34 replies to this topic

[Monza Bambino]

Hi guys,i`ve a question about understeer,it`s a two part one...

1/ is understeer irrelevent at low speed,that is...if a corner has a top speed of about 200kph,and the Maclaren takes it at 160kph,is there any detectable understeer,would at 160kph,the Maclaren be in anyway at a disadvantage to the Ferrari at 160kph.

2/What is the exact problem with understeer,is it simply lower corner speeds,or lower corner speeds and excess tyre wear.

Interested in your thoughts.

[Real Estate Queen]

I don't know very much about driving techniques, but I will give it a shot anyway.
Please note first that corners don't have top speeds. Cars do have a limiting speed when going through a corner, and that would be the speed, beyond which the car would be no longer able to remain on the road as intended, due to the loss of grip at the tire/road interface, unless corrective action is taken.
This long introduction is only to say that natural understeer (or oversteer for that matter) will only happen beyond that limit speed, not before. So I think it could be said that no difference should be noticed among any cars able to handle that speed, be it a go-cart or a 200 ton truck.
This is of course based all on theoretical analysis and on the laws of physics. I am saying this because the answers to the second question are more open for discussion, and I don't have the answer, but would like to hear the opinions of people who know about this in detail. This I say because some conditions could be induced into a car which could actually make it go faster through a curve complex (i.e. not only the curve itself, but also including the parts before and after the curve).
As for tire wear I have heard that, under normal circumstances, more grip means more wear, but then again, I don't know.

GO JPM GO !!!!!!!!!!!

[Peter Perfect]

I'm not an expert but...

..I'm still going to try to answer the questions.


1) If one car has understeer and another oversteer and they take the same corner at the same speed then it takes the same amount of time (velocity/distance=time). BUT, the understeering car may suffer from excessive wear to the front tyres (the front tyres are basically being scrubbed) while the oversteering car may suffer from excessive wear to the rear tyres (the driver tries to the power down but the rear tyres slip).

2) Trying to make an understeering car go quickly through the corners is tricky. The steering can be turned all the way, but the radius of the corner turned will be dependent on the speed of the car.(try to make the car go faster and it'll want to go straight on)
Trying to coner quickly in an oversteering car is really more in the drivers hands (literally). The car will want to turn into the corner, and can be corrected by the driver with the steering.

So, I think, an understeering car is more dependent on its setup to go quickly, while an oversteering car can be (when driven by a good driver) pushed closer to the edge of the cars absolute performance.

[Monza Bambino]

Peter and R E Q,thanks..i was trying to understand Malaysia,where RS basically outdrove Mika,in the wet and variable conditions, if understeer is not a relevent factor at less than the maximum corner speed,how can we understand the result?

[forgey]

The way I understand it to work is that an understeering car will always understeer, the higher the speed the worse the understeer.

Therefore if a car understeers it will understeer more at 200mph than at 160mph. The amount that it understeers at the lower speed though may not be noticeable enough to make a difference though.

Note that I have no real racing experience to speak of.

forgey

[Ben]

Originally posted by Real Estate Queen
Please note first that corners don't have top speeds. Cars do have a limiting speed when going through a corner, and that would be the speed, beyond which the car would be no longer able to remain on the road as intended, due to the loss of grip at the tire/road interface, unless corrective action is taken.

This long introduction is only to say that natural understeer (or oversteer for that matter) will only happen beyond that limit speed, not before. So I think it could be said that no difference should be noticed among any cars able to handle that speed, be it a go-cart or a 200 ton truck.

First point is correct. The second point is in my opinion wrong.

Understeer simply means that the car steers a path with a greater radius than that required by the geometric ackerman steer angle (this has nothing to do with 'ackerman' steering geometry they are two different things). Two simple ways of characterising this are that the front slip angles need to increase at a greater rate than the rears to maintain a path and the result of this is that more lock must be applied to turn.

