Yeah, it might have one, but it sure feels like it's not there. That's beside the point though, really. Even my wife will occationally spin the inside front with normal driving.

Quote from Bandit77 :

if you want to be a smart-ass, then tell me why the LACK of centripetal force doesn't lift my wheels when bolting down a straight...

the lack of a force moves something... that's interesting, really.

Reattend your physics course.

To turn (move in a NOT straight line) reguires a force. If that force is not strong enough you will not turn enough. A turning car recieves that force from the friction between the road surface and the tyres. Because the contact patch between the tyres and road is lower than the COG (centre of gravity) of the car the friction force creates a torque force that results in making the car lean.

For a vehicle (or any particle) to travel in a straight line the sum of all lateral forces must be zero. Otherwise the path will be curved.


A easy and safe test to figure this out is:
You need a clear table (one that is not cluttered with junk).
A piece of paper (A4 size or similar, not glossy).
A top heavy plastic cup or other similar nonbreaking piece of equipment that has its COG high.

Put the piece of paper on the table. Put the topheavy cup on it.
Now yank the paper from under the topheavy cup.
Notice in which direction the cup falls. It falls to the opposite direction from the one you pulled the paper to. How is this possible?
The reason is the same as when a car leans in a turn.
Torque.

Disclaimer: Simplified explanation that does not take the suspensions roll center into account. And when I'm talking about torque I don't mean the engines torque.

Quote from Ball Bearing Turbo :

Look at the G meter when you're getting wheelspin in LFS. LOOK at it.

Then think to yourself "Bandit77, with a car pulling a G or so, A) how much weight is acting on the inside tire, even including the spring, and B) how much torque am I attempting to transfer through said tire?".

done that. when doing the "turn in to a street" thing with way less than 50 kph, only 0.5 G's (sideways) with 0.2 G's are needed to rev it up like mad. ha, hilarious.

in faster corners you will need 0.6 G's - most obviously because you don't accelerate that hard.

and that's with a XFG with a setup as stiff as you wouldn't have in a production car. softer setups make it worse - see UF1.

hmmm... I really do think I've driven thru one or two bends IRL with that g-load and had no spin (and most of all reving-up) like that.

and I think that swift chasing the f40 in the video does a couple of turns above 0.5 G, too. now isn't the XFG said to be very close to the swift?

case closed for me. thanks for the hint.

Quote from atledreier :

but I guess 380Nm to the front will do that to any tire. But the passat needs alot more torque to actually break the tire free. So bandit, maybe you have a very good suspension setup combined with not too much torque. That would describe your situation.

first of all, the engine-torque at the shaft doesn't have a direct impact on the wheels at all. just as sidenote. let's just keep it simple: the passat sure has more balls.

well, I can't really complain about the suspension of my present car, but I've driven a of other FWDs, stiffer and softer, more and less powerful than mine. same thing: you might get different degrees of powerundersteer, but hitting the rev-limiter? no way, maybe on slippery surfaces but then the other wheel spins too.

but yeah, the last possibility would be that there wasn't one single car among them that was sh!tty enough to act like an XFG.

Quote from Shotglass :

it just occured to me that in lfs maybe the open diffs are just a tad too open too idealised

what I'm saying. that's most probably why the FXO with the standard LSD setting comes closer to a reallife open diff.
now actually, the initial question is still not answered: will this be fixed or neglected as it's underused anyway.

Quote from March Hare :

...

not that your essay isn't correct - but I think you missed the point (or may I say punchline) in that little side-argument.

I miss a lot of things. Especially apexes.

Quote from March Hare :

I miss a lot of things. Especially apexes.

nice one

Quote from Bandit77 :

done that. when doing the "turn in to a street" thing with way less than 50 kph, only 0.5 G's (sideways) with 0.2 G's are needed to rev it up like mad. ha, hilarious.

in faster corners you will need 0.6 G's - most obviously because you don't accelerate that hard.

The vast majority of road driving is done at under 0.3gs.

You need to take into account that LFS cars are infinitely stiff and will not flex at all like a RL car, then that any LFS racing setup is far far stiffer than you'd run in a road car and due to the bumpy nature of real tracks far stiffer than your likely to run IRL in a production car. Then take into account that most setups are still designed for locked diff exploits, as Android pointed out they have to lift a wheel to work. I think LFS's tire scrubbing/slipping sounds maybe slightly exaggerated still, so that'll make you more aware of what's going on. Lastly your driving the thing far harder than IRL.

Until you have an accurately setup car you can't even start to analysis the diffs anyway.

There is not one thing to be fixed (eg understeer in FWD)… tire model needs to be excelled in general. Also suspension and chassis flex… (it is more likely that we wont see chassis flex ever in LFS)
There is nothing completely wrong that lfs’s engine is simulating now… it may be a bit overdone in some ways but not completely wrong…
Also to prevent front wheel spin you do not need only a hard setup in general but higher or a lot higher rear roll resistance that in front.
Do you mind sharing the setups you used while testing the wheelspin behavior?

