If the rear tires are at an excessive slip angle, then turning the fronts inwards means that they have even more excessive slip angle.
With LFS S2, at least in the case of the LX6, if the rears aren't sliding, then inducing understeer is extremely easy, but once the rears start to go, it's seems to be very difficult. This is what I don't understand. With LFS S1's all or nothing grip, inducing understeer was very easy, even more so than GPL, as shown in this video:
I've tried messing with setups in attempt to be able to get the front end to wash out after losing the rear end (if I center the steering or steer inwards), and I find I have to max out front sway bar, zero out rear sway bar, and mess with camber settings to just get the car to slide sideways evenly. I'm running minimum pressures in the tires of the LX6 and yet the middles are still the hottest points. I could try increasing front tire pressure while leaving the rears at 11 psi.
Induced understeer to recover from oversteer works in real life for most cars. If you have access to a large empty parking lot, you can try this for yourself.
OK, got the induced understeer to work, but it took increasing the steering lock to 30+ degrees (I maxed it out to 36 degrees), I can transition from oversteer to understeer with a lot of inwards steering input. However, I don't need anywhere near this much steering lock to induce understeer if the rears aren't sliding. Still puzzling me why the rears sliding affects what happens at the front end so much, especially when the car is oversteering, the front tires slip angle is already increased.
How can this be? Front slip angle is greater than rear slip angle unless you counter steer. The assumption in this case is the fronts are still turned inwards. If the rear tires are spinning because of excessive throttle, there's a small window of time before the slip angle at the rear goes beyond optimal, and you can just lift a bit and/or counter steer.
Generally induced understeer is used in two cases. When a car is slowing, normally you don't get understeer unless the driver downshifts too soon and breaks the rears loose, or the car setup is just too oversteery under lift thottle. In this case induced understeer works well because you can use it while braking. The other case for using induced understeer is in a very high speed turn, where the throttle is floored just to keep the car going against the aerodynamic drag from the high speed. Under this circumstance, the rear tires are driving the car forwards as well as trying to turn the car. Keeping the fronts turned inwards just a bit past optimum can stabilize a car, if the rear end steps out, the increase in slip angle at the front results in the car just drifting instead of oversteering. It's just a bit past optimum, because any more than that and you create too much drag and heat on the tires. It's more of a preventitive method than a recovery method. Again, it's not going to help if the car isn't properly setup for high speed turns.
Countersteering is normally used during acceleration, similar to drifting, or rally style driving, or dirt tracks. You modulate the throttle and steering inputs to control the car. Countersteering and braking don't mix, the reduced slip angle at the fronts allows them to have more available braking grip than the already sliding rear tires and just makes the spin worse.
I agree that induced understeer can be used as a preventative measure to stop the rear from stepping out. I saw F1 drivers doing this at Suzuka in the wet two weeks ago. I haven't got any footage though, as it was in FP.
What's that got to do with it? Understeer is how you correct slides. That's why if you drift slightly around a corner at the same speed you will have run wide from your usual line.
And if you're sliding around a lot then it tends to be the middle of the tyre that heats up, I've found (with smooth driving) the LX4/6 to be the easiest car in which to get pretty even temperatures across the tyre.
J.B. is right. If the front SA > rear SA then you have understeer by definition. If you're in a spin, the rear SA > front and you're in an oversteer situation. The full SAE definitions are a bit more involved than that, but that's pretty much how it's defined.
An alternate definition of understeer versus oversteer, at least in terms of defining a car's setup.
You drive a car around in a circle, well below the limits. It takes a certain amount of inwards steering input to maintain the circle. Then, while holding this radius, you speed up the car until it is near the limits. The steering inputs required to maintain the raidus determine if the setup has understeer or oversteer.
Understeer - it takes more inwards steering to maintain the radius.
Neutral - it takes the same amount of inwards steering to maintian the radius.
Oversteer - it takes less inwards steering to maintain the radius.
Critical Oversteer - The steering is centered while maintaining the radius.
Critical oversteer isn't a limit, because rally cars and dirt track racing go beyond this.
That's close enough for government work and probably good enough for general discussion
If we want to be picky though this isn't really right. All that matters is what the slip angles are at the end of the day. Basically, if you're running around the circle and you're not needing to countersteer to keep the car from spinning, then the car is either in an understeer or neutral state. Whether or not you had to increase steering lock into the turn to maintain the circle doesn't really matter. You could have been running 5 degrees front slip angle and 3 rear at low speed, then kept the steering right where it was while speeding up. If you wind up at 10 front and 8 rear slip angles, the car is still understeering even though you haven't steered into the turn at all to maintain the circle. In fact, if you countersteered 1 degree to get 9 front and 8 rear, you're still in an understeer condition.
Neutral technically means the front/rear slip angles are the same.
For all practical purposes, if the car doesn't spin out it's understeering or neutral, so your description is probably close enough
As for the LX6 stuff, I'll need to reread some of the later posts to comment.