Oversteer, understeer, and nuetral handling can all occur through the speed range depending on the setup but obviously for a given setup the speed will influence them (aerodynamic balance).

The reference to a limiting speed makes me think of the critical speed, which is a vehicle dynamics term for the point at which the yaw response curve diverges, but there is no critical speed for an understeering car so I suspect that wasn't what REQ was refering to.

Forgey is right a US car will just keep requiring more steering input the higher the speed, or more accuratly the higher the lateral acceleration. This is represented by the understeer gradient in degrees of extra steering angle / g of lateral acceleration.

Monza Bambino: could you clarify the 'result' you're trying to interpret? I'm not entirely sure how you can generalise about understeer because MS was quicker than MH in Malaysia?

Ben

[Real Estate Queen]

Ben:

I think that speed has everything to do with it, since it affects the car's dynamics. I understand aerodynamics play an important role in the racing car world, but for the sake of simplicity, and to better understand what causes the car to behave in a particular way, we should ignore them here. I used the term limiting speed so that we could relate more directly to the reading of the speed meter in the car, but the all important component is the lateral acceleration of the car in the direction of the radius of the curve, and in this particular case, the forces the front wheels are subjected to at this speed, which in the end elicit the extra input necessary for the corrective action. If what I have just said makes sense, and borrowing from your explanation, the speed at which the yaw response curve diverges does dictate the car's behavior. Below this speed no particular condition should be noticed.
Mybe I am wrong, or maybe it is just a problem of semantics (i.e. I say US or no US, and you and forgey say some US, more US, a lot of US).
By the way, what are your views on the tire wear question. From many comments I have heard and also read here on an old thread about TC, the answer is not as straightforward as it looks.

GO JPM GO!!!!!

[jetsetjim]

I think one of the biggest problems here is that people are trying to generalise the terms understeer and oversteer in a single sense.

What people have to recognise is that there are various forms of each.. dependant on whether the car is at Turn-in, Apex, or Exit of any given corner.

Ben describes the dynamics of understeer precisely. The causes of understeer are numerous though..

High speed US suggests that the aero balance on the car is not ideal, with either too little front wing, or too much rear. This gets worse the higher the speed. This is true for TI, MC and EX US

Turn-in US:

Excessive speed being carried into the corner.. 99% of the time, this is a driver error.

Slow to mid speed US is usually a mechanical issue. If the ride heights are not optimised, it can affect the weight transfer from rear to front under braking and turn-in, putting less weight to the front than is needed, resulting in a lack of grip. Other effects such as Castor angle, toe settings, etc can effect the turn-in. Another area which can cause TI US is the Differential.. incorrect settings on Drive and Braking can cause the car to "push" into a corner, again causing understeer. If you look even further into the problem, you get down to the basics of suspension geometry, and the effect of steering inputs. All can cause US..

Mid-Corner US:

Again, the Diff can cause this, depending on the settings. Other possibilities include areas such as damping.. the bump and rebound settings can give a vast amount of car control.

Exit US:

This can be down to 2 things essentially.... the geometry of the car, and the damping. If the front of the car has very little rebound damping, to hold it down, the front comes up very quickly under acceleretion, reducing the contact patch of the wheel, therefore taking grip away. with regrads to geometry.. it is not unusual for cars to be designed with an amount of "pro-squat", which is used to aid traction under acceleration.

Obviously there are a whole load of explanations for OS, and similar logic can be applied to determine the causes.

[Monza Bambino]

Ben

Monza Bambino: could you clarify the 'result' you're trying to interpret? I'm not entirely sure how you can generalise about understeer because MS was quicker than MH in Malaysia?

I`ve been hearing all year how the Maclaren`s have a understeer bias,and as such,DC will perform better than Mika.

If on a dry track,detrimental understeer occurs only near the limit,the limit is 1/2 a kph before the car breaks traction...how is Mika at a disadvantage in the wet,when the limit is not approached.
Ie dry track corner speed 180kph,wet track corner speed 150kph.

