Coping with understeer predicamen
Discussion
Oh my god I have to correct a few things here before some of you die 
through overcomplicating a very simple action.
Understeer is caused by one of two things in a drivers actions. Too much speed or incorrect throttle balance timing.
Understeer on exit comes from impatient throttle input to balancing the gas too soon or too high an entry speed pushing you past the apex.
Talk of higher gears is irrelivant because once in the corner you have what you have and you deal with it relevant to the 2 above scenarios.
To counter any of the two scenarios look where your going and use logic. If you can't your cars too fast for you.
through overcomplicating a very simple action. Understeer is caused by one of two things in a drivers actions. Too much speed or incorrect throttle balance timing.
Understeer on exit comes from impatient throttle input to balancing the gas too soon or too high an entry speed pushing you past the apex.
Talk of higher gears is irrelivant because once in the corner you have what you have and you deal with it relevant to the 2 above scenarios.
To counter any of the two scenarios look where your going and use logic. If you can't your cars too fast for you.
Simon Mason said:
Oh my god I have to correct a few things here before some of you die
Understeer is caused by one of two things in a drivers actions. Too much speed or incorrect throttle balance timing.
Understeer on exit comes from impatient throttle input to balancing the gas too soon or too high an entry speed pushing you past the apex.
Talk of higher gears is irrelivant because once in the corner you have what you have and you deal with it relevant to the 2 above scenarios.
To counter any of the two scenarios look where your going and use logic. If you can't your cars too fast for you.
are you saying then that understeer is purely driver induced and that there's really no such thing as an inherently understeery car, just drivers too impatient on the throttle? ie you should always wait until at the straight before applying the throttle?Simon Mason said:
Understeer is caused by one of two things in a drivers actions. Too much speed or incorrect throttle balance timing.
To be honest I think you've *over* simplified it there. My original post was trying to describe the rather complex relationship between throttle input, and the balance of the car. In particular, gentle acceleration tends to encourage understeer, while engine breaking or hard acceleration both tend to encourage oversteer. There are other factors that determine whether a car oversteers or understeers in a given situation so when I say 'encourages oversteer' I don't mean you always get oversteer - I mean it moves the car away from understeer and towards oversteer. So you might get less understeer, or more oversteer, depending what the car was doing before. iyswim!
joospeed said:Of course it's driver induced! The car doesn't do anything on it's own does it? A car might understeer at a lower speed than another car, but it's still the driver causing the understeer. You can make any car oversteer if you try hard enough.
I don't think Simon's saying wait till the straight to apply throttle at all, but certainly there's the right moment. He was certainly encouraging me to use more throttle and earlier in my Radical, at the right point and with the right balance.
Yup i realised what was being said by Simon after i'd posted my reply. Being a typical techie with oily hands i was focussing too much on the car not the driver ..
A car with what is described as understeering bias is only understeering because the grip level has been exceeded and it's being exceed for some reason more at the front than the rear more of the time .. if you slow down you don't reach the grip level limit so it'll not understeer. On that basis what simon said makes perfect sense.
Basically if your car is sliding (or sliding more than you wish it to), you're going too fast.
A car with what is described as understeering bias is only understeering because the grip level has been exceeded and it's being exceed for some reason more at the front than the rear more of the time .. if you slow down you don't reach the grip level limit so it'll not understeer. On that basis what simon said makes perfect sense.
Basically if your car is sliding (or sliding more than you wish it to), you're going too fast.
joospeed said:
Oh my god I have to correct a few things here before some of you die
Understeer is caused by one of two things in a drivers actions. Too much speed or incorrect throttle balance timing.
Understeer on exit comes from impatient throttle input to balancing the gas too soon or too high an entry speed pushing you past the apex.
Talk of higher gears is irrelivant because once in the corner you have what you have and you deal with it relevant to the 2 above scenarios.
To counter any of the two scenarios look where your going and use logic. If you can't your cars too fast for you.
