If you bought the tires on the cheap..I'd be suspicious of them.Ive been thru this with the stock tires..always had a thumper that finally went away after tires where changed ( Tire people never admit fault).....been back to dealer many times or it and inally gave up and wore em out...wheels changed( for other reasons) and all that....tires..een new ones can be bad...take it to another place for advise.. but dont mention anything..see what they say outright,,then explain it.

 

A belt separation in one of the tires could possibly be at fault. Maybe try rotating the tires to see if the results change. I've had tires fool me into thinking I had a brake problem before. Harder thumping with harder braking. I think the rotors are probably junk too, at least from what I've heard and read on the forum. Good luck.