39 replies to this topic

[D. Heimgartner]

women are from Venus" of hard driving!

Greetings everyone,

I'm a neophyte of the mechanical and technical aspects of motorsports. I do understand the concepts of understeer and oversteer, however. I've experienced them both on the road and on the track (in rental karts: those little buggers that don't exceed 66kmh). By definition, understeer means that the nose of the car/kart pushes toward the outside of a turn. Oversteer, in turn, means that the tail of the car gets loose and slips toward the outside of a turn. Furthermore, I would guess that both of these conditions are a result of lack of traction on part of either the front or rear wheels, respectively.

Now what I'm curious about is which of these conditions is more detrimental to good lap times. I've heard that some F1 pilots prefer one or the other: oversteer or understeer in their setup. So what is better, what is worse. From my limited experience, it seems that oversteer is easier to control. When the tails begins to go, it seems a slight lifting of the accelerator (or even just a slight application of opposite lock) will get the car/kart back into shape. In contrast, when ever I have run a kart hard into a turn and felt the front push, it seems that I lost a lot more speed--and thus time.

[berge]

Originally posted by D. Heimgartner

Now what I'm curious about is which of these conditions is more detrimental to good lap times.

both I would think

[Ross Stonefeld]

Can any of you scientific types determine which is more impacting from a math standpoint? I know from 'feel' Understeer feels slower than Oversteer. Sliding the tail feels like you're faster, even if the mph might be lower than a car that is understeering in the same turn.

[imaginesix]

Originally posted by berge
both I would think

They cant BOTH be MORE detrimental than the other!


"Driving a car as fast as possible is all about maintaining the highest possible acceleration the appropriate direction."

Given that in both cases, lateral acceleration is about equally compromised from the optimum acheivable level, the biggest differentiator is actually longitudinal acceleration.

Understeer requires even- or reduced-throttle application to remain controllable, while oversteer requires even- or increased-throttle. Therefore oversteer will allow greater forward acceleration than understeer, therfore quicker lap times.

[Ross Stonefeld]

Yeah but you need to reduce throttle for both over and understeer. Yeah you can continue to power through some opposite lock slides, but you can also do that with understeer

[D. Heimgartner]

This afternoon, I reread the F1 mag with Schumi on the cover (the issue where all of MS's 49 wins or so are evaluated. Anyway, this issue also has an article about O. Panis, and in it, a lot of set-up/driving details are discussed. I'm not sure how valid or correct the journo's assumptions are. There's also an article about R. Schumacher, and how he turns in for corners. It seems that some drivers clearly prefer understeer or oversteer, or truly abhor one or the other.

As far as car setups are concerned (in F1), can a car be made to oversteer in slow corners and understeer in highspeed ones??? I remember a few years ago, when R. Zonta tried to take Eau Rouge at Spa-Francorchamps flat out. His rear end broke looose pretty early into the attempt. Clearly that was a case of catastrophic oversteer!!!

From what I can gather, F1 cars are supposed the exhibit neutral handling characteristics. But I could also imagine that once the limit of traction is breached, that the car will react with either over or understeer... and thus, I could imagine (but correct me if I'm wrong) that race engineers dial in either over or understeer to take over once traction limit is approached. Which of the two conditions is dialed in depends on the preference of the specific driver. From the article mentioned above, O. Panis dislikes oversteer, so I assume his car takes on understeer characteristics at the limit--and drivers take these cars to the limit most every turn, right up to the point where over or understeer occurs.

Am I anywhere close in my assumptions? If so, anyone know what drivers like what conditions...

[Wedge]

I think Zonta and for that case Villeneuve lost it because the cars were grounding out.

[berge]

Originally posted by imaginesix


They cant BOTH be MORE detrimental than the other!


"Driving a car as fast as possible is all about maintaining the highest possible acceleration the appropriate direction."

Given that in both cases, lateral acceleration is about equally compromised from the optimum acheivable level, the biggest differentiator is actually longitudinal acceleration.

Understeer requires even- or reduced-throttle application to remain controllable, while oversteer requires even- or increased-throttle. Therefore oversteer will allow greater forward acceleration than understeer, therfore quicker lap times.

I meant basically there is no lesser of two evils when talking about under/oversteer.
an absolutely neutral chassis is quickest. after that, it comes down to driver feel, ability and preferance. that's why its incorrect to just say 'one is better than the other, etc.' In the end, it comes down to the driver.

