changing my tube one day I noticed that after re installing the rim on the bike the tire dipped into the rim on the front and back of the bike. they are joyteck rims like the ones on my specialized and I have removed those tires plenty of times and they are fine. Being that this is the first time expiriencing this problem does anybody know what to do about this? I checked the rims and they are not bent at all aswell as re applied the tires twice!