i ordered a new sram gxp bottom bracket to replace my old one that was getting noisy. it's the kind with the external bearings with the plastic tube that runs between them. anyway, i removed the old one and installed the new one no problem. while putting the cranks back on, the spindle wouldn't fit all the way into the drive side bearing. looking at the bearing there's a dust cover that fits the face of the bearing but also fits inside the hole that the spindle fits in making it to small for the spindle. the cover comes right off so i removed it and installed the cranks. is the dust cover necessary? did i completely screw it up?