Tire grip seems a bit exaggerated while the physics model might need a review

[MaverickFlanker 0]

Hello,

I'm an aerospace and physics engineer and I'm very passionate about car racing in general as well as aviation. The reason I'm here is not to criticize nor to point out irrelevant elements but to rather help to take a bit deeper look into primarily important details that regard a realistic simulation in it's full word. I've just got the DIRT RALLY sim, as others talked about how realistic it is, only with the hope that at least now a truly realistic physics model would show up upon rally gaming (yes, games not simulators), but while playing it didn't take long to notice 2 very major issues regarding the simulation.

1. If let's say you try some burnouts (the most simple fun stuff anyone tries in their first tests) with a rear wheels drive car, you have a constant angular velocity (some constant degrees per second of rotation) as your rear wheels keep spinning at quite a fast rate (which helps keeping the car do nice swirls around a point), the car may sometimes slide slightly backwards during the burnout, which is normal and always may happen in reality, but, for some unknown reason yet, the rear of the car instantly stops like it glues to the ground instead of continuing to spin. Every time the car manages to go past 90 degrees of  sliding angle during a burnout or in any circumstance where there is a quite low sliding speed (let's say 10..20km/h) and the slide angle becomes greater than 90 degrees the car stops dead for a split moment (the angular momentum suddenly becomes zero instead of conserving further) then continues to accelerate forward like it started from a standstill. Where does the car's inertia suddenly disappear there? Is there some problem with the physics model code? I don't know if I made myself completely understood about this strange car's reaction, but if one may try to replicate it will immediately spot the same thing and understand.

2. I've played for quite a while and by just visually comparing a car in the game with the same car in reality in similar turns at similar driving speeds, it turned out that the tire grip in the sim might be a bit higher than real (giving similar conditions of course), which breaks the authenticity of the experience and simulation level. We all know that simulating the tire grip has many variables. One of the biggest variable is the general grip or static friction coefficient between two surfaces (for example, tire and asphalt). The dynamics friction coef. may rather be determined using real life tests. Other very important variables are: tire pressure (which affects tire contact area and behavior under loads), tire temperature, tire compound and profile as well as some small other variables. I don't have access to the files to read the values which correspond to tire traction/grip calculation, yet if I would, I would definitely play with those values a bit..., not to "slide" away from the real values, but rather to get them closer.


Best wishes and regards!