Squrilly rear end in rain - new tires, bad wheel bearing

Are those tires Sumatomo? In either case my 2 cents.

When I was a lad, I had a tricked out Fiat X19, I was totally taken with the mid engine superiority design. So much so that I didn't respect the properties of wet pavement and took an unexpected spin on an off ramp; thank god no other cars were around. As it turned out, I was glad to learn my lesson in a car. Years later during my motorcycle phase, I learned that rain raises, oil droplets and other road deposits in the street. In short, pushing any vehicle with any tires in these conditions is a bad idea. Having said that, tire pressures, compounds used and tread design all contribute to performance. Making a great dry tire sacrifices wet performance and vise versa. Check out the tire rack website sometime, it has some great information regarding these principles. Of course if the geometry of the suspension is off everything I said means nothing. IMHO, a wheel bearing wouldn't cause this type of erratic behavior.

PS if you really want to experience your car, upgrade the rubber. My dealer thought he was doing me a big favor putting two new sumatumos on the car when I bought it. I ditched those tires a month later with a ton of tread on em and was glad I did.