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December 04, 2020, 02:33:21 PM

Preload

Started by Desteban, March 27, 2014, 04:26:58 PM

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Desteban

Hey I have been playing with suspension for a long time now and am still a little lost at this point:

If I increase preload does it lift my bike? If so then I would have less sag, right?
But I noticed a bit preload on the rear is more stable under braking, because it feels my rear won't come of the ground so fast.
Therefore I thought increasing the preload reduces the supension travel and gives more sag. But I read everywhere differently so I wanted to ask what the value does ingame.

BOBR6 84

If you increase preload you will have less ''static'' sag!

Try working on the rebound and compression settings more!

I doubt its possible to work out the suspension setup in relation to how heavy the rider is..

That would be good to have custom riders with different hight, weight, and riding style!

BOBR6 84

I have lots of ''front end'' trouble on gpbikes. Not so much with braking but with turning and holding a line! On some corners/tracks the bike is trying to turn but something is stopping it?

This happens alot on brands hatch! The front end doesnt track properly around corners..

Is this a setup issue? Or a general gpbikes issue on modded tracks etc?


C21

In my opinion it´s caused by modded tracks.
If you don´t have troubles at Victoria....
# Member of the CAWS Racing Team #


HornetMaX

More preload means you'll need a greater force to obtain the same compression of the rear shock absorber.
This means that more preload = less static sag as said, but it has other implications too (e.g. less squat).
Also, more preload = less extension available to follow the road when passing over a hole.

@BOBR6 74: some custom tracks have irregularities that do not play well with GPB physics. As suggested by C21, try to see if you have the same issue on Victoria.

MaX.

Hawk

April 09, 2014, 09:33:31 AM #5 Last Edit: April 09, 2014, 09:35:13 AM by Hawk_UK
Quote from: C21 on April 09, 2014, 08:38:07 AM
In my opinion it´s caused by modded tracks.
If you don´t have troubles at Victoria....

I absolutely agree C21.

I've looked at several max files of modded tracks that have obviously been ripped, and the track surface topology is terrible, especially on tight hairpin bends.

Maybe Piboso can confirm this, but the collision model is calculated from the surfaces of the mesh(Usually is I beleive?)
Well, if this is so, then if the surface mesh topology is chaotic and a lot of surface edges are so close to each other on corners that you couldn't fit a piece of paper in the space between some edges then I think this is what causes these problems with the collision model?
Don't know if I'm exactly right, but I think I'm on the right track with why there are grip and weird handling problems on certain corners.

I've not had a chance to look at the Victoria model mesh, so I cannot really comment, but I have notice that the Victoria track is pretty reliable for bike handling and performance. though on occasions their does seem to be a small problem with weird things happening on the 3rd bend from the end of the lap(Not sure what the corner is called, but it's the sharp right hand turn at the bottom of the hill.) :)

C21

[OT]
I ususally develop bike physics on Victoria and did that quite satisfying (imho  ;D ).
As i turned to test on other tracks i was very disappointed.
Weird things happened on Brno (before the GP resurfacing) and other tracks....(before resurfacing most of the modded tracks were a pain to drive on (only my personal view on this!))

I returned to Victoria and the bike handled as suggested, making fun to drive (e.g. SC59 , Moto3,..) and getting a "realistic" feedback.
Victoria still has the crash issue on corner 10 down Lucky Heights but that´s most an issue with the 125cc and smaller bikes.....in my opinion it´s also caused by a bad track model...in reality there are not much crashs on that particular corner.
# Member of the CAWS Racing Team #


C21

QuoteIf I increase preload does it lift my bike? If so then I would have less sag, right?
Yes./ Yes.

QuoteTherefore I thought increasing the preload reduces the supension travel and gives more sag
No.
Increasing the preload did not reduce the travel. It has no effect on the travel in terms of maximum travel value. It changes the ratio of positiv to negativ suspension travel. Changing the preload changes the initial position of the suspension.
Increasing the preload results in:
- lift of front and/or rear (increase in ground clearance)
- less sag
- decrease of negativ suspension travel.
# Member of the CAWS Racing Team #


BOBR6 84

Yes the circuits I have the least trouble with are victoria, brno gp, paul ricard.

They seem to be the most reliable for me.. Although sometimes I have trouble going over lukey hights on victoria circuit! (the hill)
Depending how I enter the corner sometimes the front end doesnt find the grip. Almost like its dragging itself back inline?

I had trouble with the sharp right hand turn at the bottom of lukey hights but more so on beta3!

Thats why I asked about adjustable steering dampers in a previous post because on some slow turns the handlebars shake alot and it usually drops the bike!

I dont know if that would make a difference or if it is just the track surface etc like u guys say?

Hawk

Quote from: BOBR6 84 on April 09, 2014, 09:15:59 PM
Yes the circuits I have the least trouble with are victoria, brno gp, paul ricard.

They seem to be the most reliable for me.. Although sometimes I have trouble going over lukey hights on victoria circuit! (the hill)
Depending how I enter the corner sometimes the front end doesnt find the grip. Almost like its dragging itself back inline?