Regarding the slip angle versus lateral force (grip), here's a link that describes the differences between radials and bias ply racing tires, along with a graph. I think the radial curve dropts off steeper than it does in real life for racinc radials.
If LFS doesn't allow slicks for all cars, then it should at least allow DOT racing tires, which are typically bias ply, and provide grip aroung 1.2 to 1.3g's, right between the road supers and slicks of LFS, but with the stability of the slicks, because they are usually bias bly. In real life, most racing classes permit the use of the equivalent of a DOT racing tire. (In the USA, DOT just means that the tire is street legal).
Another link including a graph comparing slip angle versus lateral force versus normal force. Note that at low normal force, the curves lost almost no grip when beyond optimal slip angle. These curves are for racing radials. Bias ply slicks have much less or no loss in grip at fairly high slip angles.
If the car begins to oversteer, slip angles must be larger at the rear. Just because you can control the slide with the wheel centered makes no difference. It is still oversteer because the radius of turn of the front wheel (infinite) is larger than the rear wheels (something less than infinite). So by definition it's oversteer. It's in the name!
And what do you think the slip angles are when you're driving in a straight line? I'd say they are equal.
I'm talking about what happens after a car stabilizes into a fixed yaw angle while turning. Think of this as the slip angle for the entire car. The car is pointed inwards relative to the direction it's actually traveling while turning.
My impression was that the only way for all 4 tires to have the same slip angle while turning is for the steering wheel to be centered when turning (and no ackerman effects at the front). In LFS, this can be setup with the LX6 with slicks, via the slick mod, with near equal front and rear sway bar settings (I couldn't get this to work with the road supers as they are too unstable).
However what I left out is the rate or rotation of the car as it turns. The car is yawing in the direction of the turn while it is turning. This means the front end is moving inwards, and the rear end is moving outwards relative to the center of rotation of a car in a turn. However, relative to the path of the car, both the front and rear end of a car are moving inwards.
I've found some web sites with questionable diagrams of slip angles when explaining understeer / oversteer, such at this one:
The issue is that the diagram shows the front slip angle as inwards versus straight ahead, and rear slip angle as straight ahead versus outwards, for the neutral and oversteer cases. Based on these diagrams, the implied path of the front end of the car is the same as the direction that the car is pointed in, for both the neutral and the oversteer case, while at the same time, the implied path at the rear end of the car is outwards.
Obviously, there is no slip angle at the rear end of a car unless the rear end of a car is yawed inwards relative to it's path. Assuming the car isn't hinged in the middle the entire car is yawed inwards at the same angle. This is pretty obvious in the case of tires with large slip angles, similated in games like GPL or GTL.
I thought of a good example regarding slip angles.
Take the case of a car moving forwards on a steeply banked straight. The actual path direction vectors for both the front and rear of a car are parallel: their directions are identical front and rear. Yet the car will have an overall yaw angle, pointed slightly up slope on the banked section of track.
In order for slip angles to be the same front and rear, the steering has to be centered.
I prefer a steering input based definition for understeer versus oversteer. Maybe new terms are needed.
Steering understeer - as the amount of bank of the straight is increased, it takes more steering input to keep the car going straight.
Neutral steering - as the amount of bank of the straight is increased, it takes the same steering input to keep the car going straight.
Steering oversteer - as the amount of bank of the straight is increased, it takes less steering input to keep the car going straight.
Steering critical oversteer - as the amount of bank of the straight is increased, the steering wheel approaches being centered.
OK, so take this example:
Your rear brakes loose in the GTT for example, and you have to pile on loads of opposite lock to stop the car from spinning. You put on just enough luck to stop the car from spinning, but not enough to reel the rear back in. So you're now pulling a huge powerslide (some call it drifting, I'm sure there's some subtle difference in definition, but anyway). But you're not going to spin. And the rear isn't coming back into line. So slip angles must be equal and you've still got lots of lock on.
In this case, the rear slip angles are much higher than front slip angles. You see this all the time at drift events, rally events, and dirt track events. There's no rule that states slip angles have to be the same to prevent a car from rotating (yaw rate) faster or slower than it needs to in order to take a turn.
In the case of donuts, you can have the inside front barely moving at all, virtually no slip angle, while the rear tires have a huge slip angle, as in the second half of this video:
Anyway, all of this is getting a bit off topic. I'm trying to understand why some LFS cars like the LX6 reacts so severely when the rear end gets a bit loose. I tried using the setup parameters so if the LX6 is sliding sideways, the front end has less grip than the rear. In addition to sway bars maxed at front and zero at rear, I had to also mess with the camber settings to get the result I wanted. The net result is a LX6 that is a lot easier to drive, but I don't understand why it takes such an extreme setup to get it to behave itself.