[AS110]

Oversteer can be used to set up the exit of the corner.
A late,very quick turn in,and apply power early (MH) Almost impossible to do with an understeering vehicle.

[jk]

I remember an interview on TNF where Jim Clarc discussed driving technics. He said he preferred an understeering car, because "you can made an understeering car overster, but you can't make an oversteering car understeer". I also know from GPL that most of the quick guys drive with a understeering chassis and then use their braking skill to oversteer them through the corners. Us who are not that skilled, has to use oversteering setups to be as fast. Unfortunately they are very hard to control, so i choose to drive a understeering car a few seconds a lap slower than the fast guys, but then be really consistant.

I think for just one lap, oversteer would be better if you can control it. But in a long race it will get very hard to drive fast all the time, so understeer would be better.

[mikko4500]

I'm not a racing car driver, but I'm Finnish and I've done my share of driving FWD (essentially understeering) and RWD (essentially oversteering) cars on slippery surfaces.


Yes, both will kill your speed. But in my opinion when driving a car with a tendency to oversteer (that is easily controllable by applying throttle) it's easier to find the limit at which you can drive without losing grip, whereas an understeering car is easier to handle but more difficult to push to the limit.

Basically, when driving an oversteering car to a corner, it's easier to feel when the rear end starts feeling "lighter" and turn too much and at that point it's fairly straightforward to control that with throttle and steering. It's about keeping the natural tendency to turn in check.

On the other hand, if you drive an understeering car to a corner too fast, it's the opposite. You have to ease the throttle and try to make it turn despite the natural tendency to go straight and that's what is bound to make the loss of speed (and thus time) greater.

The worst possible situation is where you drive a car that tends to first oversteer and when you ease off the throttle, oversteer. In my understanding this is what many F1 drivers refer to when they complain their car is not in "balance." It feels absolutely hideous and is a pain to drive, as if the car is going whereever it wants to, illogically, and you're trying to keep it in check.

So my bottom line is that an oversteering car needs maybe a better seat-of-pants feeling and better reactions, but it's easier to drive to the limit than an understeering car.

(Btw, in my modest opinion it's one of the reasons why Coulthard was slower than Häkkinen, Coulthard prefers an understeering car while Häkkinen likes it neutral to slightly oversteering ;)



Mikko

[Ross Stonefeld]

In terms of going off the road, whether road or race, I prefer an oversteering car. At least the spin scrubs some speed. Understeering off the road scares me.

[mikko4500]

Originally posted by AS110
Oversteer can be used to set up the exit of the corner.
A late,very quick turn in,and apply power early (MH) Almost impossible to do with an understeering vehicle.

I'd say that's the basic trick for achieving the four-wheel drift. A quick turn in helps to get the front end a bit loose and with a properly set up car you can keep it balanced by applying the right amount of throttle. To put it another way, you first make the car understeer and then oversteer it with the throttle and the end result is a balanced four-wheel drift. If the car has a tendency to understeer, then hitting the gas pedal would just make it understeer more.


Mikko

[Ross Stonefeld]

Ive seen guys correct understeer with power oversteer. So they come into an apex and pick up the throttle and it starts to plow the front end, so they instantly breath a fraction of a % then jam the throttle down and then back to where they were originally. So it goes from understeer back towards neutral. Amazing to watch and hear.

[mikko4500]

Originally posted by Ross Stonefeld
Yeah but you need to reduce throttle for both over and understeer. Yeah you can continue to power through some opposite lock slides, but you can also do that with understeer

I didn't either get something right or I don't quite agree.


If you have a basically understeering car, applying throttle will make it understeer and reducing it will either make it more neutral or oversteer, depending on the particulars.

If you have a basically oversteering car, applying throttle will make it oversteer more. Easing it off makes it more neutral.

If you go to an opposite lock slide, with an understeering car you can, naturally enough, power through it but applying throttle will either ease out the slide or just make you lose control completely, depending on that available traction and the amount of power you use.

In the same situation with an oversteering car the opposite is true and the end result is that it's easier to keep it at the "edge" of the slide. Compared to the understeering car, the idea of an "opposite lock" with the steering wheel (even though you'd never want a total opposite lock anyway) is more tangible in a way.


