i checked for missing balance weights inside and out during my initial visual inspection. the weights were fine. and this is not a "my cousin vinny" situation either. however, i did swap the front left and right tires, and the problem swapped sides as well. Arthur Dalton suggested that it's a broken tire belt, and it looks like he nailed it. i'm relieved to find out it's an easy fix, i just feel a little silly for not trying the swap in the first place.

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1994 E420
1971 Camaro