I have 4 Bridstone Potenza RE050 245/40 (standard on the sports package)-wide tires on the back.

Recommended tire pressure is 38 in front and 46 on the back.

My tires will loss pressure gradually and then stabilize around 32 in front and 35 in back (over a 4-6 week period). Indicator light does not come on..

Is this normal?

No it is not normal. Somehting has to be causing the air pressure loss. I am not sure why it would stabilize though. A 10psi drop in the rear would be significant and would cause a drop in fuel economy.

I assume I should bring it in to the dealer.

thank you

Unfortunately I don't. But loosing that much pressure is not normal.

its not normal unless you were measuring 38-46psi hot... then let it sit in a cold weather environment then yes... it could drop 6 psi....