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GP Bikes => Suggestions and wishlist => Topic started by: Fightone on May 27, 2017, 11:51:56 am

Title: Front tyre incorrect slip angle
Post by: Fightone on May 27, 2017, 11:51:56 am
Hello Piboso,

I hope you read this topic. This is the thing I felt wrong for a long time playing GP Bikes so I finally decided to post it here.

The issue is: I found that the front tyre has unrealistic slip angle profile what causes the bike understreer on the corner entry more than the real one. The issue is not with the tyre grip itself, which is ok but just with the slip angle profile (i.e. slip angle at which this max grip is generated).
To be exact: maximum grip of the front tyre is reached at a bit too high slip angles comparing to the rear tyre (while in real life difference in slip angles beetween front and rear is at least not that big).
It can even be noticed when you just look at some replay and notice that the front wheel is visually drifting along the track a bit unrealisticly like it's "shifting sideways" a bit on the corner exit when you pick up a bike - that's also this problem.
The issue should be related to some general game settings cause it's noticed on all bikes more or less and I haven't found anything related to tyre slip angles in the bike folders.

Unfortunatly I can't say exactly "how much" the angle profile is wrong because it's up to the feel but now it's too far off for sure. But ofc I'd be able to tell the right one if there'r a chance to play with it a bit and I'm ready to give that feedback.

I believe fixing it would improve real feel of bikes in the game and front of the bike will feel more "planted" to the group.
P.S. Folks, please don't jump into discussion if you don't know the exact physics I'm talking about.
P.S.S. If you have an idea where this setting can be hidded in the game files - you'r welcome.  :)
Title: Re: Front tyre incorrect slip angle
Post by: h106frp on May 27, 2017, 01:50:35 pm
The .tyre file has the values you are looking for
Title: Re: Front tyre incorrect slip angle
Post by: Fightone on May 27, 2017, 02:21:18 pm
Can you point out where exactly? I don't see anything related to slip angles there.
Title: Re: Front tyre incorrect slip angle
Post by: h106frp on May 27, 2017, 03:06:05 pm
The values relate to the pacejka tyre model values so you will need to do some detective work. MAX posted a tool to help a bit
http://forum.piboso.com/index.php?topic=1920.0 (http://forum.piboso.com/index.php?topic=1920.0)

It works like this
http://www.racer.nl/reference/pacejka.htm (http://www.racer.nl/reference/pacejka.htm)
Title: Re: Front tyre incorrect slip angle
Post by: Fightone on May 27, 2017, 07:58:25 pm
Thanks! That's good stuff. Will try it out.
Title: Re: Front tyre incorrect slip angle
Post by: HornetMaX on May 27, 2017, 08:56:35 pm
Quote from: Fightone on May 27, 2017, 02:21:18 pm
Quote from: h106frp on May 27, 2017, 03:06:05 pm
Quote from: Fightone on May 27, 2017, 11:51:56 am
P.S. Folks, please don't jump into discussion if you don't know the exact physics I'm talking about.

The values relate to the pacejka tyre model values so you will need to do some detective work. MAX posted a tool to help a bit
http://forum.piboso.com/index.php?topic=1920.0 (http://forum.piboso.com/index.php?topic=1920.0)

It works like this
http://www.racer.nl/reference/pacejka.htm (http://www.racer.nl/reference/pacejka.htm)

Can you point out where exactly? I don't see anything related to slip angles there.

That's what I call getting off to a bad start ...

Anyway, the "front drifting" problem has been discussed a lot in the past, it's unlikely one can fix it by tampering with the tyre model (.tyre). It seems to be "baked" in the current physics.




Title: Re: Front tyre incorrect slip angle
Post by: Fightone on May 29, 2017, 10:17:20 am
Well, I'll try and let you know if that works. Yet, I don't see a reason why adjusting slip angles won't help, it think it should.  :)
"That's what I call getting off to a bad start ..."
Why? I'm not an expert in this particular game and any simulation model, just I'm not interested in getting into phys. discussion with people who don't know how slip angles work and how they relate to real bike behaviour (it's a bit complicated in fact), that's why I wrote this.
Title: Re: Front tyre incorrect slip angle
Post by: BOBR6 84 on May 29, 2017, 12:46:44 pm
MaX is the gpbikes resident, helpful genius!

The issue you posted about does need sorting out though.. I remember piboso saying it is a physics limitation.. Not sure what that means but doesnt sound good  :(
Title: Re: Front tyre incorrect slip angle
Post by: HornetMaX on May 29, 2017, 01:39:12 pm
Quote from: Fightone on May 29, 2017, 10:17:20 am
Well, I'll try and let you know if that works. Yet, I don't see a reason why adjusting slip angles won't help, it think it should.  :)
"That's what I call getting off to a bad start ..."
Why? I'm not an expert in this particular game and any simulation model, just I'm not interested in getting into phys. discussion with people who don't know how slip angles work and how they relate to real bike behaviour (it's a bit complicated in fact), that's why I wrote this.

