Here's a few thoughts about improving the tire strategy system, since I've complained about it at BRC76.
Let's take the race at Betonschleife (BRC76 Booklet) as an example:
If you want to run on a 1 stop strategy there you'd start on inters and after about half the race switch to drys.
The way to do this with the current parameters is the following:
Choose a point in race progress a bit after half the race, when the rain should have gone, for your planned stop. This depends on how far you estimate your car to go on 1 tank of fuel, let's assume 60% of the race.
Set the margin for unplanned stops to count as planned relatively wide. If your car can do 60% on 1 fuel tank, you'd set it to 20% (so that if you pit on 40% it counts as the 60% stop).
Set a value for at which track humidity you want to change from inters to drys. Ideally, this value should be hit just before your planned pitstop, but it has to occur within the margin you set. If it occurs before 40% you take an additional stop. If it doesn't occur before 60% you take an additional stop afterwards.
Set the value for when to change from drys to inters relatively high, but it has to be below the track humidity at the start. If you set this value too high, it could happen that you just start on drys and after a few laps pit to change to inters.** If you set it too low and after you've switched to drys a rain spike occurs, you'll switch to inters and then back to drys, which causes 2 unneccessary pitstops.
[ ** @Der_Bayer , I'd need you to confirm that if humidity is between the margins, the "dryer" tire is chosen. If I'm wrong here, point 4 is invalid for this specific problem. It would then be problematic if the rain forecast is the other way around. ]
Now to some possible solutions:
Option for a fixed strategy where you only change tires on planned stops to the type of tire you've specified before the race.
I've already discussed about this with Der_Bayer some weeks ago. He said it would be chaotic if there was unforeseen weather; which is a point that I can see. But then this is also the type of strategy that you have in mind when specifying values for tire changing; its just not a 100% fixed thing but a hope-it-goes-as-planned (with some variety for when the weather really freaks out. I hope there won't be a constant 60% rain over half the race when the forecast said completely dry though. Going through short spikes without pitting should be possible).
The percentage values we have now, but 2 different sets of them. One for which tires to put on when doing a [planned, or unplanned (fuel, damage)] pitstop anyways, and another one for when to do an unplanned stop because of a weather change.
This gives you the option to put on the optimal tires on a planned stop, but only do an unplanned when the weather really seriously freaks out. I'd like that solution because it's still easy to understand and not much effort to fill in the values, there is however another one that I would prefer because it's even more specific.
That is, having percentages for when to do unplanned stops AND have one set of percentages for every planned stop you do. With this system you could do a planned stop before the track will dry up and already put dry tires on, and in the same race do a pitstop right before it starts raining, on which you put inters on. For unplanned stops that are not caused by weather this would leave multiple options, the in my opinion best one would be to add one extra set of values for all of those stops.
This is fairly complex though. Some tutorial for new users wouldn't be a bad thing on this, also you could think about implementing an "easy mode" that is similar to what we have now or to my point 2.
I'm open for discussion on the above suggestions or for completely different ones. The above were just what came into my mind when I did the planning for myself. If there's a better, completely different planning option we can take that into the list.