I went out at 5 psi on rains at GoPro for Stars. The track was almost completely dry and I was gambling that the rain would come in the middle of our second heat on Saturday. It paid off, and I was the fastest kart on rain tires in the dry, but it ended up absolutely downpouring. The low pressures meant I was 5 seconds off on a fully wet track, but still 7 seconds faster than any of the drivers on slick tires.
I use mag wheels because that’s all we could find when we first needed to get rain wheels, and they’ve worked perfectly fine for me. The biggest things in rain racing is tire pressures and knowing how to adapt to the rain.