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Astraist
Master Driver



Joined: Mar 27, 2010
Posts: 209

PostPosted: Tue Nov 30, 2010 6:20 pm Reply with quote Back to top

I post this to bring into awarness certain cases of lack in accuracy in the site's encyclopedia. However strict it might seem, these comments have a profound effect on the understanding of the subject and on practical aspects of such important subjects. Road-Handling is the attitude of the car. Remember, cars never skid, their tires do. So, not all "skids" are alike. It's all a question of which wheel or axle slides first. If the front wheels of a certain car be more prone to slide, that would be considered a handling characteristic of that car.

When the front wheels start to slide first, the result is UNDERSTEER. Simple, the front wheels have the task of turning the car into the corner: You turn the wheel which tilts the front wheels into the corner. Get them to slide, and you get in their way of doing their job as required, so they won't turn you as tightly as you wished. Seemingly, the car would run at a wider arc, and sometimes plough almost straight ahead with lack of obedience to the steering. I guess no further explaination is needed as to why it's called UNDER-steer...How to recover? Tires can only do so much for you. Therefore, if you get them over their maximal turning capablities (=understeer), turning them more is not going to make matters better -- it's actually going to make them worst. Now, this is somewhat theoretical, because sliding wheels are slowing down and slowing down helps get over understeer, so yes, turning the wheel more CAN/MIGHT work.

The point is, for something to might work or to work in a limited range of effectiveness, is not what we are striving for. Just becuase it WORKS, does not make it proper. You can spend a lifetime of driving without a seatbelt and nothing bad would happen, but is it the right way to drive? No! The same applies here. Why? Because you turn the wheel, front wheels slide. As they slide, you turn the wheel more, the front wheels slide more and slow down more. Now what? You just turn more and more steering and than you run out of steering, but the car is yet to loose enough speed, so you just wait for it. But, meanwhile, the car is sliding towards the edge of the road. What do you think is more likely to run out first: The road or the speed?

Furthermore, not only will the response be delayed, but also -- it would appear more suddenly. Recap: You turn the wheel, but the front keeps on sliding forward. You turn more, which seems to carry no immediate effect. You turn more and more as much as possible and wait. Now, let's say you somehow got it to turn again, the car will now "find out" you have turned the wheel all the way into the corner and it will sharply tighten the line, which mike rock it into a spin. Okay, so that's UNDERSTEER. You turn into a corner, you make a mistake (too much speed/gas or even too much braking) and the front wheels slide and refuse to turn as tightly. You run too wide towards the armco. What to do? REMOVE THE CAUSE. In understeer, this is simple: Whether it's too much speed or too much acceleration, the solution is to reduce the throttle input, maybe go off throttle and maybe even brake a bit with ease. This gets you to slow down faster, and without making it harder for the front wheels by turning them more. Here's an example.

That's also why understeer is the natural tendency of all cars. ALL road cars and race cars, with the exception of a few rally cars and some drifting-cars, are all tuned to understeer. You get into a slide, you brake, and you get things sorted. Natural. In light of this, the claim of the "Encyclopedia" that front-wheel drive cars naturally tend to understeer while rear-wheel drive tends to oversteer -- is spectacularly not true!

Now. Oversteer. If understeer is the sliding of the front wheels, oversteer is the sliding of the rear wheels. Why the name of OVERSTEER? Because the front wheels have the job of turning the car into the corner, but what does the rear do? It has the job of keeping the tail of the car to follow the trail of the front wheels through the corner. If they slide, the tail "Swings" aside.

When the tail swings aside, it rotates the front too much into the corner, and the car momentarily over-steers, and than spins all the way around. This is a result of one of two things:
1. A forward weight transfer: You brake sharply in a corner and the car nosedives over the front-wheels, and the rear wheels might actually become airborne and swing aside.
2. In a powerfull rear-wheel drive, TOO MUCH throttle can get you the same result.

The encyclopedia claims two false claims regarding oversteer, both related to the corrective input. Here the mistakes are more crucial and I will quote them directly:

Quote:
"With oversteer rear wheels will lose traction, sending the car into spin. The same instinctive driver [braking] behavior will amplify the problem and guarantee complete loss of control over the car, when front wheels are forced by spinning car to lose their traction, too. There is a technique called opposite lock, however, that allows driver to keep the control and even use slight spinning to complete the turn on higher speed. I consider this technique to be a survival skill and absolute necessity to anyone driving RWD car. When mastered, it allows the driver to get much more fun out of driving, by the way.
"


