I have a 2002 Volvo S40 that when I accelerate a thumping or knocking sound accelerates with it. The tires are new but it's only audible at speeds around 40mpg or above. Consistent sound dat...dat...dat...dat etc. It's only when I drive forward. I went into a parking lot and did the full turn around thing both left and right and no clicking or knocking sound. Go straight 40 plus miles an hour dat...dat...dat...dat...

 

When did this sound happen? After the new tires? I've seen new tires that were bad out of the shop because they were seconds.

It may come down to removing each tire and going over it and the brakes, rotors, etc.

Is there any play in the steering wheel when it happens?