I get a loud 'thrumming' noise from the tires between 40 & 50 - loudest first thing in the morning. It seems to go away after about 15 - 20 miles. I've replaced the tires; balanced them twice; had 2 alignments; replaced all four struts; and replaced the tie rods and the connecting bar. There is no perceptable shake or vibration while this noise is going on. I have also cleaned the inside of the wheels and the rotors, around the bolt holes, to make sure there is a good smooth fit.
Anyone got some ideas? This is driving me crazy!

Eric

Possibly wheel bearing/hub assembly. Notice any play in the front wheels?

Don't notice any play at all. I just had the struts and tie rods replaced a couple of weeks ago. The mechanic would have noticed then wouldn't he? If he missed it wouldn't it have shown up when the alignment was done? Should I maybe be looking for a new mechanic?