And where is the noise coming from??Did you check your rear hub?If you tightend your whole bottom bracket and made sure there is no contact with your crank arms,changed the pedals,changed bearings and cages then it can only be coming from your rear hub.But if its not that I think your out of luck!No way this should be happening to all four bikes.Did you put your bottom bracket bearings in correct?Ball bearings to the inside and cage tops out?If there was ever a problem like that it could crack one or both of your cups.It will also chip the inside of your cups and your bearings will hit these pits and cracks and it will make noise as your arms turn.