I have recently replaced the stock steelies on my MY98 outback sport with OEM 02 WRX rims/RE92's that have 1500 mi. Please correct me if this was a mistake, but I assumed that since the new rims/tires (had them shipped 1000 mi.) were still mounted and weighted, I would not have to balance them myself. Anyway, after approximately 500 miles of driving with them, I noticed a slight rythmic grinding noise from the right rear which increased with speed. After making another 300 mi. trip, the sound had gotten much worse. The performance of the car is not noticably affected, but I am afraid of possibly causing more damage as the sound is becoming more and more obtrusive. My questions:

Should I avoid driving the car before getting it fixed to prevent damage?

I've read lots about the defective rear wheel bearing in similiar models, and also about a transaxle grease recall, Am I on the right track, or could it be something else?
note: rear drum w/ ABS

Could the new wheels/tires be in any way causing or contributing to the problem?
Your replies will be much appreciated...

P.S. Hey, I bought a non-dealer used car w/ >100,000 miles and had no problems for over 6 months!- Not too bad, I think.

 

also no irregular tire wear (so far)