I just picked up a bottom bracket off of eBay, but i can't tell if the bearings are worn or not. It is from an 8 sp group set and is in nice condition, but it doesn't seem to rotate as well when turning the spindle by hand as the cage bearing BB I removed. It is not installed. I have no experience with sealed bearings and need some help. When can you tell when the bearings need replacing? At low speeds when turning by hand is it suppossed to feel stiffer than a loose bearing BB?