Solved

Tires after rain

Thanks for whoever knows

It depends on a few things so there is no x laps is right for all occasions (for instance how deep the water is when the rain stops). 

Having said that, the game has changed recently and tracks are now very slow to dry out.

Recent example, 50 laps in Brazil to go from 5mm to 1mm.

The best approach would be to try and spectate a few wet races to give you some idea and if your race is going to be wet try and attend the race.

I set mine at 10 laps to 15 laps (depending on the track and approx. weather) when i cant watch the race. 3 is not enough at all.
50 seems a lot to me, but it might still occur since igp keeps tweaking the weather settings from time to time when people cry wolf.
If u are able to watch the live race, id set this number to "higher then the number of total laps in the entire race", so the autopit does not pull u in too early when the track is still wet. In which case u can decide for urself when to pit. Watching the race is usually better than hoping u hv the right numbers set in extra options...

"Timing is everything, n it seems to be the key"

I thought it was ridiculously long at the time, maybe I should have mentioned the race was 2x speed. If the drying is time based rather than lap based it may go some way to explaining why it took so many laps. 

Three nights ago MJL league racing in Monaco. Race start 21:00, 50% race length (39 laps) at 1 x speed.
It had been raining on and off for the entire day. I logged on at 20:30 and it had stopped raining and it remained that way until the race ended at about 22:00. So that's at least an hour and a half with no rain.
A minute before lock down I did a practice lap which indicated approx. 2.0mm water.
At 21:00 the cars lined up on the grid, water depth approx. 1.7mm.
The race ended one hour later after 39 laps and there was still 0.1mm water on the track, the inters tyres lapping at about the same speed as SS.
The winning strategy was 20 laps inters / 19 laps inters.
So, yes, a lot more than three laps!

I gotta admit. Today we raced china. 
It stop raining prior to setup. Everyone started on dry tires.
We started with 0.3mm and ended with 0.1
28 laps (50% x2(i think))