 2nd 1/3 Parabolica at Monza to give example.

What do you think, and how would that be described ?

[Sevach]

No one wants understeer they want stable, and what feels stable to some drivers will feel like understeer for others.

I've read a comparison between Hamilton and Button during their Mclaren years, by one of their chief technicians, with how you have to optimize the car for the whole lap, the team could put more front in the car for Hamilton because he would be able to deal with the rear at it's critical points, no complaints whatsover with a setup Button would call undriveable.
And then in tighter corners where a car that rotates faster is beneficial Hamilton would profit.

[AR3-GP]

Some drivers confuse understeer for pushing a car faster than the downforce it produces will allow.

If you drive at 200mph and attempt to turn for the first chicane at Monza, you will "understeer"....This is not an "understeer" problem. This is simply going too fast for the corner. There is a reason that the cars have brakes.

[dialtone]

Some drivers confuse understeer for pushing a car faster than the downforce it produces will allow.

If you drive at 200mph and attempt to turn for the first chicane at Monza, you will "understeer"....This is not an "understeer" problem. This is simply going too fast for the corner. There is a reason that the cars have brakes.

That happens because they see telemetry where they lose 0.1s in the first corner and try to do it faster. That’s a fine way to experience understeer

[Greg Locock]

As I understand it Mark Donohue developed a good enough, objective, definition of understeer that was testable and meaningful. Drive around a skidpan at constant radius. Accelerate to a higher speed. Did you have to apply more steering wheel angle (SWA) (understeer) or wind some off (oversteer). Rinse and repeat for all operating conditions. Then look at SWA changes under dynamic application of throttle. In the end you'll have a matrix of understeer vs speed vs radius vs throttle ramp rate.

There are other definitions, that one seems at once usable and easy to understand. If you just throw words around without defining them then any discussion will devolve into hair splitting and misdirection.

[Tommy Cookers]

... Did you have to apply more steering wheel angle (SWA) (understeer) or wind some off (oversteer) ? ....

with a proper car driven properly both less SWA or more SWA will make the car run wide of the circle
that is 4-wheel drift
but (post-WW2) lazy people started to call it drift

btw
driver skill isn't necessarily shown in 'tail-happiness'
eg if a car is designed eg for 30/70 weight distribution that's because more power can be used in & exiting corners
(as another poster has said) Mr Prost and Mr Alonso won lots driving that way (& won me some dosh) ....
some (eg Mr Alonso early footage) slap on lots of SWA seeming to provoke understeer and then wait for the car to turn-in
once an excitable ex-racer car salesman demonstrating a front-engined Porsche showed me that

[Greg Locock]

"with a proper car driven properly both less SWA or more SWA will make the car run wide of the circle
that is 4-wheel drift" That's at the friction limit, as Stirling Moss more or less said, a properly balanced car at the limit is on a trajectory.

OK, so for the understeer experts. You have two identical cars. Now make the front tires a bit stickier, and the rears less sticky. Call this car O. The other is called U.

Now do a step steer maneuver. with the same steering wheel input. Which car's yaw velocity increases most quickly?

If you can't answer that then you are better off talking about armfuls. Any bicycle model is good enough for this. The answer is one reason why understeer is a good thing.

[venkyhere]

OK, so for the understeer experts. You have two identical cars. Now make the front tires a bit stickier, and the rears less sticky. Call this car O. The other is called U.

Now do a step steer maneuver. with the same steering wheel input. Which car's yaw velocity increases most quickly?

Even though I'm no expert (just a background in high school physics) , my answer would be :
"O".
And the notion in my head is that for slow, low radius corners, a car needs a high yaw rate (to minimize rotation duration) and for fast, large radius corners, a car needs a lower yaw rate (rotation duration is not critical, dulling the sensitivity to 'noise inputs' to the front wheels becomes critical, since the high speed makes the angular momentum of each wheel super high).
Whether ackerman or anti-ackerman (F1) steering, the 'delta' in angular momentum (for a particular SWA) across the front wheels, grows spectacularly as the speed increases, and it's beneficial to stability, to keep the amount of slip suffered by both front wheels more or less even in that case. Completely opposite for slow and tight corners.