Mikko

[Ross Stonefeld]

Now you've confused me Im not sure where we are disagreeing

If the front end plows, you need to reduce throttle to reduce the loading on the tire. If it oversteers from power you need to reduce throttle to stop the wheelspin. If you get oversteer from like, going too fast, like turning in for the corner, you can sometimes use a *tiny* amount of throttle to squat the rear end, but its very easy to give it too much and make the oversteer worse. I think this is the basic premise behind Michael Schumacher's driving style.

[mikko4500]

Originally posted by Ross Stonefeld
Now you've confused me Im not sure where we are disagreeing

Ok, let's see if I can clarify this a bit.

If the front end plows, you need to reduce throttle to reduce the loading on the tire.

Defenitely, the basic reaction to understeering. No disagreement here.

If it oversteers from power you need to reduce throttle to stop the wheelspin. If you get oversteer from like, going too fast, like turning in for the corner, you can sometimes use a *tiny* amount of throttle to squat the rear end, but its very easy to give it too much and make the oversteer worse. I think this is the basic premise behind Michael Schumacher's driving style.

Yes, and that would establish a four-wheel drift again, more or less. I think the confusion we had was about the cause of the understeer, ie power/the speed at which you enter the corner. The way I see it, and "understeering" car always tends to understeer under throttle, and and oversteering car would do the opposite. However, any car driven to a corner faster than the conditions really allow will understeer if the throttle is 'neutral'. What happens after you apply the throttle in that situation is what defines the car as under/oversteering and in your example it would be oversteering, IMO, even though in the intial condition it understeers.

In the whole situation you get close to what Stirling Moss described to a situation where it doesn't matter if the car is understeering or oversteering, especially if you step on it before the apex.;)



Mikko

[Bex37]

Ahhh but you can also have a chassis that understeers on turn-in and oversteers on exit and visa-versa.

A car that oversteers on turn in can be diabolical to drive. You brake and try to turn-in and next thing you know you're heading sideways at the scenery. It is probably quicker than a car with turn in understeer since you can correct the oversteer with opposite lock and still maintain corner speed, but there is also a much higher chance of ending up as a part of the scenery.

A car that understeers on turn in is much slower at turn in than a car that oversteers, but turn in understeer is usually much more predictable than turn-in oversteer. If you go in too fast, you run a bit wide and when you get near mid corner you can use power oversteer to correct the understeer. The problem is that by the time you have understeered you have wiped off corner speed whilst you don't have to do this with turn-in oversteer. Most production car manufacturers err towards turn-in understeer because it is more predictable.

A car that oversteers on corner exit is usually faster than a car that understeers on exit. This is really only because you can counter the oversteer with throttle control whilst staying on the correct line. Of course, if you get too smart with the throttle the rear end can "snap-out" and you can end up embedded in the scenery.

A car that understeers on corner exit is usually slower than a car that oversteers on corner exit. When exiting a corner slightly too fast exit understeer generally means that you drift off line, which means that you have to back off the throttle or you will run wide on the exit. (Only the very brave will induce a power slide when drifting off line after the apex) Backing off the throttle is disastrous at corner exit as you this is when you most need to maintain corner speed. If you back off at corner exit it affects you adversely for the entire length of the following straight with no opportunity to change your line to pick up speed (as you could possibly do with entering the corner).

The other thing that can happen with exit understeer occurs when you are near, but not quite at, the limit of lateral adhesion at corner exit. Since you are going a little too slow at exit, you find you can accelerate harder out of the corner but you use power unecessarily fighting against the sliding of the front wheels. This detracts from acceleration out of the corner and hence affects your straight line speed for the entire next straight section. Again, this is more predictable than exit oversteer, but slower. The biggest disadvantage with this is that on some corners you actually aim to be not quite at the limit of lateral adhesion at corner exit. This is used for corners like La Source (Spa) and the Adelaide hairpin (Magny Cours) where a slow corner is followed by a long straight. In these corners it is far more important to get axial acceleration down to the ground than to have a high mid corner speed. This is because nobody can pass you mid corner and the extra few kilometres an hour you get out of the corner are carried down the entire length of the following long straight. Exit understeer has the potential to remove much of this straight line advantage.

As you can see, I appear to support the line that oversteering cars are quicker than understeering cars but they are more risky to drive. Having said that, a neutral car will always be quicker than an oversteering car. The problem is that is extremely difficult to get a car to handle nuetral in all of the following circumstances:
- on fast, slow and medium speed corners
- when fuel loads are high and when they are low
- when tyres are new and when they are worn
- when one set of tyres has a different "balance" compared to the next set
- when the weather, track temperature and/or grip level changes
- when the wind changes
The difference between a good chassis and a bad chassis is how predictably they react to all of these different things, whether the affect is extremely adverse or whether overall balance remains much the same and whether the changes are easy to correct through changes to setup.

