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[Kocho]

I can see in the third photo it says Koyo 6904RS

http://www.dbearings.com/KOYO/KOYO6904RS

[Ser15]

Here are more details

Enviado desde mi 6045B mediante Tapatalk

[MostlyBonkers]

Thanks Ser15.  No word from Zero or the dealer yet. I'll chase them tomorrow.

[BrianTRice@gmail.com]

Okay so just that brand against the documented bearing specs? Now to source these...

[Ser15]

In addition to the bearings you must buy the rubber seals of bearings, send photo reference. I do not have a part number, In my case one was not destroyed and used to buy new ones.

[BrianTRice@gmail.com]

Okay so they're still not sealed bearings so you need the rubber seals, but they manage to last longer?

FWIW when my 13DS bearings were replaced, I got a fresh set of seals just hoping that new ones would prolong life. Unfortunately I only have spare OEM bearings around and not the seals.

[Ser15]

I put it together like factory, with rubber seals.
New bearings are sealed.
Attached rudimentary scheme I hope you understand, I'm sorry for the basics but I do not have any other. I used the original aluminum parts in my case were intact and not damaged.
Attached photos of how it is today. In the photos you can see the aluminum part and the rubber seal

Enviado desde mi 6045B mediante Tapatalk

[MostlyBonkers]

That's great Ser, thanks again.  Also thanks to Brian for updating the wiki.

Zero are shipping a new wheel over. Don't know the ETA yet. It's a 2014 wheel and it's likely to have bearings already installed.  Hopefully they'll last at least 8,000 miles like the first ones did.  After that I'll use these great tips to hopefully make the next fix last a lot longer!

[odedmaz]

Is the new wheel covered by warrenty?
Glad it's working out for you.

Sent from my XT1585 using Tapatalk

[MostlyBonkers]

I've been told by my dealer that it won't be covered by warranty as bearings are a consumable item. However, they've submitted a technical report to Zero and hope that there will be some goodwill.

[lolachampcar]

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.....

[BrianTRice@gmail.com]

This is great information all around, thanks to all! I'll have a queue of things to write up once my move is settled more.

[MostlyBonkers]

I'm still waiting for the wheel to get to the dealership. Thanks lolachamp for a brilliant post and everyone else that has contributed. It will mean I can keep riding in future, rather than worrying that the bearings will go any minute.  Somebody made a schoolboy error on the drawing board by the sound of it.

Thanks also to Brian for all your efforts with the wiki - this will certainly help many others.