i just bought two old road bikes (schwinns) mainly for just riding around town. when i got them both desperately needed tires and tubes after i replaced them and took the bikes for a spinn all was fine, other than a constant bump bump bump bump when i ride. at first i thought the rim was bent or had a flat spot but after flipping the bike to its saddle and spinning the tires all seems fine. i've also tried swapping the tires around for both bikes but it seems unlikely that i bought two bikes with 4 bent rims. i've also read that the cause of this could be the tire not seated properly on the rim but i don't know how to fix that? i've watched many videos and i seem to be doing it correctly. any suggestions??? please help me out guys i don't want a bumpy ride.