It just seemed funny that you ask  people without the necessary knowledge to stay out of the discussion but then, once pointed to the physics file you're a bit lost (and you state you're not interested to get into the physics).

There's no sucha thing as "adjusting slip angles". It's not as easy as "find the parameter responsible of the relationship between grip and slip angle, modify it and we're done".

If it was that easy, it would have been done already by one of the many modders that have played with this stuff.
It may even be the root cause of the unexpected behavior is not even in the tyre modelling ...

Quote from: BOBR6 84 on May 29, 2017, 12:46:44 pm
MaX is the gpbikes resident, helpful genius!

I'm less and less resident and never been a genius. But thanks :)
Title: Re: Front tyre incorrect slip angle
Post by: Fightone on May 29, 2017, 05:51:51 pm
Quote from: HornetMaX on May 29, 2017, 01:39:12 pm
Quote from: Fightone on May 29, 2017, 10:17:20 am
Well, I'll try and let you know if that works. Yet, I don't see a reason why adjusting slip angles won't help, it think it should.  :)
"That's what I call getting off to a bad start ..."
Why? I'm not an expert in this particular game and any simulation model, just I'm not interested in getting into phys. discussion with people who don't know how slip angles work and how they relate to real bike behaviour (it's a bit complicated in fact), that's why I wrote this.

It just seemed funny that you ask  people without the necessary knowledge to stay out of the discussion but then, once pointed to the physics file you're a bit lost (and you state you're not interested to get into the physics).

No offence Max but you'r reading me somehow wrong. There's a difference between physics and physics simulation in computer games. So I'm pretty decent at first and not so good at second. So nothing controversial.
Quote from: HornetMaX on May 29, 2017, 01:39:12 pm
There's no sucha thing as "adjusting slip angles". It's not as easy as "find the parameter responsible of the relationship between grip and slip angle, modify it and we're done".

Will reply you when I finally get to play with these values.

Title: Re: Front tyre incorrect slip angle
Post by: CapeDoctor on May 30, 2017, 06:48:17 am
Quote from: Fightone on May 29, 2017, 05:51:51 pm

Will reply you when I finally get to play with these values.



lol, mate, admire the enthusiasm, at least.
maybe best no-one here shatters your dream of finding this value, so we should wait in anticipation of your discoveries.  ;D
Title: Re: Front tyre incorrect slip angle
Post by: HornetMaX on May 30, 2017, 07:10:59 am
No dream-shattering. If he's a basic understanding of physics he should have no trouble in getting how the tyre model works.

Side note: I think the link posted by h106frp (racer.nl) has a simplified model, the one used in GPB (and WRS, KRP) is described in Pacejka's book (Tyre and vehicle dynamics).
Still good to read throught the racer.nl stuff though, to get the overall idea.
Title: Re: Front tyre incorrect slip angle
Post by: Fightone on June 01, 2017, 02:30:54 pm
Hello folks.
I'm back with some results. There's no surprises :D it didn't work out but I have at least a few notes:
- there's no problem to adjust slip angle profile of the tyre, it can easily be done by altering p_Dy1 and p_Cy1 values with help of Max's tool, everything else is pretty much just a fine tuning.
- game doesn't really react to changes like it should. When you lowering peak slip angle the grip level also goes down for some unknown reason so if you set peak slip angle close to 0 - you will get grip level close to 0 as well what doesn't make any sense physically-wise. It can be compensated ofc with setting insanely high level of grip in the same tyre file (i used 15) but that just shows that there's some problem with physics engine.
- front wheel drift remains even with slip angles set ~ 0 (and grip level set to 15..) what proves that the phys engine doesn't work like it should as slip angle in the tyre profile obviously doesn't correspond with one in the game. I also tried to compensate front wheel drift by increasing rear wheel slip but it also doesn't work like it should i.e. something in bike behaviour changes (wobbling tendency, grip level etc) but not the real slip angle which remains the same.

So as a conclusion: some raw physics issue, can't be fixed by slip angles adjustments.

That's it. Any comments are welcome now. :)
Title: Re: Front tyre incorrect slip angle
Post by: HornetMaX on June 01, 2017, 02:52:23 pm
Quote from: Fightone on June 01, 2017, 02:30:54 pm
- game doesn't really react to changes like it should. When you lowering peak slip angle the grip level also goes down for some unknown reason so if you set peak slip angle close to 0 - you will get grip level close to 0 as well what doesn't make any sense physically-wise.