Thats my two cents worth.

[imaginesix]

I think the answers that we are getting are far more complicated than the original question calls for. FWD/RWD, corner entry/exit, high/low speed, driver preference gna gna gna...
The basic fact is that if the rear of the car starts to break loose, it can be controlled with additional throttle application. If the front breaks traction first, then you can either ease off the throttle or live with the understeer, basically trading lateral acceleration for forwards acceleration.
So if I had to choose one or the other, and the only determinant is lap time, I would choose a car balanced towards oversteer.

[MacFan]

Carroll Smith, who knows a thing or two about winning races, has the following to say about corner exit oversteer / understeer in his book "Drive to Win":

"In order to accelerate in Phase 4* while still cornering, in Phases 2 and 3 the car must have reserve rear tire capacity. This means that every fast car will have a certain amount of Phase 1, 2 and 3 understeer.

Think about it. If you are using up all the available traction of all 4 tires in the generation of cornering force, there is nothing left to accelerate with - applying power will produce instant oversteer. Rearward load transfer and opening the line to release the car will help some, but in the case of powerful cars and slow to medium speed corners, not enough. There are ways to reduce the understeer .... trail braking, for example."

* Smith defines the 4 phases of a corner as (1) Turn-in, (2) From turn-in to apex, (3) Neutral throttle period, (4) Corner exit

[Ross Stonefeld]

However the majority of 'fast' setups are have oversteer built into them. You cant use rear tire capacity if the fronts are too loaded

[AndyM]

...Or as a car window sticker I saw not long back said said: 'Understeer is the devil, oversteer is your friend"

That sorts it for me!!

[mikko4500]

Originally posted by MacFan
* Smith defines the 4 phases of a corner as (1) Turn-in, (2) From turn-in to apex, (3) Neutral throttle period, (4) Corner exit

Hmm. My preference would be (and remember, I'm not a race driver, I'm talking about something like negotiating a corner in a slippery weather as quickly as possible) understreer in phases 1 and 2 and a tendency to oversteer in 3 and 4.

To elaborate a bit, 1 to 2 is where you actually turn in and 3 to 4 where you start easing the wheel back to centre. In 1 to 2 any amount of oversteer in that state of the car (throttle off, no braking) would mean an instant spin.

However, after the apex you start applying the throttle again to keep the speed steady and that's the time for steering the car with the throttle. If the car has a tendency to oversteer under power, you can use it a bit to help it turn and as the result you can straighten the steering wheel more and earlier. In effect, you're easing off the steering loads from the front wheels. It also means that you can start applying the throttle more earlier when closing the corner exit.

You can't do that while driving a car that has a tendency to understeer, because there you need to straighten the wheel before applying power. You have to get closer to the corner exit to do that and on the whole it's more difficult to use the throttle to help steering, in effect reducing it helps you to turn, while in an oversteering car it's the other way around.


Mikko

[MacFan]

Mikko, almost any racing car has a tendency to oversteer under power, simply because it has rear wheel drive. The only time a rear wheel drive car will not be capable of oversteering under power is when there is insufficient torque to break traction, ie a car which has an excess of grip over power. In this situation the car will understeer when the power is applied exiting a corner.

A tendency to oversteer under power can exist whether the car has an excess of grip at either the front or rear, or is neutral.

[MacFan]

Originally posted by Ross Stonefeld
However the majority of 'fast' setups are have oversteer built into them. You cant use rear tire capacity if the fronts are too loaded

The entire point that Carroll Smith is making in the quoted excerpt from his book is that the majority of fast setups have understeer built into them!

You certainly can use rear tyre capacity if the fronts are fully loaded, but there's no way you can apply power to the rears if they are already at full capacity. If you try, the result will be snap oversteer.

[Bex37]

Originally posted by MacFan
Carroll Smith, who knows a thing or two about winning races, has the following to say about corner exit oversteer / understeer in his book "Drive to Win":

"In order to accelerate in Phase 4* while still cornering, in Phases 2 and 3 the car must have reserve rear tire capacity. This means that every fast car will have a certain amount of Phase 1, 2 and 3 understeer.

