I've had my 00 Insight with 30,000 for only 3 months. I recently have noticed a low done or hum from the rear at around 45 mgh. It seems to occur in both 4th or 5th. It appears to go away once I go above 48-50mph.I've recently upped my tires to 42 psi. Has anybody else noticed a similiar low rumble or is it that I'm just to new to all the sounds of the car?