It's the usual behaviour of a car, yes, but it's not the usual PC1 behaviour. The main problems with PC1 physics, IMO, were grip gain/loss (felt too digital), and the differential. Grip under braking is what I understand you were talking about in your post (correct me if I'm wrong).
yea, digital is a good word, the gradient was off.
I didn't want to talk physics with you, but here we go... my problem is not really "grip" under braking, but turn-in response. A good racing driver steps on the brake (hard! in a car with downforce), then leaves off the brake the slower the car gets (as the grip gets lower from less downforce), before he is off the brake entirely, he starts to turn-in. I'm not really talking about trail-braking to get the most deceleration out of the time before the apex, I'm talking about weight-shifting and most of all combined-slip. Under braking front tire load is higher(weightshift) so you got more grip on the steered tires, also, when turning in under braking the outer front tire has a higher load than the inner tire and has more grip, can take the brake force better then the inner tire.
Now the real thing: The inside tire... if you brake too much, it easily locks up (less grip than outside tire), if you brake too little, it has
less grip, because the more slip, the more grip, unless you go over the limit... just from lateral cornering force, the inside tire does not get to the limit. Additionally, this inside-tire brake-grip helps the car to rotate.
In pCARS1 some cars had tremendous understeer under braking. This should only be the case if a tire locks up and has almost no grip anymore. Even worse, as soon as you'd leave off the brake, all of a sudden the car (with the weight still shifted to the front) would go for the still steered angle from your wheel input and you'd get heavy oversteer.
Differential was my main complaint, though. On corner exit, some classes more than others, would lock down the direction under too much throttle, and would keep locked even after release. Gr. 5 class comes to mind. GT3 was okaish, I guess. It felt like racing on wet conditions more often than not and was not only unrealistic, but also unfun.
If I understand you right, you're talking about on-throttle understeer because the rear wheels refuse to turn and different speeds as if they are 100% locked by the differential.
And... I don't really remember that from pCARS1. Some cars have on-throttle undertseer. A Gr.5 Porsche 935 has a wider rear track than in the front, also wider rear tires, that alone can cause understeer, but it also has no differential, but a spool (basically a 100% locked differential). I don't know for sure, but I assume a BMW 320 or the Capri also had pretty heavily locked diffs that should cause off-throttle, but also some on-throttle understeer in tighter corners.
For GT3 cars on-throttle understeer can be caused from the mid-engine layout if the weight-balance is slightly towards the rear.