Carroll Smith sounds like he is talking purely from theory to me. The fact of the matter is that it IS possible to get a fast car to enter a corner in a fast way, on the limit, without understeering and still have the ability to accelerate out of the corner without chassis oversteer.

Just because there is less traction being used at the rear during braking and mid corner it does not automatically follow that the car has to understeer at these times. For starters, there is inherently less grip available at the rear of an F1 car under braking due to weight transfer and more grip is available at the rear when accelerating for the same reason. It should be remembered that we're not talking about ladder construction chassis and beam axles here; we're talking about state of the art computer designed chassis with anti-roll bars, adjustable dampers/springs, adjustable suspension linkages and linkage pickup points, electronically controlled differentials, balasting, etc, etc. The way that the chassis handles the dynamics I mentioned above is one of the keys to a good chassis and a good setup. I certainly haven't noticed the Ferraris understeering into corners lately , and I think you'll agree that they're pretty fast (the same can't be said about the Ferrari a few years ago - but that Ferrari was slow!).

[Wolf]

Speaking of ladder chassis &c here's a quote from DSJ on the technique Moss used...

I prepared myself for certain eventualities. Imagine my surprise when we went into a sharp right-hand corner and Moss provoked (as described below) the most violent understeer by going into the corner much faster than would be reasonable and putting on a violent right hand lock. I was not actually frightened, but I remember thinking: "Crikey, what the devil does he think he's doing?" But I had no idea the road turned sharp left after the right-hand corner, though Moss obviously knew this having learnt the circuit.

Now it is quite obvious that if you provoke understeer on a car that has natural desire to oversteer you are going to get into difficulties when your artificial understeer stops, as it must when the steering is unwound at the end of a corner, and when that happens the tail of the car is going to whip round very suddenly so that the driver will need all his powers of anticipation and reflex to cope with the situation. Knowing this I thought Moss had gone mad provoking violent understeer on the 300SL at the speed we were travelling, so I just resigned myself to another accident. As the car slid through the corner and lost momentum we reached a point in the middle of the road when he straightened up the steeringand then immidiately turned it again [in the reverse direction], his movements coinciding exactly with the change of direction of the car as the artificial understeer ran out and the normal characteristic of the car took charge. At that point we were nicely placed for the left-hand bend and the car went round in delightful oversteer slide and we accelerated away up the succeeding straight. As I realised what had happened my only thought was: "Oh dear, I could never hope to drive like that, he rally is a genius."

The intersting thing is that these top drivers do all this sort of thing without any knowledge of the theory behind their movements.

[Manson]

Originally posted by Ross Stonefeld
In terms of going off the road, whether road or race, I prefer an oversteering car. At least the spin scrubs some speed. Understeering off the road scares me.

At least you can see what you're going to hit with understeer!

I prefer understeer on entry and oversteer on exit. Entry oversteer, is very difficult to control and quite scary at times. I like to throw the car into the corner with the slight understeering inducing a 4 wheel drift, then get on the throttle to pivot the car towards a late apex. Depends on the track too. The high speed tracks, I would rather have a slight understeer throughout the corner as a loose car at 100 mph is not all that fun!

Too much of each is slow but understeer is a much more stable condition. That's why almost every street car has understeer inherently built in.

[Ben]

Carrol Smith isn't talking just from theory, he was a fantastic driver in his time and has been involved in engineering some of the best drivers (Donahue, Cobb, etc) over the past few decades.

What I think this debate is suffering from is engineers understanding balance as one thing and drivers having a different view. A lecturer of mine who programmed some expert systems for Benetton said what vehicle dynamicists call understeer/oversteer is different to what the driver says when he gives feedback. This is why you can't analyse balance by looking at a data acquisition traces, it appears some of the best vehicle dynamicists have realised this (Jim Hamilton amongst others).

Ross: I think your post about a spin being better than sliding nose first off the road is great but a little out of the realms we should be talking about. Both under- and oversteer of that magnitude is slow because you go off the road.

It is pretty clear that nuetral steer, defined as zero net yawing moment about the Z-axis through the CG is impossible all the time. We need to be close to it to get the most from the car and whether the driver likes a bit of understeer or a little oversteer seems largely down to personal preference.

I suspect some drivers find understeer 'constraining' and can't get into a rhythm while others like to be able to really floor the throttle and have some understeer to soak it up. I think superspeedways are interesting because they show that above a certain speed the vast majority of drivers need some (inherently stable) understeer to ensure they stay on the course. In this range many of the corrections required by an oversteering car are simply required to be quicker than most humans can respond to.

