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Going around 85mph on a curve on the free way. The max speed limit is 50mph for this overpath curve, suddenly the back wheels lost control and my car fishtailed about 3 times and luckly I regain control over the car. For a moment there I thought I just lost 35G. The funny thing was that my safty wasn't my biggest concern.

I've driven this road with the same speed or more for years in my prelude and nothing like this has ever happen before. Could it be the difference between FWD and RWD?

Do any of you know whats the best way to regain control of you car in this kind of situation? FYI, trac control was on. And it was scary as hell..

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Originally posted by 6days:

Could it be the difference between FWD and RWD?


Probably. I think you should learn how to countersteer. And if you are countersteering, don't hit the brakes because then your tires will bite and you will snap the other way.


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By making this post I am not claiming to be an expert of any sort on the topic and should not be taken as such. It's just my opinion and worth what you paid for it.
 

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Must have been some oil or water on the road. I find it hard to belive that you broke lose on dry and level pavement at only 35 over the limit
.

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What tires were you running? I've broken loose before.
 

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Do you know what precipitated the fishtailing? Did you come off the gas or apply the brakes in the middle of the curve? Doing either of these things will transfer the weight from the rear wheels to the front wheels, decreasing the grip of the rear wheels and resulting in your tail coming out. Was it rainy or could there have been oil on the road?

To avoid this in the future, when you're at or near the limit of adhesion on a curve, don't come off the throttle and don't brake. If your tail does come out (this is called oversteer), steer in the direction of the skid to correct (but be ready to correct in the other direction as your car could snap the other way around) and perhaps apply a little gas to transfer weight back to the rear tires. Easier said than done of course. My suggestion would be for you to take a driving course where they have specially prepared skid cars to help you learn how to control both understeer and oversteer situations.

Finally, yes, this is one of the big differences between RWD and FWD. RWD is more prone to oversteer (the tail coming out), while FWD is more prone to understeer (the car not turning in as much as you would like), which is easier and more natural to control (you just turn the wheel more and come off the gas). RWD, though, is a heck of a lot more fun.



[This message has been edited by Young (edited November 14, 2000).]
 

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Discussion Starter #6
Bluebyu.. The road was dry and level pavement

Sophie... I got the good year eagles and you?

young.... I think your right. I took my foot off the gas and probaly thats what caused it. Thank for your suggestion.

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I used to (well still anyway) induce a bit of oversteer on my 2k GTS by abruptly lifting off the gas -- makes the back end come around real fast. I love the way that feels.

And today, I just did that on my IS... the front end definitely feels heavier, but the rear end will snap given the right motivation. I find it easier to tap the brakes with my left foot to get things going, but still, nothing beats the exhilerating feel of a heel-toe 5-3 downshift without clutching (that's if I can get it juuuust right).

On a related note, do you find shifting with the e-shift while turning (or when under- or oversteering) a little hard? One, I find my hand reaching down to shift, and second, I lose where the buttons are and I end up misshifting.
 

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You can also change the alignment settings if you don't want to upgrade the suspension. But, yeah, the bottom line is that a suspension upgrade will allow you to customize the settings if you so desire.
 

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I had to get used to RWD again after driving FWD luxury cars for 8 years when I got my LS400. It takes a little getting used to at first, it is a very different feeling when the car starts to get unsettled. Just takes time to learn the intricacies of your car.

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A simple way to dial in some understeer is to put more air in the rear tires. Conversely, if you want more oversteer (for autocross, say), put more air in the front than in the rear.

We've been talking about trailing throttle oversteer here, but there's also something called power oversteer. You can induce power oversteer in a RWD car by stomping hard on the gas in the middle of curve while you're at the limit of adhesion. The fast spinning of the rear wheels make them lose all of their cornering traction and the rear end comes out.

In summary, for a RWD car:

1. Decelerating in a corner induces oversteer (trailing throttle oversteer)

2. Accelerating gradually in a corner induces _understeer_

3. Accelerating abruptly and hard in a corner induces oversteer (power oversteer)
 

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Young, I thought it is the other way around for the tire pressure setup, or am I just confused here? I thought you stiffen the rear to induce oversteer and stiffen the front to induce understeer?
 

