To add to all the oddities that have people are identifying/researching, here's another one I think I've figured out now.
There's also something a bit odd-feeling with steering when the stick is near-centred, but I can't quite put my finger on what it is yet (it's only a minor thing anyway).
So it seems that the game adjusts steering
saturation depending on your speed. Saturation is the %age input on your controller that translates to 100% steering in the game. It is like a deadzone setting, reducing the available input range of your controller stick, but at the far ends of its input, rather than at its centre.
At lower speeds, PD appears to have set saturation to be less than 100% controller input. You can see this if you stop your car, and slowly start moving your controller stick. You'll see the steering wheel in-game stop moving before you've moved your stick all the way to the right/left. This has the effect of making small steering inputs at low speeds more sensitive than they really should be. I don't know why PD have done this.
Additionally, I think this is combining with the game's overly low steering
linearity in a bad way. Low linearity means that, normally, the steering is insensitive to small inputs (eg. moving the stick from 0-50% only moves in-game steering from 0-25%), but conversely, steering is sensitive to larger inputs (so moving the stick from 50-100% moves in-game steering from 25-100%).
Because of the saturation thing I'm not entirely sure that the game has overly low linearity, but I suspect it does because when I was driving the Gr.3 Jag round BB Raceway, on the banked sections, where you're at high speed and having to maintain a large, steady steering input, the car felt quite twitchy and difficult to manage.
If I'm correct about these saturation and linearity settings, then PD have managed to create a setting that is both sensitive at low speeds with small steering inputs,
and high speeds with large inputs. This is very counter-intuitive - with other games I'm used to one or the other, but not both! I think it's this that's giving me the 'odd' feeling mentioned above, and combined with the game's slow steering speed, it's really making it more difficult to anticipate what the car is doing than it should be.
I mean these things aren't game-breaking or unplayable or anything, but I am in the bizarre situation where I now have better controller settings for PCARS2 (which actually has options to adjust all this stuff) than a for GT game..............no offence to SMS, but if you'd said that to me a month ago, I would have laughed at you!