GP Bikes beta18c available!
Started by Manu, June 17, 2020, 12:51:53 PM
Quote from: Myst1cPrun3 link=msg=106032After some testing, I believe I have come up with a theory and a possible solution to the seemingly random front end crashes, as well as the issues with camber changes mid corner.(Thinking MG hairpin at Victoria)I did touch on this in a previous topic before it was moved, as it got way off the original conversation point. (As much my fault as any that was so I apologize)Now:Until I started fiddling with tyres, I thought the front end crashes on camber changes was because of the suspension, and a lacking part in the simulation or mod..However, in the tyre files, max lean can be set using the DX1 and DY1 values.Now this differs per front and rear tyre so you can have a tyre have a larger max lean angle than the other.The bike will only lean to the angle of whichever tyre has the smallest max angle.So for instance if you let the front have a higher max lean angle than the rear, it is the rear that'll determine the total bike lean.This becomes important in camber changes.It's no secret the front tyre is narrower than the rear, so in terms of lean angle, it has a slightly different steering rate it seems. (Not sure on Reasons or physics behind this just how it seems)If you are on the max lean angle of a tyre, and then the camber changes, the bike does not get stood up, the lean angle changes to beyond the maximum set value in the tyre file, and a crash occurs with seemingly no warning. Typically these crashes are front end crashes as that's the narrower tyre and it's also what it's the camber change first.As a result I found giving the front tyre 0.1 extra lean on the DX1 and DY1 values when compared to the rear tyre helped a lot.This extra angle doesn't affect the bikes handling on the flat, as the rear tyre will be the limiting factor, but when the camber changes, it means the front doesn't simply 'fall off the edge' like is known to happen in GP Bikes.This isn't to say you can't crash, you can, it just adds a bit of control of the bike over camber changes.Here is an example of the M2v2 at the MG hairpin, where I was being quite aggressive on approach, and could make the apex confidently, despite the known issues.It is a marked improvement, but I am going to do more tuning when the 'big tyre update' drops for the v2
Quote from: Hawk on June 17, 2020, 12:58:51 PM@Mystic: I think Manu is trying to tell you that when tuning the tyres, you can't just alter a couple of values without those alterations affecting other factors in the tyre file that will need adjusting too to compensate? Correct me if I'm wrong Manu.
Quote from: h106frp on June 17, 2020, 01:22:30 PMDont want to become overly involved in this but its worth loading MaxTyre to visualise whats happening. A tyre has no such thing as a max lean angle, its just the point where the slip becomes greater than the friction holding the tyre against the tarmac (until you roll of the edge) and is mainly down to how well the contact patch deforms around the profile and circumference (no idea if this is modelled), curiously you have maximum contact patch when leaned at around 45-50 degrees with modern designs.DD is correct, a narrow tyre of given torus will arc around a turn faster (smaller radius) than the wide tyre as it rolls around its profile faster for a given lean, narrow tyres need less lean than wider ones for a given turning arc, hence the front washing out first and the perceived nimble handling of small bikes - you only run a tyre thats just wide enough for the power and weight of the bike - oversize tyre are a silly styling thing and ruin handling. Unfortunately narrow tyres do not appear to model well at the moment and the performance appears to drop on a cliff edge below a certain width.
Quote from: HornetMaX on June 18, 2020, 02:42:26 PMAs h106frp tried to explain, there's no such a thing as "max lean angle" in GPB. Even on a real bike, it depends on plenty of factors: MotGP bikes can maybe lean 60deg, but in some cases you can lose the fron when leaning 45deg or even less ...In GPB, on top of these, you also have the virtual rider in the loop, so drawing conclusions is very hard.As h106frp suggested, I'd advise to have a look at how GPB tyre model works, what DX1 and DY1 are and what their effect is (in a nutshell, they define the max longitudinal and lateral "grip" a tyre has at optimal longitudianl slip / sideslip angle).Long story short, increasing them you've just given your tyre more "grip" so yeah, it handles better. No big surprise.There's little chance that anything good can be obtained reasoning on things like "front and rear tyre have different max lean angles".P.S.If I recall correctly, PiBoSo long ago stated he's aware of the issue of front losses on turns with camber: if the true solution was simply to give the tyre a bit of extra grip, that would probably be already done. It must be way more complex than that.
Quote from: h106frp on June 18, 2020, 10:16:08 PMI have been going through the usual re-tuning of a bike using Victoria and I have developed a bit of a new theory on what occurs at the bottom of Lukey Height/MG. After noticing the problem only ever occurs when entering the turn with high lean (you can always blast through it any old how when you pick it up after a drop) I wondered about chassis flex and damping, theory being that as the bike has a high lean angle we lose damping and travel from the suspension units and become dependant on the mechanical flex and damping - much in line witrh Vinis comments about the bikes being overly 'stiff' but maybe with a slightly different perspective.With the newer inertia calcs it appears we have a bit more range to play with in the damping and chassis stiffness ranges and it does improve the situation very noticeably if you can add a bit of flex and damping to the chassis. It might be worth you trying and comparing it to what you obtain from tyre adjustments.
Quote from: HornetMaX on June 19, 2020, 11:56:49 AMSide note: I think Victoria is a good test track. It has a bit of everything. Not sure why Vini crusades against it