I too had the bearing failure on a previous Zero.
I learned the following from examining wheels used by Zero-
First, the quality of the hub and repeatability on the machining of the bearing receivers was poor.
Second, the bearings used are not designed for axial loading. These are standard roller ball bearings and can take only a small percentage of their load rating along the axle line. Cars have tapered bearings (along with the steering neck on bikes) so you can tighten down on the them; they accept radial and axial loads. Zeros standard ball type bearing can not tolerate axial loads.
Third, the width of the aluminum sleeve that runs on the axle between the two inner bearing races (the spacer between the inner bearing races) was shorter than the measured distance the hub establishes between the outer bearing races. Even using a press to make sure the bearings were completely seated in the hub, I still could not get the spacing remotely close to that needed by the inner bearing race spacer. ANY amount of axle nut tightening made for a huge axial pre-load on the rear bearings and caused the rear wheel to slow much faster when I spun it on a bike stand (with the belt off). I did not have a new spacer to see if the above poster's theory about crushing the spacer is accurate. I just did as they did and made one from steel.
The bearings should have a taper element to them or at least be of the deep race variant of standard ball bearing where there is increased axial load capability. In addition, there needs to be accurate spacing of the inner and outer races so as not to pre-load the bearings in the axial direction when you tighten down the axle nut. Lastly, I did not test the theory but I suspected that, as the hub heated from rear disk thermal loads, it would expand more and more quickly then the steel inner race spacer which could put significant axial load stress on the bearings. The hub heating would be spreading the outer races more and faster than the inner race spacer could keep up with. I got rid of the bike.
Bike one 0 one.....
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Topic: 2014 DS Bearing Problems + Pics (Read 1720 times)