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It seems counterintuitive to me as well, but this is what I was told by a Toyo tire rep (and he was a helluva driver) and by an experienced autocrosser. And it does jive with normal manufacturer recommendation...higher pressures in back. The manufacturer wants you to have the safer settings...the understeer settings.

Could somone explain the physics of tire pressures?
 

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To correct oversteer the rear tire pressures should be raised. To correct understeer the front tire pressures should be raised. It *does* seem counter intuitive doesn't it? I would think that lowering rear tire pressure would increase rear tire grip therefore reducing understeer. But I think it works the other way for some reason...anyone care to explain?

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By making this post I am not claiming to be an expert of any sort on the topic and should not be taken as such. It's just my opinion and worth what you paid for it.
 

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Some stuff that might help to explain...maybe
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Oversteer is when the rear wheels are carving a larger arc than the front wheels or the intended line of the turn. Rear "slip angles" exceed those of the front tires. This is often described as a "loose" condition, as the car feels like it may swap ends, or be "twitchy."

This condition can be caused by "power oversteer", where you need to reduce power in order to bring the back end back into line.
Understeer is when the front wheels are carving a larger arc than the rear wheels. This is often described as "push" or "pushing" - as the front end feels like it is plowing off of a corner.

Further acceleration only compounds the push, as weight shifts back to the rear drive wheels off of the front turning wheels, leading to a further lessening of the car's ability to turn in.

Understeer can be remedied by slight modulation in throttle to transfer weight forward to the front wheels, aiding their traction and ability to carve the turn.

Many cars are designed to have a tendency to understeer. If the driver gets uncomfortable and "lifts" off the gas, that will cause the front end to tighten the curve - a relatively safer, and more predictable condition.
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UNDERSTEER
In a constant radius turn, when the slip angle of the front tires is greater than the slip angle of the rear tires the car will understeer as speed increases. A race car driver will say the car 'has a push' or 'is tight'. (Most production cars are designed with mild understeer, the rationale being that street cars driven by distracted drivers will move away from on-coming traffic to the outside of the road.)

From behind the wheel, a driver senses understeer when the car is running wider than steering input, and increasing the steering angle does not make the front end turn in. This means the front tires need more download to generate more grip. To transfer weight to the front means giving up the acceleration you just worked so hard to achieve. Reduced cornering speed means reduced corner exit speed, and a loss of rpm's all the way down the next straight, or driving off the road!!!

Determine the problem. Test for understeer
Tape the top of the steering wheel when the wheels are pointing straight. Note how much steering angle is used through a given corner at a moderate speed. If there is more steering input with increased speed, the car is pushing. Determine if what seems like exit oversteer is really the car's reaction to too much steering input through the corner because of tight entry.

OVERSTEER
In a constant radius turn, when the slip angle at the rear tires is greater than the slip angle of the front tires the car will oversteer as speed increases. A race car driver will say the car 'is loose'.

From the drivers seat, when you recognize that the front of the car is turned too far into the apex, you are sensing that the car is going into oversteer. Your first reaction should be to dial in opposite lock, steering into the direction that the rear is moving. Then settle the rear by adding a little throttle. When you lift off the throttle, weight shifts from the rear to the front, reducing rear tire adhesion. This is commonly known as 'trailing throttle oversteer'. With just a slight lift, the driver can help the car rotate into a smooth transition to oversteer; with too abrupt a lift the car will snap into a spin.

DRIVER INFLUENCES
The driver influences tire loading by throttle application. Adding throttle transfers load on to the rear, giving additional grip for acceleration, but reducing grip for cornering. With a gradual application of throttle understeer will result. Remember smoothness. Too abrupt on the throttle will throw the car into oversteer.

THE CAR
What we are looking for in car set-up is balance. If you are doing a lot of steering, something is wrong. Start soft - soft tire pressures, soft springs, soft shock - so you
 

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Originally posted by Young:
Interesting read. Where's that from?
All from my own head! I sat here and typed out the whole thing! ~cough~ Hehe.
Actually, every long line of ------------------------- is a different site. I want all U guys to know that pressing Ctrl+C and then Ctrl+V is very tedious work!




[This message has been edited by HIBBoyScott (edited November 15, 2000).]
 
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