I'm not sure what you mean with "if you set peak slip angle close to 0". Can you post the diagrams that come out of my tool and show what you think it's unexpected ?
Title: Re: Front tyre incorrect slip angle
Post by: PiBoSo on June 01, 2017, 03:03:34 pm
Quote from: Fightone on June 01, 2017, 02:30:54 pm
Hello folks.
I'm back with some results. There's no surprises :D it didn't work out but I have at least a few notes:
- there's no problem to adjust slip angle profile of the tyre, it can easily be done by altering p_Dy1 and p_Cy1 values with help of Max's tool, everything else is pretty much just a fine tuning.
- game doesn't really react to changes like it should. When you lowering peak slip angle the grip level also goes down for some unknown reason so if you set peak slip angle close to 0 - you will get grip level close to 0 as well what doesn't make any sense physically-wise. It can be compensated ofc with setting insanely high level of grip in the same tyre file (i used 15) but that just shows that there's some problem with physics engine.
- front wheel drift remains even with slip angles set ~ 0 (and grip level set to 15..) what proves that the phys engine doesn't work like it should as slip angle in the tyre profile obviously doesn't correspond with one in the game. I also tried to compensate front wheel drift by increasing rear wheel slip but it also doesn't work like it should i.e. something in bike behaviour changes (wobbling tendency, grip level etc) but not the real slip angle which remains the same.

So as a conclusion: some raw physics issue, can't be fixed by slip angles adjustments.

That's it. Any comments are welcome now. :)


Changing p_Dy1 directly changes the grip.
To change the lateral stiffness without lowering the grip you have to play with p_Cy1 and p_Ky1 only.
Title: Re: Front tyre incorrect slip angle
Post by: Fightone on June 01, 2017, 03:29:31 pm
Quote from: HornetMaX on June 01, 2017, 02:52:23 pm
Quote from: Fightone on June 01, 2017, 02:30:54 pm
- game doesn't really react to changes like it should. When you lowering peak slip angle the grip level also goes down for some unknown reason so if you set peak slip angle close to 0 - you will get grip level close to 0 as well what doesn't make any sense physically-wise.

I'm not sure what you mean with "if you set peak slip angle close to 0". Can you post the diagrams that come out of my tool and show what you think it's unexpected ?
Meaning that max lateral force is reached at ~<3 degrees of slip angle or so, not 15-20. I'll send you diagrams a bit later.
Quote from: PiBoSo on June 01, 2017, 03:03:34 pm
Changing p_Dy1 directly changes the grip.
To change the lateral stiffness without lowering the grip you have to play with p_Cy1 and p_Ky1 only.

Thanks! Maybe I missed something but it seemed to me that maximum lat. force remained the same in the Max's tool while I was altering that parameter. I'll recheck and let you know.
Title: Re: Front tyre incorrect slip angle
Post by: Fightone on June 01, 2017, 08:41:05 pm
2Max: attaching the diagram.(http://savepic.ru/14255548.png)
2Piboso - thanks for the advice! My bad here, indeed I didn't notice that p_Dy1 was influencing general grip.
So with p_k1 value I can play with max slip angles and it works!

The only problem remaining is that it's still not enough to overcome "fron tire slipping issue" i.e. even setting slip angle close to 0 doesn't demolish slipping of the front tyre. And compensating it with rear wheel slipping requires setting unrealistic values so the bikes starts behaving weird, so it's not a solution. So still, the issue is incorporated somewhere in the physics engine, not in tyres..

Title: Re: Front tyre incorrect slip angle
Post by: HornetMaX on June 01, 2017, 08:43:17 pm
Quote from: Fightone on June 01, 2017, 08:41:05 pm
2Max: attaching the diagram.

It's not attached but no longer really needed anyway: I got what you tried to do and yeah, using p_Dy1 was not the right way, as explained by PiBoSo.

EDIT: it just appeared.

Quote from: Fightone on June 01, 2017, 08:41:05 pm
The only problem remaining is that it's still not enough to overcome "fron tire slipping issue" i.e. even setting slip angle close to 0 doesn't demolish slipping of the front tyre. And compensating it with rear wheel sleeping requires setting unrealistic values so the bikes starts behaving weird, so it's not a solution. So still, the issue is incorporated somewhere in the physics engine, not in tyres..