One of my friends happen to own a 93 swift GTI and I know it spins it's front tires like crazy...

Chassis flex an modern cars (from what I've read) generally never exceeds a half a degree, even during the most extreme cirumstances, so it's affect seems pretty minimal on monocoque design cars.

Quote from Bob Smith :

The vast majority of road driving is done at under 0.3gs.

I wouldn't doubt this a second.

By the way, Bob, far off topic but I have to say this: I LOVE your "road going" setups. Gave me a good starting point for making a drivable LX-setup.

Quote from ajp71 :

You need to take into account that LFS cars are infinitely stiff and will not flex at all like a RL car, then that any LFS racing setup is far far stiffer than you'd run in a road car and due to the bumpy nature of real tracks far stiffer than your likely to run IRL in a production car. Then take into account that most setups are still designed for locked diff exploits, as Android pointed out they have to lift a wheel to work. I think LFS's tire scrubbing/slipping sounds maybe slightly exaggerated still, so that'll make you more aware of what's going on. Lastly your driving the thing far harder than IRL.

Until you have an accurately setup car you can't even start to analysis the diffs anyway.

So this means a softer setup might reduce this nasty effect? In my understanding this is right unless the car dives to much on the rear. This however would mean you need to have a soft suspension in the front an a relatively stiff one in the back, which is definitely not production car style.

Quote from kaynd :

There is not one thing to be fixed (eg understeer in FWD)… tire model needs to be excelled in general. Also suspension and chassis flex… (it is more likely that we wont see chassis flex ever in LFS)
There is nothing completely wrong that lfs’s engine is simulating now… it may be a bit overdone in some ways but not completely wrong…
Also to prevent front wheel spin you do not need only a hard setup in general but higher or a lot higher rear roll resistance that in front.
Do you mind sharing the setups you used while testing the wheelspin behavior?

I'll get a setup for you. But you don't even need it because the UF1's standard set is kind of illustration enough.

I'm a suspension-softy , and curing the (IMHO) exaggerated diff behavior means stiffen up the rear to an unsound level.

Quote :

One of my friends happen to own a 93 swift GTI and I know it spins it's front tires like crazy...

I just did some turns with my car about half an hour ago, and yes, it is possible, but you have to hit the throttle like an idiot and even then it's not as nasty as it is in LFS. So basically it's my well trained right foot that has prevented my inner front wheel from spinning for all these years , but IF I floor it, the effect isn't nearly as aggravating as in LFS.

So in the end, the wheelspin-thing is overpresent (couldn't find a better word). If it's because of the diff (which I believe) or any other shortcomings is probably not detectable for us.

I mean, if I can't say the diff is crap because I don't know if the causes lie elsewhere, how can you say it's accurate without nowing if all the rest that affects this phenomena is sorted out?


hmm... damn long post considering the fact that for me this case is closed... hehehe.

Quote from Bandit77 :

if you want to be a smart-ass, then tell me why the LACK of centripetal force doesn't lift my wheels when bolting down a straight...

Sorry, but I don't understand. In a straight line there is no force to lift your wheels, and the rest of the car isn't turning either....

Quote from Bandit77 :

the lack of a force moves something... that's interesting, really.

You know when you go round a corner, and your shopping falls over? That's a LACK of cornering force on your shopping. Your car goes round the corner, but your shopping wants to continue in a straight line - it can't, so it falls over. Same with leaning to the outside and pressing against your door cards, or the load in your car as the car turns - things WANT to carry on in a straight line. So, ultimately, it is a lack of force that causes body roll, and the body roll (combined with complex interactions in the suspension, chassis etc) causes a tyre to lift up. Simple.

Go back to physics school (primary school level) and they'll teach you this.[/quote]

Quote from tristancliffe :

You know when you go round a corner, and your shopping falls over? That's a LACK of cornering force on your shopping.

in the second place.
if there's no force attacking the shopping, the a LACK of another force can't make them fall over.

Quote :

but your shopping wants to continue in a straight line - it can't, so it falls over.

that comes first. THIS force causes the shopping to fall over.

Quote :

Go back to physics school (primary school level) and they'll teach you this.

will you accompany me? they might even tell you that building a house shouldn't be started with tayloring the roof.

Quote :

Sorry, but I don't understand. In a straight ...

Maybe you do now.

Quote from Bandit77 :

in the second place.
if there's no force attacking the shopping, the a LACK of another force can't make them fall over.
...
that comes first. THIS force causes the shopping to fall over.

So then, what force causes the shopping to fall over? Please describe the force acting on it, causing it to fall over (other than gravity). I'll even make a space for your description:

.
.
.
.

The problem is that there isn't any (or rather enough) force acting on it to cause it to follow the path of the cart. Therefore it's a lack of force acting on it in relation to the cart, and it falls over.

