Rain

I would love to know what tyres I should use for different types of rain, just to know what tyres for what mm of rain, so what's high rainfall and what's low, cuz I wanna know what to use tonight thanks.

You will find the following in the rules-
2.3 Tyres - There are four compounds of tyre available in iGP Manager, they are: Soft, Hard, Wet (Intermediate) and Wet (Full). There are no restrictions on how you use the tyres. Each compound is best suited to a different set of circumstances outlined below.
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[*]Soft - A dry weather compound. Great for qualifying, the soft tyre is designed for raw speed and can be very effective in low ambient temperatures due to its tendency to heat up very quickly. Though on high wear circuits or in high ambient temperatures they may suffer from overheating and high wear.
[*]Hard - A dry weather compound. Not the best qualifying tyre, and doesn't have the ultimate speed of the soft tyre. However, it makes up for this deficit in durability, making it ideal for long stints. In some circumstances it can be competitive with the soft tyre on pace, for example high wear circuits or very high ambient temperatures. Such conditions hurt the soft tyres, but help the hard tyre get to optimal temperatures.
[*]Wet (Intermediate) - A wet weather compound. Designed for low to medium rainfall. It does not work well in high rainfall or dry conditions.
[*]Wet (Full) - A wet weather compound. Designed for medium to high rainfall. It does not work well in low rainfall or dry conditions.
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Jake cleared it up very nicely. It's always good to take risks though, if you're not sure and the rain changes during the race. I think it's a lot to do with common sense though, because it's reasonably simple to work out what you'd use with what types of rainfall.