If you want to try it out, here's the test setup I created for Blackwood:
Well, I tried your set, and I wouldn't really call it easy to drive, it's just pig understeer at every corner. OK so it doesn't spin so easily, but you couldn't actually use a set like that for anything other than "this set doesn't spin much".
I fiddled with it a bit to try and make it somewhat sweeter to drive, ended up having to change a lot. I could keep it on the track even with my demented pedals. See what you think - it's not that bad a handler surely?
Wow! Your (and Milliken's) contributions to this thread are making my head spin. Great stuff. So... I've always felt that the car or kart or bike or skateboard is really at it's peak when it starts to get "squirmy". That's been my interpretation. My buddies and I used to trade cars in highschool and we'd talk about where the car "floats". I'd say, "In my car you want it to float around the shifter." Dave would say, "To drive my car right it needs to float around where the backs of the front seats meet the frame." We we're talking about where you put the sense of rotation in a particular chassis to drive it neutral. But to get to float, we were always refering to the tires. Float only happened once the tires were at the limit. If that's making any sense.
So, LX6. LFS. I have no idea where I'm going with this. I've always felt that the fronts over commit, perceptually or actually, in certain cars more than others, in LFS. Like, they get more grip, more quickly, and with less feedback than the rears. I have been lowering and lowering cambers to make the cars "float" more. I find that if the cambers are too high, the car (or end of car) commits at a level that I can't percieve. The imbalance in handling then becomes a result of me providing steering or throttle input that I am not aware of until it's far too late. (Commited.) I was just driving a FOX around that I think is quite nuetral, front cambers are at 1.40, rears at 1.90. I wanted it to oversteer a little more, changed rear camber to 1.83, and got the desired result. I am more and more, tuning the "feel" of the tires with camber.
In the LX6 front camber is key to the radical mid and late corner oversteer for me. I have noticed that a lot of people set up the LX6 to understeer like cazy with very stiff front ends. All fine and dandy under the limit, making the car not spin crazy, but also making a car that doesn't turn in well and becomes a bear by the time it does get pitched. In the LX6 my cambers are well below 1 degree in front. Bars are at a minimum, and spings medium with less sping in front. The car seems to rotate well, and is easy to read front and rear without that over commitment in the front end that I think I'm not feeling.
So what does any of this have to do with any of that? Heck if I know. I don't understand most of this thread. Some of the steering angle setup stuff seems really important, especially in the LX6. I understand what caster is geometrically at the front axle, but am having a hard time picturing how it affects the rest of the car through cornering phases. Add to that, suspension geometry, rates, and slip angle correlations and I'm completely lost.
In the end, I think that a lot of the problem is perceptual. You can set the car up to act properly, with acceptable grip and balance through the cornering phases. Reading what it is doing is entirely another task.
As someone else posted, reducing front camber (which I did) seems to help. Regarding my understeery setup, on the skid pad the sustained g-forces while cornering remain about the same.
Did you see more than a 1 second per lap difference between the two setups? My issue is I'm just not that fast with LFS, my Blackwood times are barely under 1:25. You're probably a lot faster.
Perception has a massive impact on the LX cars. Cars like the LX series are strange as you have a light car with a massive power to weight ratio. You also sit right over the rear wheels so you feel everything that is going on the instant that it does happen. Everyone I know that owns a real car like this say it tells you exactly what is going on so its very hard to spin out, or to be more exact you correct it as soon as you detect the problem. (the fear of death/injury normally makes you do this )
All this means that IRL you become far more subtle with your inputs than you would in LFS. That is not to say there are issue with the tire model but the LX really suffer from over driving more than other cars in LFS.
I understand exactly what you mean by the squirmy/float feel cars get on the edge. All of a sudden you get "that" feeling start to build and you know if you push much harder you are in the problem zone. But due to the feedback of what is going on IRL it becomes easy to hold it on that edge in a well setup car. My BWM Mini Cooper was classic in this as it was stiff enough to left you power through roundabouts well into slip angle and move between power understeer and liftoff oversteer to get you round the corner with the most power it was possible to put through the front wheels at any given instant. Trouble is that this feeling and level of feedback is not possible to give through a FF wheel as most of the feeling comes through your body and ears (ears being the key to your feeling of G and balance)
Is there a solution to this? probably not without getting a motion platform. It might be possible to give some clues with fake FF effects but personally I am against this route as it would cloud the great feel the FF currently has.
I own a Caterham SV with a 2.3 liter Ford Duratech with about 250hp. This is the first car I've ever experienced lift throttle oversteer with (however the car recovered very quickly, much quicker than my heartrate did). Recovery seems much easier than it does in LFS, but as posted, it's because you can feel the rear end getting loose much sooner than you can with LFS. One thing that would help would be for tire scrub sounds to occur further below the limits than they do now with LFS. In a real car, you can hear scrub sounds well below the limits of traction (at slower speeds where wind noise doesn't block out the sounds).