:)
Title: Re: Front tyre incorrect slip angle
Post by: Fightone on June 01, 2017, 08:49:18 pm
Yea, I added it a "second" after the post) showing the last setup I tried, but yeah.. it's not really needed anymore after I made sure myself that the issue is not in tyres specification. :)
Title: Re: Front tyre incorrect slip angle
Post by: CapeDoctor on June 02, 2017, 08:01:22 am
hey guys
been following this thread, and i wanted to ask something which may or may not be related.
not being sure about slip angles and such, i'll try and convey it in layman rookie terms, and hopefully the more physics savvy guys will know what i'm on about.
so, again, in this case, the bike that this happens most to me with is the RGV250, but that could just be because it's the bike i ride most, currently.
so what sometimes happens is, i'm feeling the front tire 'biting' nicely under braking into a corner, pretty low lean, and now i'm exiting the corner, slowly lifting the bike and accelerating out - i can feel the tire gripping nicely on the bottom side of the tire.
then, instead of gripping more onto the main tread of the tire as i try to lift and accelerate at the same time, it seems to start gripping more and more up the side of the tire, so that if i keep accelerating, it just 'bites' back down on the SIDE of the tire and causes the front to tuck in.(BITE in, more like)  ;D
this does NOT happen very often, but it has happened enough times for me to ask about it.
is this something that could happen in reality? i've not had the 'nads to try this sort of high speed low lean cornering in reality much, lol... it just doesn't seem right, though....
anyway, hope i've explained it okay, and after all that, i hope it's somehow related to this thread.
if not, well, apologies in advance. i'll move this to a new thread if needed. ;)
Title: Re: Front tyre incorrect slip angle
Post by: Fightone on June 02, 2017, 08:47:02 am
Quote from: CapeDoctor on June 02, 2017, 08:01:22 am
i can feel the tire gripping nicely on the bottom side of the tire.
then, instead of gripping more onto the main tread of the tire as i try to lift and accelerate at the same time, it seems to start gripping more and more up the side of the tire, so that if i keep accelerating, it just 'bites' back down on the SIDE of the tire and causes the front to tuck in.(BITE in, more like)  ;D

To be honest I don't quite understand the concept of "bottom" and "side" of the tire in your explanation. I mean: part of the tire gripping the ground depends on the lean angle so how side of the tyre can start gripping more if you'r lifting the bike out of the corner? I'm confused.  :)
Title: Re: Front tyre incorrect slip angle
Post by: CapeDoctor on June 02, 2017, 09:39:50 am
yes, it's kind of hard to explain, and it has me confused as well, which is why i'm asking about it.

maybe this diagram can help a bit more:
(http://www.motorcyclecruiser.com/sites/motorcyclecruiser.com/files/styles/large_1x_/public/tirechartnew-web.jpg?itok=tR9TjUfg&fc=50,50)

so when i talk about the 'bottom' i'm talking about the actual tread part of the tire, in this pic the section covered with 'A'
when i say the side, i really mean it starts to grip more towards the 'B' section in the diagram, and if i accelerate, this gets worse and the tire basically just pulls me to the ground with sheer grip.
as if the section of the tire that's gripping is literally crawling up the side of the tire as i accelerate..... so, from A to B and BEYOND....
it doesn't happen often - REPEAT - it does not happen often.
when it does, though, i'm talking HEAVY gripping situations with the mad 2 stroke power-band.
and i have to back off the throttle in what should otherwise be the perfect time to be ON the throttle.

Title: Re: Front tyre incorrect slip angle
Post by: HornetMaX on June 02, 2017, 09:55:52 am
Quote from: CapeDoctor on June 02, 2017, 09:39:50 am
so when i talk about the 'bottom' i'm talking about the actual tread part of the tire, in this pic the section covered with 'A'

GPB has no notion of part A (bottom) and part B (side): the tire profile is round (circle arc).
Title: Re: Front tyre incorrect slip angle
Post by: CapeDoctor on June 02, 2017, 10:14:30 am
Max, so by that reckoning, then what is happening to me in this situation is correct?
am i just asking too much grip at too low/high an angle...?

         :)
Title: Re: Front tyre incorrect slip angle
Post by: Fightone on June 02, 2017, 10:31:31 am
Quote from: CapeDoctor on June 02, 2017, 10:14:30 am
Max, so by that reckoning, then what is happening to me in this situation is correct?
am i just asking too much grip at too low/high an angle...?

         :)

Eventhough, I still don't fully understand what's happening I can tell you that what you describe sounds strange. In fact, front wheel never ever can wash away after you already started accelerating (that's possible only in the very first moment of opening the trottle on max lean angle, because of the front tyre instant unload).When you are already acelerating our of the corner - only rear tire can slip away.

Now a question for me: how can a front tyre crawl on the side if you'r picking up the bike? How can this happen geometrically-wise? I don't understand how can a front tyre start gripping in the B section if the section itself is fully determined by the lean agle, that's what's bugging me in your explanation. :)
Title: Re: Front tyre incorrect slip angle
Post by: CapeDoctor on June 02, 2017, 11:37:04 am
Fightone, mate, the thing that's bugging you about my explanation is the very same thing that's bugging me, as i don't believe this should ever happen in reality, just as you say. however, it does happen to me on occasion and i find it very strange.
that's the whole reason for my post.
so, the same thing is bugging us both there, lol

