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Old 06-01-2003, 06:36 PM   #1
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Overstear/Understear: What does it mean???

Anyone who can help, I would greatly appreciate the automotive lesson.

I always read about this, but I never know what it means.

What is it??

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Old 06-01-2003, 06:54 PM   #2
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You can think of oversteer as in the car turning more than you want. Personally, I call it 'kicking the tail out'. You oversteer when you slide or drift around a corner. Very fun.

Understeer is when the car doesn't turn as much as you want it to turn. This is also called pushing. Like if you're ignorant and brake hard and turn at the same time, you're just going to lock the front wheels and go straight instead of turning.
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Old 06-01-2003, 07:23 PM   #3
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Quote:
Originally posted by Ahura
You can think of oversteer as in the car turning more than you want. Personally, I call it 'kicking the tail out'. You oversteer when you slide or drift around a corner. Very fun.

Understeer is when the car doesn't turn as much as you want it to turn. This is also called pushing. Like if you're ignorant and brake hard and turn at the same time, you're just going to lock the front wheels and go straight instead of turning.
Sound Ahura is glorifying the oversteer and understeer. It is something that slow you down and should try to avoid. Too much oversteer will make you spin too. To correct under and oversteer there are two ways - depends on the situation. Either lift off your gas or slam on the brake - this what you are doing when you are understeering anyway.
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Old 06-01-2003, 08:20 PM   #4
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When you are talking about performance driving, oversteer and understeer can be very slight. But to explain it easier, one would use extreme examples, like Ahura did.

An extreme example of understeer (or "push", or in Nascar, "tight") that most drivers can relate to is when you are driving on a rainy, snowy, or icy road. Understeer is when you turn the wheel, but the road is so slippery that the car doesn't turn, or at least only turns half as much as it normally would. In other words, it doesn't steer as much, or "understeers" (like "underachieves"). Or, it "pushes" forward instead of turning. Basically, the front does not have as much grip as the rear at that point. It's normally not as extreme as driving too fast on a slippery road (unless something is really bad). It's normally something that's more subtle, and only shows up when you drive the car at or near the limits. It will not show up just driving around town or down the freeway (again, unless something is not right), which is why the general public doesn't notice or care that most cars have a tendency to understeer.

An extreme example of oversteer (or "loose") that most drivers can relate to is when you are driving on a rainy, snowy, or icy road. Oversteer is when you are going around a curve, and the tail of the car looses grip, and the car goes into a slide (the type where your driving instructor always tells you to "turn into the slide, turn into the direction that you are sliding"). In other words, the car steered too much, or "oversteered". Or, the back-end of the car came "loose", and swung out. In this case, the rear does not have as much grip as the front.

A car will either be "balanced" or "neutral", or have a tendency for oversteer or understeer. In most cases, regular drivers can handle an understeer or "push" situation alot better than an oversteer, or "loose" situation. So, most street driven vehicles, especially ones that aren't meant for performance, normally have a tendency for understeer.

Regardless of whether a car is balanced, or has a tendency for oversteer or understeer, what occurs in a corner depends on how you drive it. Bad driving can make a balanced car oversteer or understeer, or turn a slight understeer into a big one. While a good driver can drive the car in a certain way that minimizes the effects of an understeer or oversteer.

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Old 06-01-2003, 08:52 PM   #5
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My favorite 3 books on high performance driving all explain oversteer/neutral/understeer (and tons more about high performance driving) in more detail than anyone could here. I don't think anything said so far is wrong (although Sputnik had an excellent point that "oversteer" can and should be much, much more slight than "kicking the tail out"), but there's so much more to those terms. Oversteer can be used to denote a tendency a car has, while "kicking the tail out" is a flashy but extremely slow way to drive any car - even one that "understeers". Fun, yes, but not fast.

The first 2 books are cheap, so I would highly recommend picking them up. I think "Going Faster" is close to $30, so depending on your budget it might be too expensive. I've heard that it's worth it to read before any racing school. Much of what they discuss is more track oriented than autocross oriented, although the fundamentals are the same. Since I autocross and don't race on a track, it's a bit less useful to me.

Paul Frere's "Sports Car and Competition Driving" - A classic, and a must read for driving enthusiasts. Some parts (like slip angle) get a bit technical, but I found that re-reading it after a few months of racing really helped.
Henry A. Watts' "Secrets of Solo Racing" - Wonderful introduction to autocrossing. I think it's like $11 on amazon. That's a steal if you're going to ever do any autocrossing. It's so cheap that it's almost stupid to go to your first autocross without having read it. Of course, you probably won't know about it until after you've been at a bunch of autocrosses.
Carl Lopez's "Going Faster! - Mastering the Art of Race Driving" - The Skip Barber Racing School - More technical than the others, and far more detailed. Loaded with pictures and graphics that really drive home what they're discussing. If you're a visual learner, this might be the best one.

Last edited by Rich; 06-01-2003 at 08:57 PM.
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Old 06-02-2003, 02:30 PM   #6
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as you guys note the ideal situation is a neutral car,

but of course that's an ideal that's ultimately impossible (at the limit)

the trick is getting a car that progressively moves into over or under steer, personally I prefer a car that oversteers at the limit as a quick steering switch will normally save you, on narrow uk roads you don't want to understeer on a left hander.

it's when a car behave's in a non progressive fashion you really have to worry, ever seen an old MR 911 doing a pirouette on a country road, usually goes something along the line of :
kerb, hedge, sky, ground, sky ground, sky, ground etc.
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Old 06-02-2003, 03:26 PM   #7
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Quote:
Originally posted by KEF
as you guys note the ideal situation is a neutral car, but of course that's an ideal that's ultimately impossible (at the limit)

the trick is getting a car that progressively moves into over or under steer, personally I prefer a car that oversteers at the limit as a quick steering switch will normally save you, on narrow uk roads you don't want to understeer on a left hander.
it is difficult to have a neutral car at the limit, but depending upon the mechanical (static) characteristics of the car, and the (dynamic) conditions at said "limit" are, you could have a car which is very close to neutral until grip fails you( a nice, even, four wheel slide), but then with a very quirky attitude (under or over steering) when well under the limit... anyways, it's an extremely case-based situation... the tiniest of discrepencies in design or even mass (ie fuel load) can have a large difference, so it's hard to talk about in very general terms.

anyways, as to which is better to set the car up for, constructors dial-in understeer from the factory because most drivers suck, and instinctively hit the brakes when heading for something which isn't open road (ie, a wall, people, oncoming traffic) rather than steering out of a slide, which in a situation dealing with understeer and a softly sprung car (which in such a dynamic situation would have most of the weight transferred to the front wheels) is certainly the safer setup... it's just a comprimise, another one of those conditional, subjective things which is difficult to apply in general terms.
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Old 06-03-2003, 12:04 AM   #8
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http://www.johnnyoconnell.com/tips3.html

In racing, the ideal set-up is slight oversteer in slow corners (eg hairpin turns) and slight understeer in fast corners.

Good book on driving: "Drive to Win"
http://www.carrollsmith.com/books/index.html

Last edited by Supercharger; 06-03-2003 at 12:14 AM.
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Old 06-03-2003, 12:04 AM
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