hey, i have a bmx, it currently has unsealed 3 peice cranks, with looseball bearings. i took it apart yesterday and put new bearings in, and to day it was loose so i made it tight again, so i went out for a ride for a couple hours within the first 15 minutes the nut was loose(holding the other washer and the nut holding the bearing in place. the nut was rubbing right up against the crank arm. why does it keep coming loose, and when i took it apart today, the bearings completely fell apart. so tomorow im going to the store to get new bearings (2$ each), so please to me how to keep the spindle from coming loose and to install the bearings properly.