i can make a replay of it, but a replay is not going to give you the feel  of what is happening, so that's useless.
and it definitely feels like the grip is actually forcing me over, it doesn't feel like a front washout.
i suffer plenty of those, and they are normal (well, if you ride that way, of course)
this is a complete different feeling - and what makes it difficult is that it has caused me to crash each time it happens.
you can think for yourself - you're leaned far over coming out of a corner, and you basically HAVE to accelerate, otherwise the bike will fall over.
and when this happens, if i accelerate, the bike will also fall over because the grip is pulling me down on the side.
so, i'm screwed either way - back off or fall over, accelerate or fall over.
each options results in falling over.
again, though - i want to remind everyone reading this - it does NOT happen very often at all.
i'd say, 3 or 4 times of 100.
and so far, only with my preferred ride - RGV250.
possibly with another bike, but i'm not really sure about that.... 
Title: Re: Front tyre incorrect slip angle
Post by: Fightone on June 02, 2017, 11:51:20 am
Quote from: CapeDoctor on June 02, 2017, 11:37:04 am
i can make a replay of it, but a replay is not going to give you the feel  of what is happening, so that's useless.
and it definitely feels like the grip is actually forcing me over, it doesn't feel like a front washout.

Please make one if you can, I'm very good at looking at replays..) Just beetter make 2: tank view and outside (auto).
+
Quote from: CapeDoctor on June 02, 2017, 11:37:04 am
and it definitely feels like the grip is actually forcing me over, it doesn't feel like a front washout.

Does this sudden grip force your front out or inside the turn?
Title: Re: Front tyre incorrect slip angle
Post by: HornetMaX on June 02, 2017, 11:54:44 am
Quote from: CapeDoctor on June 02, 2017, 10:14:30 am
Max, so by that reckoning, then what is happening to me in this situation is correct?
am i just asking too much grip at too low/high an angle...?

Hard to say. Losing the front exiting is a bit unusual.
We know the virtual rider sometimes over-reacts when the front slides and steers more into the turn trying to lift the bike (and hence making things worse ,losing the front completely).
If you have a video or replay maybe ...
Title: Re: Front tyre incorrect slip angle
Post by: CapeDoctor on June 02, 2017, 12:06:22 pm
okay, i'll do a replay next time it happens, but as i mentioned already, a replay won't give you the feel of what the bike is doing as the rider.
most likely, it'll look like a regular washout in a replay, but who knows - there may be some clue to an experienced eye.
you should at least see that i am accelerating when this happens...
as you say, it's not like i'm actually 'losing' the front, but more like the part of the tire that is gripping is literally forcing me over.
as i accelerate, so the grip increases AND starts to pull me over quicker.
okay, for sure a replay of the next time ;)
Title: Re: Front tyre incorrect slip angle
Post by: Vini on June 02, 2017, 01:01:03 pm
i think i know exactly what you mean and it's hard to demonstrate with a replay.
if you ride very long sweeping lines with no brake or throttle at max lean (lorenzo/250 style), eventually there comes a point of no return (on some bikes and tracks) where you know that you are doomed and that there is no way to get the bike up again. all that happens before you even get a hint of actual feedback (chatter) from the front.

the only thing that saves me sometimes (apart from simply chosing a different, less smooth line or, worst case, not going max lean angle) is to go into the corner with very low rider lean. when i reach that point i lean the rider all the way and this often makes the bike stand up just enough to avoid the front washout.

this is of course very bad for two-strokes because the lack of engine brake requires these kind of lines.
Title: Re: Front tyre incorrect slip angle
Post by: Stout Johnson on June 02, 2017, 06:54:48 pm
I think we are talking many different things now here.
Title: Re: Front tyre incorrect slip angle
Post by: Fightone on June 02, 2017, 08:00:28 pm
Quote from: Stout Johnson on June 02, 2017, 06:54:48 pm
But I am not sure whether this is a good title for the behaviour, as I doubt that there is actual front wheel slip happening. What we see is the front wheel somehow being dragged unrealistically which in reality would have translate to front wheel slip. But in GPB I assume it is rather a visual/geometry/resultant force bug which causes it to look like front wheel slip.

You are right, that's something we already figured out here. I'm also not sure if real slipping is happening or not in the game engine, but its definitely not related to slip angles being defined by the tyre spec.
Anyway, I called the topic like that because visual position of the bike in relation to the surface IRL is determined exactly by front to rear slip angles relation, that's why "unrealistic front wheel slip" was the first logical assumtion.
Title: Re: Front tyre incorrect slip angle
Post by: HornetMaX on June 03, 2017, 12:24:06 pm
Quote from: Fightone on June 02, 2017, 08:00:28 pm
I'm also not sure if real slipping is happening or not in the game engine

You're gonna make somebody angry with that :)
Of course real slipping happens in the game engine: when they tyre diagram (force vs long slip or lat slip) crosses the origin, that means that if the tyre is not slipping it is not generating any force.
As in GPB you're able to take turns and to accelerate from stop, slipping is happening :)

Quote from: Fightone on June 02, 2017, 08:00:28 pm
but its definitely not related to slip angles being defined by the tyre spec.

