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Can someone tell me exactly what is happening here?

Started by GDUBMX, March 31, 2017, 11:09:41 AM

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GDUBMX

https://www.youtube.com/v/vFuZN91MINc

as you can see, you come out of a corner and maybe counter steer slightly after the rear steps out a bit and then you go into this crazed front end speed skating thing?  :o
<br />GDUBMX YouTube<br />

teeds

As soon as I see my bike doing this I lean forward and it stops. I guess the bikes weight under power is towards the back and makes the front end light, with little front traction the rider then goes to extremes to try and keep the bike at the lean angle you're asking for.
"Damn dirt bikers!" - Bubba

Jose Reina

March 31, 2017, 01:09:35 PM #2 Last Edit: March 31, 2017, 01:12:48 PM by Jose Reina
That's a shimmy, I guess you know what it is.
That happened to me in real life with the supermoto, in a straight at 120km / h and I had a big accident hahaha.
Unfortunately, in the Gbbikes and Mxbikes, these shimmys are very common, and they exist since the first Alpha of GPBikes.
This basically happens when the front wheel is not 100% in contact with the asphalt (before doing a wheelie for example), which is what happens to you in the video, when you accelerate, the front wheel wants to get up and while You are turning the steering, then when the front wheel is in contact with the asphalt at 100%, its wheel is turned, and that is when the side movements or shimmies begin.

It is very difficult for me to give you a correct explanation, so it is possible that another person is able to explain it better, but basically, I think you can understand something I have explained.

Also I would like to leave the opinion that this problem comes as I said from the first version of GPbikes (Alpha), and I personally think this happens because of the way the bikes have to turn. If you look, when you do a wheelie on a straight, and you want to turn from left to right, you can not, and you will only see that what moves is the handlebar, but the bike is still straight doing the wheelie. This happens because the way of turning the bike is 100% on the steer, which I see incorrect, because in real life, any rider is able to spin the bike without hands on the handlebars, or do a wheelie and spin the bike by doing a wheelie.

This is why I said, that the physics that makes the bike turn, is on the steer 100%, that's why the direction is so sensitive and makes those movements strange (that the shimmies exist and are normal, but here many times Is excessive)

I hope someone has been able to understand something that I have explained hahahahaha, sorry but you know that I am very very bad with English, and helped me google translator hahaha.
That's why I'm really sorry if you can not understand me ;)

Ruubs

Good theory Jose, but I'm certain this isn't shimmy. I've had shimmy way to often in real life.

This is just because when we accelerate we wheelie a little bit. As I've previously stated somewhere on the forums is that the handlebars twist WAY too sensitive in the air. When we have our wheel one centimeter above the dirt we'll already have the sensitive handlebars. We then try to get the handlebars straight again so we steer the other way, but since it's so sensitive the handlebars are facing the other direction. It's very hard to keep the handlebars straight when this happends. That's what causes the 'shimmy' in MXB. So this isn't the same shimmy as in real life.

GDUBMX

Right OK so in otherwords..

https://www.youtube.com/v/rTEnnyqA71k
<br />GDUBMX YouTube<br />

Asdrael

I never have that, I'm betting you have a very low Direct Steer value.

As far as I understand Direct Steer, high values mean your stick is actually your handlebar turning force, low value your bike leaning force (roughly don't burn me), which is a result of the handlebars turning.

So if you have very low DS values and the front wheel is offering no resistance (aka - off the ground or sliding) your handlebar is going to turn like mad trying to provide a leaning force that it can't, as it has nothing to apply it to.

If you have high DS, your handlebar is going to turn following your stick (unless you are actually dribbling) so you won't see that happening.

I don't really see a solution to that, maybe putting DS to 100 when your wheels are off the ground automatically? Might feel weird for the transitions though.
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Jose Reina

What Asdrael says is also right, with Direct Lean to 100, these shimmys do not happen or happen less.

I particularly use the Direct Lean to 20 or as high as 40 (For me much more real), but then if it is true that I can happen more times this shimmy.

Here an example of Shimmy or Wobble

http://www.youtube.com/v/54fTFm5Dc-I&featurereload

Ruubs

I've used direct steering on 100 forever and have this problem quite often. So that wont fix it.

