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I have a Cube Travel Pro, which comes with a belt drive and a Shimano Nexus 8 hub, model SG-C6001-8D. The bicycle is a bit over a year old and used for city commuting in all kinds of weather. Has probably about 2000 km. The hub has mostly worked fine, but there was a period in the winter with very cold temperatures (around -20ºC) where it was difficult to change gears, and in periods with rain followed by freezing temperatures it would refuse to change to the lowest gears (after 4th gear). I assume that was due to the ingress of water and some parts freezing internally. Finally, this summer it started again getting difficult to change to the lowest gears after some days with rain. After finally getting hold of the maintenance oil, I followed the dealer's manual and to oil it. I was shocked when I opened the hub.

Hub 1

Hub 2

Looks like the upper part of the hub (non-drive side) was shattered and there were bits of plastic and bearings all over. Some of the cylindrical bearings had fallen inside the mechanism, and I was surprised the hub was still mostly rideable in this condition.

My question is if there is any hope of fixing this type of damage, or is getting a new hub the only realistic option here? I am not familiar with the internals of these hubs, and this does not look exactly the same as I've seen in videos and other images. The damage seems to be mostly a plastic cage for the cylindrical bearings, but I have no idea if replacement parts can be sourced.

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    A Shimano hub should not be damaged with normal use within such a short period of time. Contact your dealer or Shimano directly.
    – Willeke
    Commented Jun 24 at 10:17
  • Update: contacted the dealer, who said that as soon as I opened up the hub, I voided the warranty. So it seems that to perform the oil maintenance that Shimano requires, one needs to take it to a shop! My LBS will not touch it (say they have too many bad experiences with Nexus 8 hubs). A good cautionary tale to stay away from Shimano Nexus 8 hubs.
    – tiago
    Commented Jul 3 at 9:12
  • Do not accept their statement. The hub is clearly faulty and within a reasonable period. If in top of that you need to open it for maintenance their claim is (nasty word here)!!!!
    – Willeke
    Commented Jul 3 at 10:21

1 Answer 1

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If possible you should take it to a shop and pursue warranty. The x-factor there is Shimano's recommendation to do the first oil service at 1000km.

The exploded diagram and spare parts chart is at https://si.shimano.com/en/ev/SG-C6001-8D-4131. As far as what to do about it mechanically, one choice here is how deeply you're going to inspect all the sub-assemblies. When something like this happens, metal bits can get anywhere and things can be running out of alignment, so all sorts of damage can happen. I would probably start here by cleaning the shell thoroughly and inspecting all of its races and the drive interface (the part where the core drives the shell) for damage. If you find the shell itself is not worthy of re-use, you're replacing the hub/wheel, no need to do surgery on everything else. If it's good I'd replace part 1 in that diagram, the Y3EK98010 - Internal assembly (axle length 187 mm), plus anything else that shows wear or damage. But, you ultimately want the hub to have a good long service life, and so if there's any wear or damage to any of the non-replaceable shell parts, just replacing the hub or wheel becomes the appropriate choice.

There's an in-the-weeds question here of who would be able to warranty it and with what, and how to navigate the situation best in value and timeframe terms. Any shop can attempt to warranty it with Shimano, but if Shimano agrees to cover it, they'll only have a hub or parts to send. They're not super likely (IME) to cover the real cost of a rebuild, and a dealer is going to be essentially doing you a favor by acting on your behalf at all as it's a DTC bike. Some brands who do IGH bikes (particularly long-running models) keep complete warranty wheels; it's possible Cube may have one if you try to warranty it with them and they say yes. Where you are in the world is also part of this; here in the US I know them as basically a DTC brand like a lot of others, but I understand their model may be different elsewhere.

Side note: Using the Shimano oil is all well and good, but if the cost or availability is prohibitive, using a motorsports gear oil and taking your chances is a way better plan than deferring maintenance completely.

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  • Thank you for the good suggestions! Essentially, replacing part 1 in the diagram is most of the hub anyway, even though I suspect the shell is intact. I'll pursue the warranty claim. Cube just says to contact the shop where it was purchased. Mostly, it was really nice to get confirmation that this type of damage is not normal, which was my original suspicion. The bicycle was not in any accident and has been well cared for.
    – tiago
    Commented Jun 25 at 11:18

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