Not sure what you mean with "slip angles being defined by the tyre spec": the tyre model does not define a "slip angle".
Also, what my tool show are the diagrams in pure longitudinal (i.e. no side slip) and pure lateral (i.e. no longitudinal slip). In real conditions you normally have both at the same time (and the maximum force is somehow shared between the two components).
Title: Re: Front tyre incorrect slip angle
Post by: Fightone on June 03, 2017, 01:16:27 pm
Quote from: HornetMaX on June 03, 2017, 12:24:06 pm
You're gonna make somebody angry with that :)
Of course real slipping happens in the game engine: when they tyre diagram (force vs long slip or lat slip) crosses the origin, that means that if the tyre is not slipping it is not generating any force.
As in GPB you're able to take turns and to accelerate from stop, slipping is happening :)

Thanks cap, I agree  :)
Quote from: HornetMaX on June 03, 2017, 12:24:06 pm
Also, what my tool show are the diagrams in pure longitudinal (i.e. no side slip) and pure lateral (i.e. no longitudinal slip). In real conditions you normally have both at the same time (and the maximum force is somehow shared between the two components).

I double that.
Quote from: HornetMaX on June 03, 2017, 12:24:06 pm
with "slip angles being defined by the tyre spec": the tyre model does not define a "slip angle".

well, it does in a way. Of course in collaboration with other factors i.e. what the bike is doing on the road etc but lets not argue over nothing.
Most importantly, tyre model is something that should define a max slip angle that could be reached with that tyre and that's not happening with GP Bikes.
What I meant when I say that, is that I'm not sure if this "unrealistic dragging of the front tyre" is caused by slip angle being calculated in the phys. engine (because as noted by Stout Johnson it indeed doesn't look like regular slipping or the tyre) or it is just some "game magic" overlayed on physics and causing this dragging. Anyway it's very wrong and remains a problem.

So as the bottom line: I don't doubt that slipping is modelled in the phys. engine, that's something that I checked first hand while playing with tyre characteristics. I doubt that this weird slipping is the same kind of slipping as "normal one" happening because of the tyre flex, while generating force.
Title: Re: Front tyre incorrect slip angle
Post by: HornetMaX on June 03, 2017, 04:20:41 pm
Quote from: Fightone on June 03, 2017, 01:16:27 pm
So as the bottom line: I don't doubt that slipping is modelled in the phys. engine, that's something that I checked first hand while playing with tyre characteristics. I doubt that this weird slipping is the same kind of slipping as "normal one" happening because of the tyre flex, while generating force.

OK then, we're set.

But ... slipping happens because of tyre flex  ?! :o
Title: Re: Front tyre incorrect slip angle
Post by: Hawk on June 03, 2017, 04:44:34 pm
As I understand the theory, a tyre is slipping all the time it's in motion, whether under acceleration or not?

Hawk.
Title: Re: Front tyre incorrect slip angle
Post by: Fightone on June 03, 2017, 05:00:01 pm
Quote from: HornetMaX on June 03, 2017, 04:20:41 pm
But ... slipping happens because of tyre flex  ?! :o

Slipping as "slipping friction" - no, it's a physical process when friction surfaces are moving in relation to each other while in contact.
Slipping of the tyre - as a physical phenomena when rotation direction of the tire (not a deam vector :D, but where the wheel is "pointed") is not matching direction of its headway motion - yes, I can say that it's caused by tire flex, cause otherwise peak slip angle would tend to 0 while stiffness of the wheel tends to infinity (if we take regular rubber static/slipping frinction values).
So if it weren't for tyre flex - there would be effectively no slip angle while going around the track fast "i.e. having maximum out of the tyre".
Quote from: Hawk on June 03, 2017, 04:44:34 pm
As I understand the theory, a tyre is slipping all the time it's in motion, whether under acceleration or not?

Hawk.

Correct. To be exact: it's always slipping while producing force, not just in motion.
Title: Re: Front tyre incorrect slip angle
Post by: Become dust on June 03, 2017, 05:16:09 pm
I wonder if this discussion would interest Piboso? or perhaps many similar discussion threads has been created before.

even both i bet
Title: Re: Front tyre incorrect slip angle
Post by: Fightone on June 03, 2017, 05:21:15 pm
Quote from: Become dust on June 03, 2017, 05:16:09 pm
I wonder if this discussion would interest Piboso?