No, thats not what I've said at all. What I am saying in fact is that you have got what you've got when your in a corner, you gave it to the car based on your understanding of the circumstances your in and if you are any good as a driver you compensate for what you've given it when that circumstance has been misjudged. For sure some cars inherently understeer but if you drive them how you want rather than adapting your driving based on my earlier comment of fact then its not the car thats at fault but the driver.
We are not talking about adjusting car set up's here as I understand it we are talking about dealing with understeer a very simple and straightforward subject.
GreenV8S said:
Understeer is caused by one of two things in a drivers actions. Too much speed or incorrect throttle balance timing.
To be honest I think you've *over* simplified it there. My original post was trying to describe the rather complex relationship between throttle input, and the balance of the car. In particular, gentle acceleration tends to encourage understeer, while engine breaking or hard acceleration both tend to encourage oversteer. There are other factors that determine whether a car oversteers or understeers in a given situation so when I say 'encourages oversteer' I don't mean you always get oversteer - I mean it moves the car away from understeer and towards oversteer. So you might get less understeer, or more oversteer, depending what the car was doing before. iyswim!
The question was regarding understeer. I hate to be pedantic about this but it realy is as simple as my 2 points. If you are looking where your going and controlling then your power delivery should be such that understeer is still not an issue. If it is your once again either too fast in or you were simply on the gas too soon. How you apply gas can induce understeer but my experience on this is simple if that happens I'll bet you were on it too soon hence too gentle because you could'nt really see the end result. This brings us right back to where I started.
ok we get it now
In very slippy conditions with FWD understeer or RWD oversteer, dipping the clutch is the fastest way to regain control. Gently let the clutch in as high a gear as you can to reconnect drive/engine braking.
It's got me out of more than one spot of bother in the past. Slicks on snow at Oulton Park in particular..
It's got me out of more than one spot of bother in the past. Slicks on snow at Oulton Park in particular..
andygo said:
It's got me out of more than one spot of bother in the past. Slicks on snow at Oulton Park in particular..
Havent't got a Porsche 924 have you?? I seem to remember some lads in the snow at a snowy lincolnshire airfield having to get out & push the thing due to no traction whatsoever & they were on slicks & not a hill in sight too!!
Simon Mason said:
The question was regarding understeer. I hate to be pedantic about this but it realy is as simple as my 2 points. If you are looking where your going and controlling then your power delivery should be such that understeer is still not an issue.
I will assume we are talking rwd.
I respect your experience on this, which greatly exceeds mine, but I still think you're oversimplifying it. I agree that if you get unwanted understeer then you've failed to control the car correctly, and your suggestion that the mistake is probably carrying too much speed in or accelerating too little and too soon seems reasonable. I also agree that a suitable skilled driver will 'drive round' the understeer without any problem, and no doubt this is a skill you would teach your students. It might mean compromising the theoretically perfect line, speed and acceleration to avoid the understeer, but that's less harmfull than getting stuck in understeer.
However, assuming for a moment that drivers are not all perfect, they may still encounter understeer sometimes. My personal preference is for a setup which is mildly tail happy so understeer is not something that I normally have to worry about, but there are still one or two corners where it is a problem particularly in very tight corners in slippery conditions. I've learned to drive round/through it as necessary, but it is an acquired skill.
Having got into a situation where the car is understeering, I would say there are two ways you can respond. You can back off, avoid demanding more grip from the front wheels than they can provide, and wait for the corner to open up so you can accelerate firmly. This is the safe approach, although it is painfull to have to wait for the corner to open out before you can get on the power. The other approach is to accelerate hard enough to get through the understeer 'hump'. There is no middle ground, gentle acceleration will only make the understeer worse, you need to use enough acceleration to get out of the region of understeer and sometimes this takes a lot of torque, pottering around off cam in top gear just won't do it. But if you have enough torque available, and you have the gumption to keep piling on more and more throttle despite the understeer getting worse and worse, then you will get through the 'hump' and back into a balanced drift. This is a substantially faster way out of the corner, the car will follow a tighter line and carry more speed out, compared to nursing your understeer through the corner.
