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EDIT: Dropped it off at my local bike shop and the mechanic had the following to say about it:

Bottom bracket very low quality, also worn bearings. Due to open frame type was a lot of dirt inside that could make noise. Excentric bottom socket was removed, cleaned and greased. New bottom bracket installed. Tightening bolts on frame were also corroded. Those were replaced and greased.

Original Post below:

I did read some of the other questions regarding clicking sounds when pedalling. However my bike is a bit different to the bikes from the other questions so I hope this question is fine.

My bicycle:

Cube Travel EXC 2021 with 8-speed Alfine hub gear and Gates' belt drive

The problem:

It started making a clicking noise (see video below) when I pedal hard (uphill) ever since I moved to a more hilly location. I've only had the bicycle for 9 months but because I am not in the same country anymore as when I bought it I can't make use of warranty.

It has a round bit (what is the name for that kind of system?) for adjusting the tension of the belt by turning it. It's held in place by two bolts that come with the instruction to only tension it up to 8Nm. I use a torque wrench to make sure I don't tighten it too much and make sure to tighten it evenly (is there a best practise?). I have attached pictures below.

Every time I loosen the bolts, adjust the round bit and therefore the tension of the belt (make sure it has the correct tension) the clicking noise goes away for a few days and then comes back.

Therefore it must have something to do with that round bit but I am not familiar with that system so I hit a dead end.

Video and pictures:

The clicking noise video can be found here (youtube video).

The system for adjusting the belt tension: enter image description here

The two bolts + instructions enter image description here

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    It’s an eccentric bottom bracket. Maybe carbon installation compound (it’s a paste to increase friction) would help.
    – Michael
    Oct 1 '21 at 12:36
  • Thank you for letting me know the name of the system. I will look into the paste. Oct 1 '21 at 12:45
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    Sometimes adjusting one thing unexpectedly affects something completely different 😉 It was just a shot in the dark, anyhow.
    – Erlkoenig
    Oct 3 '21 at 10:03
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    I wouldn’t rule out the rear hub either since it’s affected by the belt tension. I would try to take out the silver eccentric part, clean all surfaces and install with carbon installation compound. For the two screws you could use threadlocker. When tightening, alternate between both until they are truly at 8Nm. If that doesn’t help I’d start suspecting the rear hub or the bottom bracket bearings.
    – Michael
    Oct 3 '21 at 17:59
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    It's not quite a dupe, but I wrote an answer to a similar question that might be helpful: bicycles.stackexchange.com/questions/12707/…
    – jimchristie
    Oct 4 '21 at 12:48
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+100

Hard to diagnose from a distance, but I had exactly the same symptoms and similar setup (a belt drive with an excentric bottom bracket).

I couldn't really find a problem but the sound went away when I put grease on the bottom bracket, so I left it at that. Then a few months later the axle in the bottom bracket very suddenly became totally loose, within a few kilometres from fine to 2-3mm play, and the noise was back.

Bike shop looked at it and found that the bearings inside the bottom bracket were held by a plastic bit that just disintegrated, so I had to get a new bottom bracket. It was probably cracked much earlier, creating the clicking sound at every turn, but then had settled into a non-clicking position before failing totally.

The bike shop also said that they know that in my bike model the bottom bracket is a bit cheaper than it should be, good enough for most people, but too weak for a heavy rider in a hilly city. So they put in a much more solid bottom bracket. So I think it is worth asking a bike shop that sells your model of bike about their experiences.

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    Thank you very much for your answer. I have been suspecting that it might have something to do with the hillier landscape I live in now. That would support the theory. I have also contacted Cube about my issue but so far no reply. Will also contact the webshop where I bought the bike. Oct 6 '21 at 17:18
  • You were spot on! I brought it into a bike shop and this is what they had to say "Bottom bracket very low quality, also worn bearings. Due to open frame type was a lot of dirt inside that could make noise. Excentric bottom socket was removed, cleaned and greased. New bottom bracket installed. Tightening bolts on frame were also corroded. Those were replaced and greased." Nov 12 '21 at 15:44
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    @elevendollar Interesting that it's exactly the same! I'm glad they found the problem, hopefully it'll be ok now. Mine works perfectly now (it's been a year since it was replaced). Nov 13 '21 at 11:02
  • That is good to hear. Cube also never responded to my email. Great customer service… Nov 13 '21 at 15:08

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