I hope so. Not the whole discussion but at least the bug we are talking about. Vehicle behaviour is imho the most important thing for a simulator so I guess a lot of people would appreciate that fix (eventhough they might not realize what's exactly the problem while playing GP Bikes, but they should definitely feel the improvement).
Title: Re: Front tyre incorrect slip angle
Post by: HornetMaX on June 03, 2017, 05:46:54 pm
Quote from: Fightone on June 03, 2017, 05:00:01 pm
Slipping as "slipping friction" - no, it's a physical process when friction surfaces are moving in relation to each other while in contact.
Slipping of the tyre - as a physical phenomena when rotation direction of the tire (not a deam vector :D, but where the wheel is "pointed") is not matching direction of its headway motion - yes, I can say that it's caused by tire flex, cause otherwise peak slip angle would tend to 0 while stiffness of the wheel tends to infinity (if we take regular rubber static/slipping frinction values).
So if it weren't for tyre flex - there would be effectively no slip angle while going around the track fast "i.e. having maximum out of the tyre".

I disagree. Slipping, longitudinally or laterally, does not happen because of tyre flex. You can slip with a perfectly rigid "tyre".

Quote from: Fightone on June 03, 2017, 05:00:01 pm
Quote from: Hawk on June 03, 2017, 04:44:34 pm
As I understand the theory, a tyre is slipping all the time it's in motion, whether under acceleration or not?

Correct. To be exact: it's always slipping while producing force, not just in motion.

So in fact it's not correct: it's slipping if it is generating force. Ideally it could be in motion (constant speed and direction) without any slip.

The problem is that most people thinks of "slipping" as in extreme cases (e.g. locking while braking or doing a burn standing still).
In fact, when accelerating mildly to move from 90Khm to 100Khm, your rear tyre is generating a force and hence slipping a bit.
Fore example, it could be that the tyre forward velocity (the velocity of the tyre axle) is 95 Kmh while the velocity of the contact patch relative to the ground is 97 Kmh: it is slipping, even if a naked eye won't detect it (nor the rider on the bike).
Title: Re: Front tyre incorrect slip angle
Post by: Fightone on June 03, 2017, 06:06:19 pm
Quote from: HornetMaX on June 03, 2017, 05:46:54 pm
Quote from: Fightone on June 03, 2017, 05:00:01 pm
Slipping as "slipping friction" - no, it's a physical process when friction surfaces are moving in relation to each other while in contact.
Slipping of the tyre - as a physical phenomena when rotation direction of the tire (not a deam vector :D, but where the wheel is "pointed") is not matching direction of its headway motion - yes, I can say that it's caused by tire flex, cause otherwise peak slip angle would tend to 0 while stiffness of the wheel tends to infinity (if we take regular rubber static/slipping frinction values).
So if it weren't for tyre flex - there would be effectively no slip angle while going around the track fast "i.e. having maximum out of the tyre".

I disagree. Slipping, longitudinally or laterally, does not happen because of tyre flex. You can slip with a perfectly rigid "tyre".

You should notice that I'm talking about "peak slip angle" and "maximum performance out of the tyre". I'm not talking about any possible slip, that's obvious.. Type of physics that I'm trying to discuss here is "racing-wise" not just "any slip of anything anywhere".
Quote from: HornetMaX on June 03, 2017, 05:46:54 pm
Quote from: Fightone on June 03, 2017, 05:00:01 pm
Correct. To be exact: it's always slipping while producing force, not just in motion.

So in fact it's not correct: it's slipping if it is generating force. Ideally it could be in motion (constant speed and direction) without any slip.

You said incorrect and just repeated what I wrote. :)

P.S. Anyhow, I long lost the taste for fights over physics, that's what I've been doing for years in the past so if you want recognition - I subscribe to your latest explanations about tyre dynamics. :) They are accurate.

What I'm really interested here - is only fixing the issue in the game that's obvious to all of us.
Title: Re: Front tyre incorrect slip angle
Post by: HornetMaX on June 03, 2017, 06:13:07 pm
Quote from: Fightone on June 03, 2017, 06:06:19 pm
You should notice that I'm talking about "peak slip angle" and "maximum performance out of the tyre". I'm not talking about any possible slip, that's obvious.. Type of physics that I'm trying to discuss here is "racing-wise" not just "any slip of anything anywhere".

So you mean that with a rigid tyre the peak slip angle is zero ? :o

Or maybe by "peak slip angle" you mean "the smallest slip angle at which the tyre generates the maximum force over all possible slip angles" ?
Which would be a pretty unusual definition of "peak" ...

Quote from: Fightone on June 03, 2017, 06:06:19 pm
Quote from: HornetMaX on June 03, 2017, 05:46:54 pm
Quote from: Fightone on June 03, 2017, 05:00:01 pm
Correct. To be exact: it's always slipping while producing force, not just in motion.

So in fact it's not correct: it's slipping if it is generating force. Ideally it could be in motion (constant speed and direction) without any slip.

