So I bought this Kent brand bike from Walmart for $50 on clearance a few years ago and I want to upgrade the bottom bracket and one piece crankset to a hollow spindle ceramic bearing bracket but I'm not sure exactly what parts I need. Should I buy a bottom bracket and crankset that fits directly into this American style bottom bracket? Or should I buy one of the American to Euro conversion kits and smaller bottom bracket? Also I can't seem to find exactly what these American to Euro conversion kits turn your bracket into, is it BB30? I'm so confused! The brackets are 63mm wide, but I'm not sure how big the opening is since I haven't removed the old one yet, but it's 57mm or 2 1/4 inches diameter on the outside. Also how do you know what length spindle to buy?