Tire curves are certainly just part of thing, sure they are base and other parameters and variables are then used to shape it to get final grip.
There is tire load, pressure, temp, and at least with rfactor there is quite many parameters to play with to get grip to what it should be in all situations so it is not easy like drawing proper curve, not at all like that, there is other parameters that are need to be adjusted so that behaviour of tire is more real like.
For example tire load effects to lateral and longitudal curve is one thing. It is not going to be anything real even curve would be spot on if these parameters are not set well and their effect is HUGE, badly set values do cause feeling like that car has predefined spin angle (99.999% of mods?
) even most perfect tire curves has been used.
So to funny part, how we can discuss about these parameters of LFS if we have no way knowing how those are weighted and what they are using, we can say tire curves are ok, but is parameters, does temp and load modify curve just linearily or are they possible modifying peak?
One picture I saw from this thread did show how when tire load is increased, even tire had rather flat curve without peak on low loads at high loads there was more peak, even more load and even more peak there was even overall grip level was higher. So it can't be modified linearily if we look realistic behaviour.
Now what I see in ISI curves, those look like high load ones, but they should not be as there is parameters to take care of falloff and peak things so I would say that is where they have gone wrong. But also you should keep in mind when looking ISI curves is that they are often 0-100 degrees of slip angle while typical curves we see are 0-20 maybe even 0-40 and it might do some difference to curve too if you plot only first 20 degrees, but surely there is too much peak.
I'm still learning lot of this, but that is now what I have understood, might be wrong might be right, you tell me