In order to make it more clear, I will refer to them according to the context and not the order in the quoted text. First, of correcting oversteer by applying what is called "Opposite Lock". That is not the appropriate correction! Like with understeer, trying to fight with the car by forcing it to turn to where the wheels are pointing, is not very effective in serious situations. If the case I presented above, when a driver brakes ubruptly mid-corner, causing the rear to kick around, what should the driver do? Turn the wheel against the slide helps by what exactly? The only thing that will really help is to get off of the brakes and ON THE GAS. This will get the car to squat over it's rear wheels and pull it forward and straight ahead. Trying to correct by steering alone would result in one of the following:

1. Either the car would spin even though you applied opposite lock.
2. The car will spin HARDER
3. The car will be sent off in the other way (again harder)
4. The car will not spin, but will also not stop sliding. You will again find yourself turning more and more steering, untill you run out of the steering, than either run out of momentum and straighten-up, or run out of road and hit the armco sideways.
5. The car might pull back straight.

It's not that you do not need to apply opposite lock, it's just that it's not the most important step nessecary to recover. Furthermore, most of our roadcar are Front-wheel driven. In front-wheel drive car, throttle takes extreme importance relative to the steering correction. It is in fact so much more important, that you SHOULDN'T apply opposite lock in a front-wheel drive car! You just straight the steering and accelerate forward, and maybe steer very slightly and briefly to the other way at most. Furthermore, in any case, the attempt to recover from oversteer in any of these methods is very complex and unless the driver has had a great deal of experience with oversteer recovery (and one skidpad tuition is not a "great deal of experience"), the driver should do something else and that is...
STEP ON THE BRAKES, and HARD! Yes, that would increase the weight transfer that creates the spin, BUT! It also reduces speed very quickely, which reduces the forces which are sliding the car exponentially from second to second. Furthermore, it either locks-up the wheels or activates ABS, which further helps in stopping the spin and maybe straighten the car! Here's an example.

Hope my input is welcome...

Summary
Understeer: When the front wheels slide and the car runs wide and out of the corner. The natural tendency of all cars. It's identification is through a sense of "light" steering. It's correction: By slowing down GENTLY by reducing the throttle input or gently applying the brakes. NOT by steering more tightly. The AVOIDANCE: Entering bends slowely, keeping constant throttle in the corner, accelerating out of it gently.

Oversteer: When the rear wheels slide and seek to spin the car around. Identification: Sensation of very heavy steering and feeling of the car's rotation through the back of the seat. Correction: In theory, by a carefull application of throttle while making the nessecary steering correction. In a FWD, you straighten the wheel and accelerate forward. In a rear-wheel-drive (or all-wheel-drive) you maintain constant throttle while applying opposite lock. For the unskilled, just brake HARD.

AVOIDANCE -- avoid hard braking mid-corner. Be gentle. Slow down befre the corner and keep constant throttle in the bend.

Problems with the "Encyclopedia":
1. UNDERSTEER is the natural tendency of ALL cars.
2. OPPOSITE LOCK is not the main step for recovering from oversteer.
3. OVERSTEER in a Front-wheel drive should not be corrected by opposite lock at all.
4. OPPOSITE LOCK and OVERSTEER recovery in general are difficult and without the right training in an advanced driving school -- the driver's best choice is to brake very hard.
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Misha
Site Owner



Joined: Aug 02, 2006
Posts: 704
Location: McLean, VA, USA

PostPosted: Tue Nov 30, 2010 10:22 pm Reply with quote Back to top

Braking very hard is rarely a best choice - as my experience shows. YMMV of course Smile

I think your passion is not quite justified here, the most part of the oversteer article and the entire opposite lock article deals with the RWD cars classically tuned in terms of steering response, and most of your critique deals with modern FWD cars. No question about it, with FWD or rather understeer the answer to losing control in the turn is moderate breaking. Moderate, I am quite sure in it, cause with hard breaking under the circumstances when you already lost some traction you are likely to lose all the traction or at least rear traction and come to unfamiliar territory of oversteer. Yes, understeer pushed beyond its limits this way becomes oversteer, and this transition is quite nasty and almost guarantees some kind of accident.

And looks like you never tried the opposite lock. Try it, it's fun Smile
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Astraist
Master Driver



Joined: Mar 27, 2010
Posts: 209

PostPosted: Wed Dec 01, 2010 5:58 am Reply with quote Back to top

I'm sorry if this brings up hard feelings. I don't want to stat an arguement.