I had trouble with the sharp right hand turn at the bottom of lukey hights but more so on beta3!

Thats why I asked about adjustable steering dampers in a previous post because on some slow turns the handlebars shake alot and it usually drops the bike!

I dont know if that would make a difference or if it is just the track surface etc like u guys say?

Yeah.... Since I started riding in cockpit view, I also noticed the rider shaking the handlebars a lot, even on the straights, but particularly in certain corners even though not traveling fast.
I can only presume it is to do with the reaction to collision detections that have been calculated from badly modelled track surfaces. I hope Piboso can comment on this as it would be interesting to find out if this can happen because of bad modelling topology on the track surface and resultant collision detections?

Klax75

The shaking handles, for me, using full manual lean. If I put the ride behind the wind screen and not hanging off the bike it goes away. So I just have to reposition my rider then I can take the corner.

Desteban

The shaking handle bars often tell me there is a setup issue. Most of the time it is fixable when you play with the rebound on the fork.

Hey about the preload I think Maxhud can prove that preload reduces the ride height. Gonna upload some pics once I have Internet again.

C21

QuoteThats why I asked about adjustable steering dampers in a previous post because on some slow turns the handlebars shake alot and it usually drops the bike!
That´s not a steering damper issue. It´s caused by bad modelled track surface.
I had this on another track (i can´t remember the name) when i was testing and got handle bar shaking and fork travelling in a weird manner on a slow corner. It was so terrible that i quit testing on that track. I had this issue on that one only....so i say: It´s the track, not the bike  ;)

QuoteI have trouble going over lukey hights on victoria circuit! (the hill)
Depending how I enter the corner sometimes the front end doesnt find the grip. Almost like its dragging itself back inline?
That´s a normal behavior on that track. You can easy loose the front closing throttle near the apex of that corner because you will "overload" the front with that action and the weight distribution from rear (under accleration) to front (close throttle). That´s close to real....

QuoteI had trouble with the sharp right hand turn at the bottom of lukey hights but more so on beta3!
That´s still an issue and it´s caused imho by an incorrect track model comparing real layout to ingame layout. Imho the corner falls to much into the right....

QuoteHey about the preload I think Maxhud can prove that preload reduces the ride height. Gonna upload some pics once I have Internet again.
If you decrease the preload it will decrease the ride height, increasing will increase the right hide.
# Member of the CAWS Racing Team #


Desteban

Quote from: C21 on April 10, 2014, 06:34:23 AM
QuoteHey about the preload I think Maxhud can prove that preload reduces the ride height. Gonna upload some pics once I have Internet again.
If you decrease the preload it will decrease the ride height, increasing will increase the right hide.

In real life that is, according to max hud and the feeling I get during a ride 0 Preload is the max height and the max value of preload is the lowest height. You can test it yourself though, take a bike max the preload value and drop the bike in the pits. Then you can see the difference.

HornetMaX

Quote from: Desteban on April 10, 2014, 04:50:07 PM
Quote from: C21 on April 10, 2014, 06:34:23 AM
QuoteHey about the preload I think Maxhud can prove that preload reduces the ride height. Gonna upload some pics once I have Internet again.
If you decrease the preload it will decrease the ride height, increasing will increase the right hide.

In real life that is, according to max hud and the feeling I get during a ride 0 Preload is the max height and the max value of preload is the lowest height. You can test it yourself though, take a bike max the preload value and drop the bike in the pits. Then you can see the difference.
Hmm, can you document this with a couple of screenshots ? It sounds strange to me.

On a side note, I've been thinking for a while to have some sort of indication of the "ride height", but I've concluded that this shouold be shown by Piboso in the garage, as this measure is only available in the pits in real life, with the bike standing still.


Concerning the "shaking handlebars": it's very very hard to explain where it comes from without knowing the GPB internals. It's not even sure (at least to me) if it's something that comes from the bike model or from the "virtual rider".

One thing I can say is this: the GPB "virtual rider" is essentially a dynamic controller that tries to "invert" the motorbike physics. "invert" means that the "virtual rider" computes the physics inputs (e.g. steering torque) to obtain a certain set of outputs (e.g. lean angle), while the bike model does the opposite, it computes the outputs from the inputs.

Dynamic controllers based on model inversion are often very sensible to differences between the assumed model (the one inverted) and the real model (the real one GPB uses). In presence of uncertainties, model errors or approximations, the controller may have some weird behavior and in some cases it can generate large oscillating inputs in order to stabilize the closed loop system.

As a simple example (simple here is really relative), a linear system with flexible parts typically has complex poles with low damping: a controller inverting this kind of model is extremely sensible to the poles frequency and a small error may lead to the observed behavior (stable, but with large oscillating inputs) or worse (straight instability). This is one of the issues you have when you want to point a satellite (with large flexible solar panels) in the right direction.

Don't know how much all this is relevant to what we see in GPB, but the very fast handlebar shaking we see looks very suspect to me too.

MaX.