The diff thing is one thing, but this argument is cementing your stupidity quite nicely.

Quote from Ball Bearing Turbo :

...

if you think you're right and I'm wrong - f. it! I don't care.
if you think you've won an argument because I won't answer to this anymore - so be it. I don't care. I don't feel bad because of this... but I hope it makes you feel better.

I don't win anything by convincing you, so f. it again. If you want to just ignore the core issues of what I'm saying - be my guest. It just shows that there's no point in talking / writing to you.

Quote from tristancliffe :

You know when you go round a corner, and your shopping falls over? That's a LACK of cornering force on your shopping. Your car goes round the corner, but your shopping wants to continue in a straight line - it can't, so it falls over. Same with leaning to the outside and pressing against your door cards, or the load in your car as the car turns - things WANT to carry on in a straight line. So, ultimately, it is a lack of force that causes body roll, and the body roll (combined with complex interactions in the suspension, chassis etc) causes a tyre to lift up. Simple.

but why would you look at the forces acting on the car from a stationary observers pov instead of coordinates attached to the car?

Me skips the force/physics/whatever/highiq argument.
So basically the lack of (slight as was stated before) chassis flex it's the problem of the high understeer of lfs on tarmac? How it could be improved?
And most of all how it could be improved leaving unaltered the current behaviour of lfs on mud/gravel?
Because i think lfs feels almost perfect in the fwd understeer department on slippery surfaces.

Quote from Shotglass :

but why would you look at the forces acting on the car from a stationary observers pov instead of coordinates attached to the car?

There isn't any difference.
Except for notation. Untill you reach the speeds that require relativity to be taken into account.

Bandit77, you sure know your physics.

Quote from Rubenz81 :

So basically the lack of (slight as was stated before) chassis flex it's the problem of the high understeer of lfs on tarmac? How it could be improved?

No, chassis flex on its own will it make it even worse.
Now the granit rigid chassis gives the ability to utilitize the full potential of your suspension setup.
I think it is more about the tire model that will improve any kind of unnatural behaviour.
Anyway I don't think that there is extreme under steer now on the FWD cars... you can do pretty match whatever you want, regarding the vehicles basic characteristics, with a proper setup.
It is normal for a front weighted car to be generally understeery...

Quote from March Hare :

There isn't any difference.

Well, one is an inertial reference frame, the other is not.

Quote from w126 :

Well, one is an inertial reference frame, the other is not.

Our planet is orbiting the Sun. Our solar system is orbiting the center of the Milkyway. Our galaxy is whizzing through space at a mindboggling speed. But it all depends on how accurate you want to be.

The fact of the matter is that there is no force acting on the car to "throw it off the track". And your shopping that toples over because of your driving. Is not acted upon by some arbitrary fictional force. It is just trying to keep going straight when it's surroundings are taking a curved path. The reason it toples over and doesn't slam into your door, is the friction between it and the seat.

Another exaple of the same phenomena (WYSINWYG) is when you hit a a wall with a car. The car stops but you keep going untill the seatbelts/steeringwheel/wall stops you. Same for the Firstaid kit on your parcelshelf. There is no WallForce the drag it forward. It's the LACK of a stopping force that makes it fly forward. Untill, ofcourse, it hits the back of your head. Then it is acted upon by a force and slows down.

Quote from March Hare :

There isn't any difference.
Except for notation. Untill you reach the speeds that require relativity to be taken into account.

yes there is since in the static frame will have centripetal forces and inertia acting on everything that isnt bolted to the car whereas in the car frame youll suddenly find centrifugal forces acting on everything

Yes the sign(+ -) changes to make the equations look nicer and lead people to misunderstand physics.

But the facts don't.

Choosing the right inertial frame of reference can make the sun orbit the earth. Do you think that is a fact? Or just a misinterpretation?

Quote from Bandit77 :

So this means a softer setup might reduce this nasty effect? In my understanding this is right unless the car dives to much on the rear. This however would mean you need to have a soft suspension in the front an a relatively stiff one in the back, which is definitely not production car style.

No a correctly setup car in a non-rigid body physics model is what you need, unfortunately no bodies managed to make a sufficiently detailed real time program to do this task and I can't see it happening in the near future either.

Quote from kaynd :

...

Thanks, by the way i too think LFS understeer isnt a "dramatic"
problem but i think also Bandit77 has it's own reason.
Still i dont feel it like a huge problem, just something a little bit "exaggerated" by LFS physics model and that only on tarmac... but who i am to judge tarmac racing? Everybody know only sissies drive on tarmac real man drive on gravel (joking )

Quote from March Hare :

Choosing the right inertial frame of reference can make the sun orbit the earth. Do you think that is a fact? Or just a misinterpretation?

neither ... dont mistake modeling something for figuring out how the "machine" behind it really works