Ben

[Ross Stonefeld]

Is there anything in the physics of an oval that makes you go to an understeer setup? Like, it seems that you can understeer all day on an oval (until you plow into the wall) but very very very rarely (montoya is one of the few exceptions) have I seen any opposite lock or even neutral steer on an oval. Ive never been able to figure out why but it seems the minute they try to correct it re-grips and shoots it straight into the wall. So maybe on an oval you could have under or over depending on how the driver likes it, but something about the banking and speed makes under the only (mainly) surviveable balance

[imaginesix]

First of all, I would hate to go off the track in oversteering (OS) mode. Any time I felt that a recovery was impossible in a car, I would purposefully steer it off the road to ensure that I was not going sideways through the grass. When that happens, it is only a question of fate as to whether or not the car hits a rut a starts to flip. RIP Greg Moore.

More to the point though, the example of high-speed setups generaly tending towards understeer (US) is true, and I think it actually supports my view that OS is a faster way around a corner than US, all else being equal. (I'm starting to hate that phrase).

The reason for the seeming universal use of US through high-speed corners is because there is so little reserve drive torque capacity to allow a driver to regain grip through increased throttle application, as can sometimes be needed. As a car nears it's terminal speed, it becomes more and more difficult to recover from OS.

If the rear end does step out, the only remaining option is to countersteer (an US moderator), and ease up on the throttle gingerly (an US aggravator), all the while hoping that grip returns quickly and controllably. If excess drive WERE available, then the driver could choose to apply a measured amount of throttle that increases the load on the rear without breaking traction. This does not necessarily require a widened arc either, but if the driver had to countersteer at least that would give him two control elements in his favor, rather than one for and one against him.

So high-speed US is a safety issue, it is not intended to improve speed. The less US a driver is comfortable with at high speed, the faster he will corner.

[mikko4500]

Originally posted by MacFan
Mikko, almost any racing car has a tendency to oversteer under power, simply because it has rear wheel drive. The only time a rear wheel drive car will not be capable of oversteering under power is when there is insufficient torque to break traction, ie a car which has an excess of grip over power. In this situation the car will understeer when the power is applied exiting a corner.

A tendency to oversteer under power can exist whether the car has an excess of grip at either the front or rear, or is neutral.

Yes, any RWD racing car tends to oversteer under power in slow corners when there's no wing downforce and there's not enough traction for the amount of power applied. This is power-induced oversteer.

A similar racing car with a certain wing setup can have a tendency to understeer in fast corners. Anti-roll bars, string stiffness, load changes and such also have an effect. This is wing/chassis-induced oversteer. This can be demostrated in practice by driving a RWD car on an icy road, then adding a sack of full gravel to the boot and driving the same road again, trying not to lose traction at any time. It makes a difference because the weight distribution, load changes on springs and such are different.


Mikko

[Ben]

Originally posted by imaginesix
More to the point though, the example of high-speed setups generaly tending towards understeer (US) is true, and I think it actually supports my view that OS is a faster way around a corner than US, all else being equal. (I'm starting to hate that phrase).

The fastest setup is not the one that is theoretically fastest for the car, it's the one that allows the particular driver to go quickest in that car. So a mildly understeering superspeedway setup IS quicker than an OS setup in this situation because it allows the driver to keep the thing on the road.

I still think it depends on driver preference because both US and OS both scrub off speed by creating larger slip angles than are necessery.

Ben

[Colin]

Not being a race-car driver, I have a question. Most of this discussion has centered on turn-in occuring after all the braking has happened on the straight. But what will happen when trail-braking into a corner? I can rationalize it two ways:

- Weight transfer forward off of the rear wheels reduces grip at the rear, inducing oversteer

- Weight transfer forward onto the front wheels reduces traction at the front, inducing understeer

I suppose it depends on exactly how much of the grip is being used at each end of the car. The weight transfer onto the front wheels will induce understeer at smaller steering angles than it otherwise would occur, so perhaps it depends on the radius of the bend. Looking at the rear, if there is surplus grip at the rear it may not matter that some grip is being taken away. It's hard for me to visualize which of the scenarios would occur (or would be more common) in a real car on the track. Can anyone shed light?

Also, this question was asked earlier in the thread:

As far as car setups are concerned (in F1), can a car be made to oversteer in slow corners and understeer in highspeed ones???