You said incorrect and just repeated what I wrote. :)

Because you told Hawk he was correct before adding something that, in facts, says he was wrong (thing on which I agree).
Title: Re: Front tyre incorrect slip angle
Post by: Fightone on June 03, 2017, 06:21:34 pm
Quote from: HornetMaX on June 03, 2017, 06:13:07 pm
Quote from: Fightone on June 03, 2017, 06:06:19 pm
You should notice that I'm talking about "peak slip angle" and "maximum performance out of the tyre". I'm not talking about any possible slip, that's obvious.. Type of physics that I'm trying to discuss here is "racing-wise" not just "any slip of anything anywhere".

So you mean that with a rigid tyre the peak slip angle is zero ? :o

No I mean that:
Quote from: Fightone on June 03, 2017, 05:00:01 pm
peak slip angle would tend to 0 while stiffness of the wheel tends to infinity (if we take regular rubber static/slipping frinction values).

no more no less. It's tending to 0 only with regular rubber friction coeffs but not necessarily for others materials.
Quote from: HornetMaX on June 03, 2017, 06:13:07 pm
Or maybe by "peak slip angle" you mean "the smallest slip angle at which the tyre generates the maximum force over all possible slip angles" ?
Which would be a pretty unusual definition of "peak" ...

No I meant "slip angle when tyre generates max lat force".
Quote from: HornetMaX on June 03, 2017, 06:13:07 pm
Because you told Hawk he was correct before adding something that, in facts, says he was wrong (thing on which I agree).

Maan.. ye, lets just finish it. :)


Title: Re: Front tyre incorrect slip angle
Post by: CapeDoctor on June 21, 2017, 08:03:59 am
hi guys
for what it's worth, i got a short replay where this front end issue i suffer with the RGV250 happens.
in the replay, you can see i am on my line, past the apex and starting to lift the bike and accelerate. as i accelerate, it looks like the front wheel turns in to the right.
i can assure you, i am NOT turning it in, it is the acceleration that is making it happen. i am essentially not steering here, simply letting the bike lift naturally with minimal input. adding throttle just forces it over to the side, and this makes no sense.
well, there's a short replay you can watch and judge for yourselves. maybe i am doing something inherently wrong here, but please remember, it doesn't happen that often - which makes it all the more frustrating when it does, lol.
replay: https://www.mediafire.com/?3wnbrz7ppkrjdt7

p.s: best way to watch the replay clip is to use the 'Free' cam., and rotate around so that you are looking at the front of the bike, then watch the clip. this is probably the easiest way to see what's happening. ;)
Title: Re: Front tyre incorrect slip angle
Post by: HornetMaX on June 21, 2017, 05:36:46 pm
@CapeDoc: downloaded the file, extracted fine, but when I put it in the right GPB folder, GPB doesn't see it (it sees my other replay files). Weird  :o
Title: Re: Front tyre incorrect slip angle
Post by: CapeDoctor on June 21, 2017, 08:02:29 pm
hmm...that is weird.
let me think on that a while....  :)
Title: Re: Front tyre incorrect slip angle
Post by: Fightone on June 22, 2017, 07:16:24 pm
Interestingely enough, I can see the reply but it's empty i.e. I see black screen when clicking to some bike attached cameras. But prolly I just don't have this bike. I think fraps + youtube is the best idea here.  :)
Title: Re: Front tyre incorrect slip angle
Post by: LOOPATELI on June 22, 2017, 11:53:33 pm
better if you upload a private video on youtube and post it here
Title: Re: Front tyre incorrect slip angle
Post by: CapeDoctor on June 23, 2017, 02:02:27 pm
sure, i can make a video clip (i use bandicam, much nicer than fraps, imo)
the only drawback is that you won't be able to 'investigate' it properly via the replay cams, slo-mo, etc.
in essence, what you'll see is me coming through a right-hand corner, the second-last corner of A1 Ring /Red Bull Ring, +- 130km/h.
i am past the apex and begin lifting the bike, and i also start to accelerate - i mean, it'd be silly not to, lol - then, what you see from outside, is that the front wheel turns in to the right as i accelerate, and tips me over. it looks as if i am pushing the bars to the right, but i can assure you i am not, it is the acceleration that is literally 'dragging' the tire back down.
the crazy thing is i can take the corner in pretty much the same way, and most times the doesn't happen.
okay, i'll find some time over the weekend to post up a clip to my YT account ;)
Title: Re: Front tyre incorrect slip angle
Post by: HornetMaX on June 23, 2017, 02:27:14 pm
Would be nice to see why the replay doesn't work though. It is supposed to just work ....
Title: Re: Front tyre incorrect slip angle
Post by: CapeDoctor on June 23, 2017, 06:31:31 pm
i wonder if it might be due to me fiddling with the bike settings in BikeEd?

what i did was, i opened the bike in BikeEd (first time using it),  and adjusted the little light blue cross a little that i assumed represents the rider's eye view-point. it seemed to make a little difference in-game, and i made no other changes.
other than that, i can't think of any reason it won't work.