Shimmy isn't this Jose. That's different and I've never had that in this game.

GDUBMX

Ah ok I thought Asdrael was talking about direct lean, yeah mine is a 18 and I personally hate the feel of anything close to 100. So can we determine whether this is a bug/physics related or this is supposed to happen. It happens quite often on a lesser scale, to be fair it's actually really flipping annoying
<br />GDUBMX YouTube<br />

Jose Reina

March 31, 2017, 04:04:13 PM #9 Last Edit: March 31, 2017, 04:08:19 PM by Jose Reina
Well, I do not know exactly if it's technically that or something else, but basically it's similar, strong steering movements from side to side.
The difference is that on asphalt is more abrupt because there is more grip. In dirt it is softer because the front wheel slides more, it has less grip, so the shimmy or wobble is not as abrupt.

I have had this shimmy or wobble, especially in GpBikes, the more speed is easier it happens, but here in MXbikes also happens.

Luckily I have already become accustomed to this and I consider it normal and I adapt and I manage to control it, but if it is true that it seems excessive in comparison with reality.

Ruubs

Believe me, shimmy irl on dirt is as abrupt as it could get. Dirt isn't flat at all, when you land a little sideways with ur handlebars you'll crash, no doubt, or get very lucky.

Irl dirt shimmy the front wheel doesn't slide at all, plus you go over braking bumps etc. I've done a lot of no handers already! Luckily never crasher cuz I could somehow save it.

Never buy a crf250 06..

Jose Reina

I believe, I do not question what you say, I just say that for me is similar to what happens in the video of GDUBMX a shimmy or wobble or whatever you want to call. I simplify things a lot.

In my KTM sxf 250 of 09, it was very abrupt of direction and also happened those shimmys, you have to be very very strong to be able to support them

HornetMaX

Quote from: Asdrael on March 31, 2017, 03:34:07 PM
As far as I understand Direct Steer, high values mean your stick is actually your handlebar turning force, low value your bike leaning force (roughly don't burn me), which is a result of the handlebars turning.
As far as I've understood (from GPB) Direct Lean 100% means your stick is the target lean angle. With Direct Lean 0% (long time ago, Direct Lean was only On/Off, no intermediate value) there's some sort of "magic" filtering applied to your stick position  so that the control becomes less sensitive (Piboso himself used to say that Direct Lean ON/100% is supposed to be used with high precision devices like joysticks or better, not really joypads).

From what I see, it seems to me that starting with bike vertical and wanting to lean fully left, Direct Lean 0 or 100 behaves in a similar manner. The big difference seems to be when you want to pick your bike up (e.g. go from leaning left to vertical, or clearly from leaning left to leaning right): with Direct Lean 0%, if you just put your stick in the middle, the bike will react slowly, it will come back vertical veeeeery slowly. So slowly than in fact you're obliged to "overshoot", i.e. you will push your stick not to center but to the right, to make the bike pick up faster. Once the bike is vertical, you will move your stick to the middle. With Direct lean 100%, you don't need that. On the contrary, as the stick output is the target lean, you have to move it more carefully.

Short version: with Direct Lean 0% you can bash your stick left/right like a madman (actually, you almost must). With Direct Lean 100% you have to gently move the stick as if conducting brain surgery on a beloved one.

After years of debates in GPB (mind, MXB is pretty different) my conclusion is that one is not better than the other, in GPB you can be fast with any of the two. But it takes time to get accustomed to one coming from the other, so that's why people using it at 100% say 0% is shit (and vice versa, of course).

Personally, I tend to use very high values of direct lean in both GPB and MXB (by high I mean 100% :) ).

P.S.
I have a joypad ans I've put some "stick extensions" on it (something like this: https://www.kontrolfreek.com/thumbsticks/fps-freek-classic.html). I think they make you more precise.

CSchmied986

No matter what you have your settings at, this is just one of the MANY physics bugs that are hopefully being worked on.

CSchmied986

Yes, there are ways to help reduce it, but even Pib says there are major physics issues, which is all im saying.