With wings, yes. If the aerodynamic balance it set up so that the center of pressure (CP) is behind the CG (i.e. more rear wing than front wing), then as downforce is added a greater proportion will be added to the rear tire, inducing more understeer as you go faster. This is also a more stable situation than putting the CP in front of the CG (think of a dart thrown backwards). I believe the standard setup is to put the CP slightly behind the CG; putting the CP back too far would induce too much of a change in the car's low speed and high speed behavior, and it also induces too much of a stabilizing yaw moment acting to prevent the car from turning.

[Ross Stonefeld]

Trail braking is really going to make this complex

How you even come off the brake pedal is going to affect car balance. The car wont rebound as quickly as you can release the brakes so you can affect balance by whether you snap off the pedal or slowly release.

[imaginesix]

Originally posted by Ben
The fastest setup is not the one that is theoretically fastest for the car, it's the one that allows the particular driver to go quickest in that car.

Ben

Absolutely. I am talking purely on a theoretical basis here.

There are plenty of good reasons to want to induce US on purpose, it's just that none of them have anything to do with increasing cornering speeds (directly), it is only ever about stability.

I think the difficulty with the question is that we are trying to identify the 'lesser of two evils' from what necessarily has to be a non-optimised suspension setup. OS and US can be caused by maybe hundreds of different setup/driving changes, each one having it's own consequences.

It is difficult enough to try to guess the effects of suspension changes when it is assumed that everything else is optimised, to try to do so when there is an unidentified flaw in the setup is impossible. That is why I think we can only revert to the basics of handling theory to provide an answer.

[100cc]

Originally posted by Bex37
Ahhh but you can also have a chassis that understeers on turn-in and oversteers on exit and visa-versa.

very true. Often drivers think that their car has too much oversteer, and try to fix it, but in fact it might have initial understeer, which then turns into oversteer.

On the braking, letting off the brake too suddenly(at least in a kart), will through it sideways, but the driver will usually know what he did wrong in this case.

[Powersteer]

Understeer and how do we control it is by lifting the throttle or touching the brake pedal so meaning longitudal control only which means going faster or slower. Oversteer can be control with the same means but added with a steering wheel too which says that oversteer can be controlled without the means of longitudal changes but lateral too. So lateral forces changes without changing speed which will be quicker theoreticly. Direction can be maintained but car angle will be different. One thing though, an oversteering vehicle would surely benefit when controlling tyre slip angles because the whole car is telling you the slip angle where as a steering wheel is to vunerable towards forces for understeer. As you can see many racing drivers gerking the wheel(defenately even the best who are so smooth with the rear end) so slip angle control is out of the question there for understeer.



Car angle is another thing. I would have to say oversteer is positive car angle and understeer is negative because understeer would mean the car doesnt want to go round the corner while oversteer means it wants to go round the bend too badly this is yaw angle. Oversteer defenately has an advantage in car preparation into a corner like what rally drivers do before a bend. This is also good to get a feel of the car. Talking about angles this is one of the very formula that invented the four wheel steering mechanism which can only be duplicated through oversteer on a two wheel steering system.



So finally what set up do you want? One is defenately a clown when setting up a car for wet weather in understeer mode let alone snow or ice so i am assuming the road condition is dry and grippy. The question of this forum forgot one part, neautral sliding, also known as drifting. Hardest to set up because even the current top F1 teams have some problem as the drivers are still whining. This would be MY choice because with this set up, in dry, i can choose oversteer,drift or even understeer. I'll take a sharp corner with the tail out, drift in a nice speed corner and go flat out with none or slight understeer in a high speed bend.BTW Senna mensioned in his book on race driving that understeer slows the car down less than oversteer while many drivers opt for it on faster corners.


Think in another thread it is mension about sliding and not sliding, WRC difference in principal compared to F1. WRC wants to complete a corner quicker while swinging round a bend, F1 wants to do it faster because the WRC cars have so much longitudinal grip while the F1 has so much lateral. Think it also comes down to ratio. The bigger the wheels and downforce, the further the gap between slip capability and stick.

[Amadeus]

Originally posted by Wolf
...so I just resigned myself to another accident...

[Wolf]

Amadeus- I don't think it was laughing matter for either of them...;) Practicing for the event Moss had an accident in which he hit Italian Army truck full of live ammo.
Noone got hurt, but that gives the term to resign myself to another accident whole new perspective.