I know you know this, better than me, and I do agree that understeer is best avoided by avoiding the mistakes you pointed out. I'm just trying to point out though, that having got into understeer you don't *have* to slow down, there is an opportunity to accelerate out of it if you have enough torque compared to the available grip.
...because -
Gentle acceleration does the following:
1) unloads the front wheels, resulting in less front end grip and therefore more understeer,
2) loads the rear tyres and is only working them a little harder, therefore is unlikely to cause oversteer.
Result is a car that's understeering even more.
Lift off engine braking does the following:
1) loads the front tyres more, giving more front end grip and therefore less understeer,
2) unloads the rear tyres which, combined with the rear wheel braking force, increases tendency to oversteer
Result is a car with increasing front end grip and a tendency to snap oversteer (depending how/quickly much you lift off)
Harsh acceleration does the following:
1) unloads the front wheels a little, resulting in a little less front end grip,
2) loads the rear tyres more but breaks traction due to the significantly increases in force you're trying to put through the tyre resulting in the rears sliding as well (depending on how hard you're working them).
Result is a car with both ends sliding equal amounts (if you've got it right) and a big grin on your face
Gentle acceleration does the following:
1) unloads the front wheels, resulting in less front end grip and therefore more understeer,
2) loads the rear tyres and is only working them a little harder, therefore is unlikely to cause oversteer.
Result is a car that's understeering even more.
Lift off engine braking does the following:
1) loads the front tyres more, giving more front end grip and therefore less understeer,
2) unloads the rear tyres which, combined with the rear wheel braking force, increases tendency to oversteer
Result is a car with increasing front end grip and a tendency to snap oversteer (depending how/quickly much you lift off)
Harsh acceleration does the following:
1) unloads the front wheels a little, resulting in a little less front end grip,
2) loads the rear tyres more but breaks traction due to the significantly increases in force you're trying to put through the tyre resulting in the rears sliding as well (depending on how hard you're working them).
Result is a car with both ends sliding equal amounts (if you've got it right) and a big grin on your face
number 46 said:
'In particular, gentle acceleration tends to encourage understeer, while engine breaking or hard acceleration both tend to encourage oversteer' Interesting- How does it do that then !!!!!!
I'm afraid I don't know a short answer other than 'it just does, OK?'.
The long answer is that it's due to the rather subtle interaction between two things that happen when you accelerate or brake.
The first effect is that torque applied to the wheels uses grip in the direction of travel and leaves less grip available for lateral acceleration. Because of this effect, if you accelerate or use engine braking in a rwd car you will increase the slip angle on the rear wheels and encourage oversteer. This is a non-linear effect normally referred to as the circle of friction. What's unintuitive is that small amounts of torque have very little effect on the amount of grip left for lateral acceleration, in fact even if you use three quarters of the available grip for acceleration/braking you still have roughly three quarters left for lateral acceleration. This can seem quite strange unless you're use to dealing with vectors.
The second effect is caused by weight transfer between the front and rear axles. Acceleration transfers weight off the front wheels onto the rear. For a given lateral acceleration this increases the slip angle at the front and reduces it at the rear - it encourages understeer. This is a linear effect - twice the acceleration causes twice the weight transfer. Notice that this tends to counteract the first effect. As you accelerate there is one effect causing understeer and one causing oversteer. So what happens? The answer is quite interesting (well I think so anyway). Under gentle acceleration the second effect dominates and you get understeer. Under hard acceleration the first effect dominates and you get oversteer. Of course the terms 'gentle' and 'hard' are relative to the amount of grip and the center of gravity height and wheel base of the car.
Finally think what happens when you apply engine braking. In this case both effects increase slip angle at the rear wheels and encourage oversteer. Lifting off mid-bend is a good way to end up in the scenery if you are in a powerful rwd car.
Hope this makes sense, it's rather hard to explain it without pictures!
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