Quote from roadrash17 :

Momentum isn't a force, it's a conserved quantity.

http://dictionary.reference.com/browse/centrifugal+force

Look at the second reference. It states it's a fictitious force. i.e. it's something we think is there but actually isn't. I have a college level physics book that states what I am telling you. Centrifugal force is something someone came up with to describe the feeling of being pushed outwards when going in a circle. The actual reason you feel like you're being pushed outwards is explained in Newtons First law of Motion: Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. That external force is the force of friction between the tires and the road.



There is a limit of how fast you can go around a corner with a car. you will never be able to fully eliminate understeer, but you can do your best to increase the top cornering speed of a car. I suggest playing with Camber, tire pressure, and anti-roll.




The thing people call centrifugal force (actually Momentum, a conserved quantity) acts on all bodies in motion.



The suspension is helping the car go around the corner by taking a portion of the kinetic energy (also a conserved quantity) that the car has and dissipating it by compressing the shocks on the outside side of the car as it corners. The acceleration vector does point towards the center of the circle and the fictitious force is, in fact, centrifugal force.

I've done my best to explain this concept to you...it's something that took weeks of schooling to fully comprehend to a point where I could use it and explain it to people. I hope I helped.

I know this is a fictitious force, as I've mentioned before. It is actually the momentum in circular motions. So we have basically the same concepts, correct me if I'm wrong.

Last edited by pajkul, Sun, 5 Jun 2011 19:36.

"The higher load on the front tyres will make the front stiffness relatively less (cornering stiffness increases non-proprortionally with load), thus creating understeer on turn in."

Meaning this? I can't really understand this sentence.:

Anyway, I'm pretty much sure that the momentum (momentum is a fictitious force used in non-inertial reference frames) you wrote about is the centrifugal force. I read about it in some car magazines and web articles written by allegedly smart people. So we have two different opinions, can anyone go into facts?

Quote from roadrash17 :

The force that causes the tires to slip isn't a force, but it's called momentum. Momentum describes a moving objects desire to resist a change in direction. When you drive, the car and everything inside the car has momentum. When you turn, the car WANTs to continue in it's straight path but the force of friction between the tires and the road, if high enough, causes the car to turn, but because of its desire to resist change in direction, the car leans and you feel like there is a force pushing you towards the outside of the corner when there isn't. That feeling is what people like to think of as centrifugal force. Now, if momentum is too great, then the tires break the force of traction and you slide. Better?

Yes, thanks. Can you tell me why is it so hard to eliminate understeer? The front is just slightly heavier than the rear of the car. Even if I set the anti roll to the extreme values, it doesn't help that much.
Just to add one thing: when the car is finally taking the turn, the only grip it has is through its tyres, so the centrifugal force exerts on the car just as on a person sitting inside the car. But the suspension is dimnishing the real effect it has on the car's stablitiy. Am I right? In described case, there is the acceleration vector pointed towards the center of the circle being the path the car drives. So the fictitious force is the centrifugal force.

Quote from Ingolf :

No, it doesn't.
But there is a centripital force.

http://en.wikipedia.org/wiki/Centrifugal_force

It does. In non-inertial reference frames, e.g. from the car perspective.

Quote from roadrash17 :

Mmk. To start off:
-there is no such thing as centrifugal force.

Now that I've told you that, lets get down to business:

Understeer is caused by something called momentum. When you enter a corner with too much speed, the momentum of your car is "breaking" friction and causing the car to slide straight in the corner. The key to proper cornering is limited body roll. The key to limiting body roll is a stiff chassis. Body roll causes weight shifts which disrupt the line that the car was taking. However, from my understanding, a slight amount of weight transfer onto the front tires does help because it increases the force of friction. Hence why if you understeer, you can recover, or at least attempt to, by pressing the gas and brake at the same time. That transfers enough weight to the drive tires so they can "pull" you out of the understeer. And it really does work, I've tried it. lol

Anywho, feel free to roast me. I used my understanding of physics (I'm in school to be a mechanical engineer) to attempt to answer his question.

Why is it that there's no centrifugal force? In general sense of physics, this force exists. And I'm convinced this is one of the forces the car has to deal with when turning. From the car's perspective, this force is trying to beak the friction between the tyres and the road. If the loses grip, it means that there was some higher force pointed against the friction (how do I call this force)? Probably fictitious force, in this case - centrifugal force.

That's what I was afraid of, but no, this is not topic related.

What's more: when I drive RWD with very heavy rear and lock the tyre by braking in the corner, when I turn right, the one blocked is the front right. Even if the brake balance is set to 50%. This means that the load on rear tyres is higher making them more difficult to lock. No matter how many times higher is the centrifugal force generated on the rear of the car, the maximum friction should rise the same number of times, as it depends on the gravity force. I don't get it.

Last edited by pajkul, Sat, 4 Jun 2011 18:23.

Hello everybody,
I was trying to understand the very physical sense of most of the FWD cars being prone to understeer, but some things are getting too far.

http://www.suv-rollovers.com/a ... tions/understeer-01292010

According to this website:

A front-heavy vehicle with low rear roll stiffness (from soft springing and/or undersized or nonexistent rear anti-roll bars) will have a tendency to terminal understeer: its front tires, being more heavily loaded even in the static condition, will reach the limits of their adhesion before the rear tires, and thus will develop larger slip angles. Front-wheel drive cars are also prone to understeer because not only are they usually front-heavy, transmitting power through the front wheels also reduces their grip available for cornering.

To make things less complicated, let's talk about the car not accelerating or braking at all, just entering the corner. I've thought the higher the load on the front tires, the higher the grip. As it turns out, somebody forgot to mention (in my opinion) the important suspension settings factor.

In FXO, for example, the weight distribution is as follows: 57 front, 43 rear. When the car is turning right, the weight is going to the left more to the front of the car than, as the centrifugal force is higher, but at the same time the maximum friction the front can generate is higher than on the rear. We all know that when this max. friction is e.g. two times higher when the centrifugal force is two times higher. To prevent mentioned weight transfer, I set minimum anti roll on the rear and the maximum in the front. 57F and 43R on the paper doesn't seem to make a very big difference, however the car is still very understeery, as the first wheels losing grip are the front ones. Can anyone get me through this?

My bet is as follows:

The physics update won't be released before October 2011.

Why hasn't it been released yet? The answer is quite simple. Releasing a version changing everything in the game physics means erasing all the results on lfsworld.net. Any current WR will be gone for ever, and there's no way they can fix some bugs in the car physics after releasing the update. The car behaviour has to be perfectly predictable, there's no space for some inappropriate results of equations embedded in the physics model.

Thanks, now I understand the problem.

The fictitioue force is turned to the opposite direction to the movement of the wheel. If the fictitious force is turned to the right, then the wheel rotates to the left, thus counter clockwise. I have no idea what is not clear in my explaination.

I'd say the wheel rotates counter clockwise. The tyre surface on the left is substantially thinner than on the right side, and considering the fact there's also fictitious force involved caused by the accelerating movement of the wheel that makes the tyre thicker on the right side, the answer is B.
When wheel accelerates, every point of the wheel wants to stay where it was before acceleration, that's why there's more rubber on the right.