Not very understand the bicycle, but that bearing is called hub bearing in the car, for this bearing to know a little.Considering that it's all about supporting the wheels, there's an analogy.Hub bearings bear radial and axial forces at the same time.Therefore, deep groove ball bearings cannot be used for this bearing.The best solution, or the common solution now is to use double row angular contact ball bearings (cars), double row tapered roller bearings (trucks, trains).
It can be seen that for this kind of load is more complex and the axial and radial bending moment force is full, this kind of double-row ball (tapered) bearing is generally used.The load of the bicycle is relatively small, so naturally will not choose the heavy cone bearing, so the double row angular contact ball bearing is the first choice, that is, the kind of "bead" used on the general bicycle, its inner ring and outer ring are integrated with other parts together, it does not look like a normal bearing.So the question "why not use ordinary ball bearings", in the other answers are explained from the cost and use, then as a bearing practitioner, can change the question to why not use ordinary deep groove ball bearings and use double row angular contact ball bearings?For two reasons:
- Double row angular contact ball bearing as a result of the existence of contact Angle, the axial and bending bearing capacity significantly greater than assigned by the double row deep groove ball bearing is clearly if there is a push to the left of the thrust ball, the ball can get better support contact stress (small), and the steel ball on the left side of the force will be amplified by like a wedge contact stress will also be greater.
- NSK Deep groove ball bearings have great limitations on the number of steel balls loaded due to geometric assembly reasons, and angular contact ball bearings can even be full of balls, and then the inner ring can be covered up.