Last week has been rainy around here and I got caught out a few times in real downpours. I expect the first bit of wet braking to be slow (squeezing that water layer off the rims), but recently my rear brake has been REALLY bad in the wet while front worked as expected for the conditions. After the rains passed & things dried out, rear brake worked fine again. Pads are DA, not worn out, and seem clean. Never had this happen before, and don't want it happening again. Only thing that I changed recently is that I switched chain lubes. Could the new lube have been splashing off onto the rear rim causing that poor rear braking issue? Other causes to check on?