If the understeer characteristics are neutralized by the wet,is it fair to say on that day,RS outdrove Mika in the wet,with near identical cars?

[unrepentant lurker]

Originally posted by Monza Bambino

If on a dry track,detrimental understeer occurs only near the limit,the limit is 1/2 a kph before the car breaks traction...how is Mika at a disadvantage in the wet,when the limit is not approached.
Ie dry track corner speed 180kph,wet track corner speed 150kph.

If the understeer characteristics are neutralized by the wet,is it fair to say on that day,RS outdrove Mika in the wet,with near identical cars?

Well, if the track is wet, the corner speed is no longer 180kph, its now 150kph. Do you think they are no longer driving at the limit just because its raining?

I don't know enough to say how a car is effected in the wet - I imagine it has to do with setup, etc. As to RS vs MH, I believe the racing line was dry at the end of the race, everybody on slicks. However, since RS finished ahead of MH, then yes he did outdrive him.

[Monza Bambino]

URL

Well, if the track is wet, the corner speed is no longer 180kph, its now 150kph. Do you think they are no longer driving at the limit just because its raining?

Of course they`re driving at the traction limit for the weather...but if understeer is only critical at the maximum dry corner speed,is that the Mac a understeerer,of no limiting consequence at lower speeds,as occurs in the wet.

[Real Estate Queen]

Understeer is a function of the traction limit. If the track is wet, you are simply moving the threshold to a lower value. Dry track conditions no longer apply. Imagine the extreme condition of having the same cars racing on an ice track (i.e. very little grip), and you will clearly see the difference.

GO JPM GO !!!!!!!!!!

[Monza Bambino]

Originally posted by Real Estate Queen
Understeer is a function of the traction limit. If the track is wet, you are simply moving the threshold to a lower value. Dry track conditions no longer apply. Imagine the extreme condition of having the same cars racing on an ice track (i.e. very little grip), and you will clearly see the difference.

GO JPM GO !!!!!!!!!!

I`m only guessing here,but i don`t think that`s true....the amount of understeer must be at it`s highest disadvantage at the upper limit of dry track traction.

At the upper limit of wet track traction you will spin due to the lack of grip on track,but the centrifugal forces are much less,150kph vs 200kph.

My question is,is it fair to say in the wet,understeer is minimal,and driver skill and set up are the major factors.?

[unrepentant lurker]

I don't understand why you think understeer can only occur (or is at its worst) in the dry. See the Queens post.

Spinning in the wet is usually a result of too much power too soon or locking up the rears under braking. Locking up the rears would seem to be a brake balance (ie setup) issue. Too much power too soon is a driver skill problem (or nowadays a bad software engineer:rolleyes: ). Also, I think most drivers setup their car for the dry for a race where mixed conditions is expected. I *think* this would lead to overstear in the wet. MS seems to be an exception.

Certainly understeer is achievable in wet conditions.

[Janzen]

If you have a balance problem with a car, then the same problem will appear whatever the surface. And I would even dare to say that it will be even more difficult to drive a car in the wet that has handling problems.

The better the traction on the contact patch the more time you have to correct, is that correct there was discussions about this and the new tires, the drivers saying that the loss of traction was more sudden.

[Monza Bambino]

Ok,thanks guys.

[Ben]

The problem with McLaren earlier in the season was that they had a lack of front downforce which was causing less lateral force to be generated by the front tyres (less load = larger slip angles = understeer) this is simplistic but was the explanation used by all the commentators and the media at the time.

Understeer does not simply go from zero to a particular value at a given speed, I think that is simplistic to the point of being very unhelpful to understanding the concept.

Jetsim's post is a great little summary of the causes of understeer (by no means comprehensive but you would need a whole book to cover everything:) )

I totally agree about most of the comments on wet conditions. If the global friction coefficient is lower the forces are lower but understeer/oversteer/nuetral steer are about the sum of yaw moments about the centre of mass. If all the forces are reduced by the same amount the resultant yaw will be the same.

