Bottom brackets

there are over ten standards, differing in width and mounting method, i.e. whether they are threaded or press-fit. You can find the designation in the frame documentation or measure it on the old bracket. Creaking from the bottom bracket is usually the first sign that the bearings have worn out; don't put it off, because the play will also damage the cranks. Adapters allow you to combine some mismatched pairs, but not all of them.