I've got a 98 s70 T5 with almost 150,000 miles on it. A couple hundred miles after I had the tires balanced at an NTB, a periodic "whoomp..whoomp..whoomp" sound started coming from the passenger front tire area. It sounds like something is rubbing and the sound does happen more often the faster the tire is spinning. It was originally intermittent but it is now louder and constantly present. The sound is also louder if the steering wheel is biased a little to the left or right. The brakes work normally, the car handles fine and I haven't detected a drop in mpg.

I had a mechanic look for the problem when I first noticed the sound, but he didn't find anything. I did notice the passenger front tire had two unusually large balancing weights. I took the car back to be checked at a different NTB and they confirmed the tire was improperly balanced. Rebalancing the tire did not eliminate the sound. I asked them to look for the source of the sound but they didn't find anything.

Has anyone else had a similar experience and found a cure, or have some suggestions on what to check next? Thanks.