Ben

[Real Estate Queen]

Thanks for clarifying Ben.

GO JPM GO !!!!!!!

[Ross Stonefeld]

Understeer should be the same at all speeds (generally speaking) in a non-winged car shouldnt it? Understeer is based on tire loading so if I overload the fronts I can get as severe understeer in a hairpin as I do in a 5th gear kink

[Monza Bambino]

Ben

I totally agree about most of the comments on wet conditions. If the global friction coefficient is lower the forces are lower but understeer/oversteer/nuetral steer are about the sum of yaw moments about the centre of mass. If all the forces are reduced by the same amount the resultant yaw will be the same.

But isn`t aero downforce reduced,particularly when you start dry,and have rain during the race, the corner speeds are reduced, i realize they can dial in some wing downforce.

Maybe my question is silly as i don`t know the total difference between a wet and dry set up.

If we agree that the Mac and Ferrari have,for agruments sake neutral handling characteristics on a dry track at 80% maximum corner speed,what comes into play at maximum corner speed,more wind resistance,if so...isn`t that wind resistance reduced at 150kph vs 200kph.

IOW,if critical amounts of understeer are prevelant at maximum dry track corner speed,and wind resistance and front wing efficiency are the major culprits,why would the mac be at a disadvantge by understeer at slower corners speeds albeit with less surface grip,and less surface grip being a common factor for all cars?.

[Ben]

Can we stop talking about a critical speed for understeer please? It doesn't exist.

My previous post does explain why the McLarens could suffer from understeer despite the lower speed.

Ben

[Wolf]

Ross- I don't think so. For example, I drive a car that is basically an oversteerer, but in sone turns (mildly sharpish) understeer can occur. And for another matter, in sharp turns she behaves as an understeerer but when the traction limit is exceeded she breaks out with the rear end. Hardly a surprise that many drivers get caught off guard with that car.;) Short wheelbase, drum brakes all around and RWD only add to perils for bad drivers.

But, regarding original question, I think it is not the problem of understeer itself that bothers people in racing (when they speak of it like McLaren earlier this year) but it occuring at lower speeds than it should. But the matter can be more complex as one can see from their differential blocking device that got banned. IIRC, it was meant to decrease exiting understeer caused by differential under hard acceleration.

[Yelnats]

Understeer is more limiting than oversteer because the rear tire of an F1 car supports a much higher percentage of the cars weight than the front so it is more critical that the rear operate at it's limit. If the rears don't operate at their cornering limit, a larger proportion of the cars potential cornering traction is wasted than if the same situation occurs at the front. So the idea is to set up the car so the rear's grip is maximized and then tune the fronts till their grip matches the rear. If the fronts cannot achieve enough grip to reach this situation then the grip levels must be adjusted via roll stiffness changes at either end of the car.

From the drivers point of view, if the front plows into the corner (understeer) and the rears never reach their limit, the driver is helpless to turn the car further as his steering is essentially disabled. But if the rears drift out too far (oversteer) the car still can be steered so driver will back off the steering a bit and negotiate the corner (if a snap spin doesn't intevene first).

[Ben]

Good points.

Just to clarify further. An understeering car is defined as stable because it has a tendency to want to stay understeering. The terminally understeering car has saturated the available control moment and the driver can do little about it (other than steer out and add some throttle).

This is different from linear understeer which we have been talking to up to now. Yelnats talks about performance at the limit.

Oversteer is unstable because small changes in the cars position will create large outputs (i.e. they want to spin). Large amounts of control moment are available from the front tyres but little stabilising moment is available from the rear tyres.

This demonstrates the important point that the front tyres supply control while the rears are responsibility for stability. The trade-off here is that a stable car doesn't want to change direction quickly while a responsive car has a greater tendency to swap ends.

