Wobbly tires... balance issue? wtf??

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i noticed a slight wobble in my rear tire (kind of a bulge at one point) when i switched from 2.3" trail tires to 48c cross tires on my 29. i couldn't figure out what was causing it so i switched back and everything was fine. now, after replacing the tubes it's happening in front and back!
i've taken good care of the wheels, they are perfectly true, and i checked the rim tape too. everything seems to be in order.
is it the tubes, could the bead be bent, is this a defect in the tire or rim (all are WTB), or... ????


bouncing down the road is getting annoying, any help would be greatly appreciated.