Dylan got these Bridgestone 10x4.5x5 YNP Rain Tires for his birthday last week. We've never ran rain tires before and he sure is excited to race in the rain. We still need to a get a rain suit (so if you have any suggestions on that I would be happy to hear them) but we also needed to find some advice on air pressure for these tires. The CRG Kart Chasis Set-Up Manual has been a big help in this. It recommends 25-30 PSI in extreme wet conditions, 20-25 PSI in moderate wet conditions and 15-20 PSI in drying conditions. We will also be switching back to slicks as soon as it is dry enough and will likely try to keep a proportional difference in PSI from front to back as we run with the same set-up under dry conditions.
It also recommends increasing the front track, decreasing the front track, increasing the center of gravity and increasing caster and camber if possible. I'm assuming the kid kart races will be a disaster in wet conditions so we will not be making any major changes unless it is going to be raining the whole race day. Let us know in the comments if you have any advice for racing in the rain!