Ben

[Keith Young]

In one of my articles I have a paragraph on McLarens weakness in slow sectors. David did complain of oversteer but I hope this can help.

USGP Tech Report

[KenC]

Originally posted by Monza Bambino
Hi guys,i`ve a question about understeer,it`s a two part one...

1/ is understeer irrelevent at low speed,that is...if a corner has a top speed of about 200kph,and the Maclaren takes it at 160kph,is there any detectable understeer,would at 160kph,the Maclaren be in anyway at a disadvantage to the Ferrari at 160kph.

2/What is the exact problem with understeer,is it simply lower corner speeds,or lower corner speeds and excess tyre wear.

Interested in your thoughts.

Amazing how well behaved Mr. Bombastic can be when he wants to get an answer. If you look closely at his posts, you will see that he has a hypothesis, that Ralf outdrove Mika, and he wants you guys to give him the proof. As soon as someone confirms what he already believes, then he will return to the other message board to slag Mika and praise Ralf. What a user!

As for your questions:
1) If the McLaren has inherent understeer at 200kph, it might have even more understeer at 160kph. Think about it. The chassis has its own inherent balance, neutral, oversteer, understeer, dependent upon setup and corner type, etc. Any inherent imbalance might be offset by aero tweaks. In this case, perhaps more front wing to help cure this understeer, in your hypothetical corner.

Now, imagine a wet track, where cornering speeds are lower. That would mean, the chassis would be less aero dependent for cornering grip, and more mechanical grip dependent. If the aero settings become less important, due to lower speeds, then any inherent chassis bias becomes more prevalent. If this bias is understeer, then it will be even more understeering, at a slower speed.

So, going slower thru a corner does not make understeer "irrevelant", based upon your hypothetical situation.

2) What's the prob with understeer? It delays the driver's ability to put the power down on corner exit.

As for Ralf, he is known as a driver who is quite good with an understeering car.

[Monza Bambino]

Amazing how well behaved Mr. Bombastic can be when he wants to get an answer. If you look closely at his posts, you will see that he has a hypothesis, that Ralf outdrove Mika, and he wants you guys to give him the proof. As soon as someone confirms what he already believes, then he will return to the other message board to slag Mika and praise Ralf. What a user!

I think what`s more amazing is how i`ve internally wounded you.

Unfortunately little Ken,i`m a Mika fan.

I was trying to establish the ability of Ralf compared to JPM...that is,if Ralf can outdrive Mika in the wet...where does this leave JPM,who i don`t rate as a WDC threat next yr.

Little ken,i took the technical forum seriously,why can`t you,is it that dreaded internal wounding,i`ve given you a whopping boy.

[Real Estate Queen]

Please leave the personal arguments for the RC.

As for Monza's question regarding JPM, and from a technical point of view (this is the technical forum, isn't it?), I would like to bring to your attention an interview done recently with JPM's father in which he admits that the biggest problem his son has had this year in setting up the Williams car, is the fact that it has too much understeer for his driving style. He also admits that he doesn't really know how come Ralf is so good at driving such an understeering car.
I think that since the more knowledgeable people in this forum have already answered the question from the technical point of view, we should continue this discussion at the Soap Opera Forum (i.e. RC).

GO JPM GO !!!!!!!!!!!!!!!!!!!!

[Ali_G]

A few questions.

1. I went Karting there the other day for the first time in a long while. The nature of the circuit was that there are 2 very fast corners and a number of hairpin like slow corners.

This is what I found. Going through the fast corners, the car was well balenced. I was just abuout on the edge and if anything I was experiencing a little oversteer.
Yet when I got to the slow corners, I was experiencing masses if understeer. Horrible horrible. Not exciting at all.

Is there anyways to alter my driving style to less the effect of understeer through slow corners.

As it is, I like to brake in a stright line and gently turn into the corner. Also for the hairpins I tend to try to apex very late to masimise the speed down the next straight.

Any ideas.

