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Old 4th June 2004, 18:05   #1
Tom
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Guys,

Can u pls explain in simple words what causes a car to overteer and understeer?

thanks,
Tom
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Old 4th June 2004, 18:16   #2
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Well ummm.... Generally..
Rear Wheel Drive Cars OverSteer
Front Wheel Drive Cars UnderSteer
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Old 4th June 2004, 20:22   #3
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When you are turning into a corner, and the car just goes on straight and refuses to turn in as you would expect, thats understeer. Understeer is more common in front wheel drive cars.
Oversteer happens when the car refuses to get back into a straight line after turning in. Thats when the you feel the back end of the car has a mind of its own. If you have need for speed porsche unlimited, try playing the game with the older porsches with only rear wheel drive. You will get a feel of oversteer there itself. The older porsches were notorious for their tail happy behaviour.
Best is to have a car with neutral handling, niether under or oversteer. 4 wheel drive eliminates this problem to a large extent. But then u cant have tire smoking exits.
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Old 4th June 2004, 22:34   #4
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Quote:
Originally Posted by [b
Quote[/b] ] 4 wheel drive eliminates this problem to a large extent.
Not always pal. It does to some extent, but its no guarantee. Older gen A6 and A4 quattros did show signs of understeer, and not in small but substantial amounts. Why, you can even provoke the newer Gallardo into Oversteer moments.

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Old 5th June 2004, 00:51   #5
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In a 4wd system, it also depends on how much power is transmitted to the front and back wheels, doesnt it? Hope this problem has been sorted out in the new cars. Otherwise there are always electronic gizmos to take care of this now. So if you want to have a little fun, all u have to do is switch off the electronics, if they allow u to do so that is.

The oversteer understeer also has to do with the chassis dynamics, suspension setup, weight distribution.
I tried all this things while playing indycar racing and nascar racing. You can tweak a little bit here and there and feel the results immediately on the track. Its all black magic for me though. lol.

Speaking of the Gallardo. You have 500 horses willing to do what you want them to do, isnt it? *

rtech should be the best to answer this post with his track experience. Over to you rtech.

If anyone of you guys have indycar racing 2 by papyrus and are willing to part with it, i would be extremely glad to have it.



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Old 5th June 2004, 01:53   #6
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Hehe, n4s, play Colin McRae, harden the suspensions a wee bit and watch how the car oversteers.

Yes, modern day 4wd systems have improved. Look at R34 and 911 turbo. They both have variable power being sent to the front and back, with more at the rear than the front. It helps more so if you can't get the ideal 50-50 weight distribution setup, a problem in cars like the Porsche where the engine sits at the rear.

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Old 5th June 2004, 02:16   #7
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well when it comes to breaking the understeer=FWD connection nobody does it better than the new MINI.
i have seen that car oversteer out of a corner just like any RWD. it all about your suspension setup. besides hatchbacks are very tail-happy.
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Old 5th June 2004, 04:29   #8
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pal i'll tell you, even tyre pressures can affect steer. Even my wagon r someimes has oversteer when there's more traction on the front wheels.

keep the rear tyre pressure 3-4 psi more than the front wheels, take the car to it's limits and then see what happens.

your toe angles on the front wheels also affect steer. "Toe out" will help get the car into corners much faster and "Toe in" will provide stability at high speeds.

there is no end to what you can do to your cars handling.

"the smallest things, sometimes can make the biggest difference".

Regards...
Shan2nu
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Old 5th June 2004, 10:16   #9
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Hey Shantanu,
Thats a good point u made there. Again from my indycar and nascar experience, lol, them being only computer games here, tire pressure and toe angles very much effect the handling. Never used to understand what the toe angles could do to the car. Used to try different settings. You just made it clearer now. Back to nascar with a vengeance.
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Old 5th June 2004, 11:07   #10
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Well this is getting way too technical for me to take part in (though me being the best car setup guy in my group in GranTurismo3 game) ..
Anyway, as u guys said the setup of a car (camber/toe/tyrepressure/downforce/diff-setup etc etc etc) all play an important role.. But in the end it is upto the Driver. Even the car set up only for optimum understeer can be set into a drifto-steer by a pro-driver..
Though as ported said "besides hatchbacks are very tail-happy" is because the weight distribution of a hatchback is generally more heavier towards the front.. And thats precisely what is needed for a FWD car to oversteer. While entering the corner at a slightly higher-speed than usual, u have to lift off the accelarator for the car to lose it's tail (coz then the weight is transferred to the front and the rear lifts off), but then it is totally on control of accelerator/opposite steering lock/Left foot braking etc etc.. otherwise either u'll end up losing the tail completely and spinning OR going straight where your nose is pointed. .. Ofcourse this being my personal experience.. so may not work with everyone, as driving styles of every individual is different.
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Old 5th June 2004, 11:43   #11
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uh....er.....was thinking maybe we could talk abt understeer and oversteer in the cars most of drive here in India.
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Old 5th June 2004, 14:18   #12
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This is one of those things that everyone knows, but finds hard to put down on paper (or in this case, the monitor!) clearly. Lemme give it a shot. However, its hard to really explain the CAUSE of either oversteer (OS) or understeer (US) without really going into details of a particular car. There's no simple answer Tom!

Definitions:
US: also known as "push", is when a car doesn't turn as quickly as the angle of the front wheels i.e. An understeering vehicle wants to point to the outside of a turn, no matter where the wheels are actually pointing. This is the WORST thing a racer can have on a track, but its the BEST thing for a normal driver on the road!

OS: or "loose" is when the vehicles' back end slides around. An oversteering vehicle feels like it's about to spin, and will spin if the driver isn't skilled enough to catch it. On the track this is prefered over understeer, but still not the ideal setup. However, in front wheel drive cars, teams tend to set up a car to oversteer a bit as this helps then in turning, keeping the front wheels straight, and allowing them to put the power down harder and faster.

There are a lot of different dynamics that cause under- or oversteer; the front-to-rear weight bias of the car is the most influential, the stiffness of the anti-roll bars, which wheels are doing the work of accelerating the car (front or rear)

Putting a roll bar (or sway bar depending on what you call it) on one end of the car will tend to give the opposite end of the car more traction. Thus, most cars come equipped fromt he factory with a front bar but none in the rear, in order to induce safe understeer in a car. I say "safe" because to stop a car understeering, all you have to do is lift off the throttle, which is the most natural instinct for your average driver.

If they lift off in an oversteering car, well, I guess they'll be getting a closer look at the tree on the side of the road!

I found the best table I have seens for expalining how suspension set-up and tyre pressure affects th balance of a car. Check it out here...this really should explain everything CLEARLY!

Understeer/Oversteer Table

Hope that helped.

Rtech
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Old 5th June 2004, 14:36   #13
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Rtech...that was a really good explanation. Thanks a lot man...appreciate ur effort!
So while racing, dirvers prefer to set up the car for more oversteer than understeer....right?
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Old 5th June 2004, 16:25   #14
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Really good rtech. I do want my car to oversteer on most occasions coz its just plain fun. The problem i face in racing with this is that a lot of speed is lost getting the car back in a straight line again so the guy behind me gets close. I found a lot is said about the steering activity and at what angle one takes the corners. Outside then into the bend and out again. This helps me keep the speed without letting the car do a ballet manouver on the road. I have drawn a "Rough Diagram" to illustrate this.
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Old 5th June 2004, 16:38   #15
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SO how do u get a front wheel drive car to slide the rear on a corner?
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