Shaft bowl and axle shaft
For many years, the adjustable central shaft has been the most common type of central shaft. It can be applied to all bicycles, including race bicycles. This kind of central shaft has low cost, but the consumption and assembly process are relatively time-consuming. Moreover, its biggest weakness is that there is no good sealing system. The grease in the central shaft will quickly emulsify and be polluted, so as to speed up the wear of the whole system. The new generation of sealed bearings has dealt with this problem and is a very cost-effective promotion project.
If the central shaft is in good condition, it can be used again after it is smooth. However, it needs conditioning after installation. Install the adjustable shaft bowl and feel a little resistance. At this time, the axis should have no clearance. If you must continue to tighten the adjustable shaft bowl to eliminate the gap, you should change the whole central shaft system. If there is no problem, install the locking ring, which can be adjusted when fixed, the shaft bowl does not move, and tighten the locking ring. Check whether the axis can rotate smoothly, and then reinstall the crank. The conditioning process may need to be repeated several times.
Seal center shaft
Before the appearance of the external central shaft, the sealed central shaft continues to occupy the middle and high end. This universal square hole system has guided the market for many years and is still used in many middle and low-end bicycles.
In addition to identifying the specifications of splines, pay attention to the length, width and thread specifications of the central shaft. These contents will be marked on the shaft body.
Outer bearing center shaft
The main defect of the adjustable central shaft and the sealed central shaft is that the maximum diameter of the axis that can be installed in the five-way joint is limited. The external bearing system makes the bearing located outside the five-way, so a thicker hollow axis can be installed in the five-way. This structure not only reduces the weight of the central shaft, but also increases the hardness. The harder and lighter system allows the cyclist's strength to be transmitted more directly to the transmission system.
With the progress of technology, most manufacturers have further enhanced the hardness of the central shaft and integrated the shaft axis with the drive side crank to make the weight lighter. However, some manufacturers still use independent axes.