A dial indicator at the flange will tell you if the flange is bent. Im not so sure you will be able to check for bent axle with out removal and a long enough machined straight edge and feeler gauges. Tire hop= possible bad tires:broken belts. Or suspension components:shocks,bad spring. Drum could be bad. My guess is bent flange and get the drums measured and turned. I think if the axle was bent you would have bearing noise also or soon enough. Just my guess.