Misha wrote:
Braking very hard is rarely a best choice - as my experience shows. YMMV of course Smile


Didn't say it was. It's the choice for the unskilled. In order to acquire good skid recovery capabilities, it takes much longer than the one-day advanced/defensive driving courses that are held in some institutions. Anything we do in driving -- especially skid recovery -- depends on many factors that relate to the given the situation, the car and the road. Another aspect often overlooked in the driver himself and his level of skill. There is a different solution for situations for the skilled and unskilled.

The same advice I give here is the advice given in various presitigious institutions and race tracks like PalmerSports in Bedford, GET in Cergy, Ecole de pilotage en Loheac, Circuit de Laquais and others...

Misha wrote:
I think your passion is not quite justified here, the most part of the oversteer article and the entire opposite lock article deals with the RWD cars classically tuned in terms of steering response, and most of your critique deals with modern FWD cars.


Well, if it does refer to rear-wheel drive than it's not that bad. Most of my critique relates to front-wheel drive because that's what most people are driving/will drive on. Besides, I have made strong points regarding rear-wheel drive cars too: First, that they are also tuned for understeer. Second, that the corrective input is not made strickly out of applying opposite lock, but rather:
1. Constant throttle: Applying just enough gas to keep the car at the same speed all the way. This step is more important than the mere application of opposite lock!
2. Opposite lock: Steering the other way and than back straight.


Misha wrote:
No question about it, with FWD or rather understeer the answer to losing control in the turn is moderate breaking. Moderate, I am quite sure in it, cause with hard breaking under the circumstances when you already lost some traction you are likely to lose all the traction or at least rear traction and come to unfamiliar territory of oversteer. Yes, understeer pushed beyond its limits this way becomes oversteer, and this transition is quite nasty and almost guarantees some kind of accident.


On that we agree. The solution for understeer: Is to gently roll onto the brakes, as stated in the video I supplied. But, what if the understeer got totally out of the driver's hands ("Terminal understeer") or what if the driver got into the far more complex situation of oversteer? The solution is to brake very hard. Braking only turns understeer to oversteer (or aggrevates an existent oversteer) if the driver does not brake hard enough. If he does brake hard enough, he is likely to wipe off a lot of speed, probably stop before the obstacle (or hit it very very slowely) and in the event of oversteer, it can pull you back straight.

Misha wrote:
And looks like you never tried the opposite lock. Try it, it's fun Smile


Oh, I have tried it. I deal with oversteer/understeer in every time a rent a SkidCar for practice or when I go lapping around a track, on rally stages and in empty spaces of wet tarmac, gravel or mud, especially when instructing students. I have experienced these situations in various places, speeds and on various surfaces. I tell you what is more fun than applying opposite lock -- pulling back a FWD from oversteer by the mere spinning of the front wheels and likewise, keeping a rear-wheel drive sideways by keeping the rear spinning during opposite lock. Now that's good fun!
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Misha
Site Owner



Joined: Aug 02, 2006
Posts: 704
Location: McLean, VA, USA

PostPosted: Wed Dec 01, 2010 7:01 pm Reply with quote Back to top

We seem to be not far away on most of the things you mention. And it certainly does not cause any hard feelings. In fact I promoted your original post to the homepage cause I think it is quite useful for younger drivers and will kick start them thinking Smile
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kooper
New member



Joined: Feb 24, 2012
Posts: 3

PostPosted: Fri Feb 24, 2012 1:05 am Reply with quote Back to top

What you track a cell phone present here is rather exhaustive. In other words, oversteer is when the rear tyres run the larger slip angle or reaches their limit first? I think, good balance is therefore essential for maximum cornering capability and has been the aim of most of the previous drivel


Last edited by kooper on Thu Apr 12, 2012 2:20 am; edited 1 time in total
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Anturako
New member



Joined: Mar 01, 2012
Posts: 3

PostPosted: Thu Mar 01, 2012 7:11 am Reply with quote Back to top

I have the 17in rims on the limited model and I've noticed this as well. I mean its not the best handling car especially coming from a G35 sedan.. Handling is night and day... imo to correct your problem honestly is to get either coilover suspension or some performance springs that will lower the car about an in or so.. nothing too aggressive with the front tower strut bar. That will surely solve the handling issue.
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sgtrock21
Seasoned Driver



Joined: Jul 15, 2012
Posts: 120

PostPosted: Sun Jul 15, 2012 6:35 pm Reply with quote Back to top

I started driving at the age of 13 with rear wheel drive cars. When I transfered to front wheel drive I experienced a few near and actual accidents. This was do to the ingrained tendency to reverse lock in a skid. I like how understeer vs oversteer is explained in NASCAR (lot's of power, on the edge traction, and rear wheel drive). "If you are experiencing severe understeer. You will see the wreck"!
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