Bottom bracket: The bearing system the pedals (and cranks) rotate all over. Contains a spindle to which the crankset is connected along with the bearings on their own. There is a bearing area within the spindle, and on each with the cups that thread to the frame. Dropout: a bicycle https://bike-engine-details95837.alltdesign.com/how-much-you-need-to-expect-you-ll-pay-for-a-good-parts-bike-mtb-54090479