Plus would stiffenign the front suspension help ? (I wouldn't be leeft near the Kart setting anyway though)

Niall

[KenC]

Originally posted by Monza Bambino


I think what`s more amazing is how i`ve internally wounded you.

Unfortunately little Ken,i`m a Mika fan.

I was trying to establish the ability of Ralf compared to JPM...that is,if Ralf can outdrive Mika in the wet...where does this leave JPM,who i don`t rate as a WDC threat next yr.

Little ken,i took the technical forum seriously,why can`t you,is it that dreaded internal wounding,i`ve given you a whopping boy.

Like I said, Mr. Bombastic is here with an answer, looking for a question. I think it only fair to the other members of this forum for them to know what you are up to. You are not asking a tech question, but are looking for some arguments that you can take out of context to throw around the other board. That's pretty lame, because I'm sure you would never give the proper credit where it is due.

As for taking the forum seriously, I did answer your questions, did I not? What exactly did you add to this tech discussion, other than asking your loaded question?

As for "whopping"s, didn't you know harassment is means for banishment? Good luck with your Juan obsession, maybe you'll find some evidence to support your theories, somewhere!

[Wolf]

Niall, I am not sure whether I should make this suggestion, since it may get You in a lot of trouble...;) Enter a corner giving it more steering than needed, and when expiriencing understeer try giving it more throttle than required (to induce wheelspin loosing grip on rear wheels as well). If You get all things straight You'll end up in a nice four wheel drift... If not- You're on Your own, I didn't make this suggestion. I did it few times on the road and would advize caution, but it sure does make Your blood flow faster.

[oldtimer]

A non-technical contribution. In 1958, Mike Hawthorn used to set up his Ferrari for understeering drifts, whilst Peter Collins preferred to set up his car for oversteering drifts. Shots from the British GP at Silverstone show this well.

So, my point is that driver preference is part of the equation.

[confucius]

I've read that DC copes better with understeer than Mika because of the way he drives, that is, carrying more speed into an earlier apex. Apparently Schuey and Ralf also apex earlier and may be why they deal better with understeer. In regards to the technical reason for this, I'm not sure.

[MacFan]

Niall - that is the way a kart should be set up! If you brake into the slow corners as you're turning in, the extra weight transfer will reduce the understeer, resulting in a nicely balanced 4 wheel drift if you're any good, and a quick trip to the scene of the accident if you're not.

General comments about the thread topic:

-All racing vehicles must have some corner exit understeer - how could you put the power down if you were right on the limit of the rear tyres coming out of the corner? You would have violent snap oversteer, and would have to wait until the car was virtually straight before waving a toe in the general direction of the throttle = not quick

-It is extremely difficult to achieve this exit understeer without at least some mid-corner understeer, which the driver will have to deal with if he wants to be quick.

-IMO a lot of confusion about understeer and oversteer is caused by different driving styles - driver 1 will claim a car has severe oversteer, while driver 2 will complain about understeer, in the same car with the same settings (Olivier Panis claimed in an interview earlier this year that he couldn't drive DC's McLaren because it was too pointy, but Hakkinen's settings were fine for him, despite Hakkinen preferring oversteer and DC preferring understeer). IMO the difference is in the amount of trail braking different drivers will "naturally" use into slow and medium speed corners.

[MacFan]

Originally posted by confucius
I've read that DC copes better with understeer than Mika because of the way he drives, that is, carrying more speed into an earlier apex. Apparently Schuey and Ralf also apex earlier and may be why they deal better with understeer. In regards to the technical reason for this, I'm not sure.

Mika needs a car that will react very quickly to steering inputs, as he takes such a late apex. DC and Ralf are still braking as they turn in, so they can still make an understeering or slow-responding car rotate on its axis and turn in to the corner (the weight transfer from the trail braking effectively increases front grip and reduces rear grip). Michael normally drives this way, but he has the extremely rare ability to adapt his driving style to suit the car.