Patent ID: 7762571

Claim:
A bottom bracket assembly for a bicycle frame comprising: an upper portion integrally formed with the bicycle frame, said upper portion provided with a semi-circular interior surface receiving a crank shaft assembly, said crank shaft assembly comprising a crank shaft having a first circular bearing coupled to one end of said crank shaft and a second circular bearing coupled to an opposing end of said crank shaft, said semi-circular interior surface of said upper portion defining an upper bearing preload surface; a lower portion detachably connectable to said upper portion, said lower portion provided with a semi-circular interior surface receiving the crank shaft assembly such that when said lower portion is coupled to said upper portion the crank shaft assembly is secured therebetween, said semi-circular interior surface of said lower portion defining a lower bearing preload surface; said lower portion having at least two lower mounting elements positioned on opposing sides of said lower portion and said upper portion having at least two upper mounting elements complementary to the at least two lower mounting elements; at least two mounting devices positioned within said at least two lower and upper mounting elements, said at least two mounting devices passing through said at least two lower mounting elements into said at least two upper mounting elements to secure said lower portion to said upper portion such that said upper bearing preload surface and said lower bearing preload surface provide a controlled bearing preload surface interacting with said first circular bearing and said second circular bearing, said controlled bearing preload surface being obtained by simultaneously machining said semi-circular interior surface of said upper portion and said semi-circular interior surface of said lower portion while said upper portion and said lower portion are clamped together, resulting in a consistent bearing preload on said first circular bearing and said second circular bearing when said upper and lower portions are disassembled and reassembled; an alignment protrusion and a cavity for interacting with said alignment protrusion such that when said lower portion is fitted against said upper portion, said alignment protrusion engages with said cavity to align said at least two lower and upper mounting elements; said lower portion being completely detachable from said upper portion.