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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

elevendollar
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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 01 '21 at 12:36
  • Thank you for letting me know the name of the system. I will look into the paste. – elevendollar Oct 01 '21 at 12:45
  • Ungreased threads, e.g. in the pedals, can sometimes click, so greasing those might help. Maybe the eccentric bottom bracket shell needs greasing too... – Erlkoenig Oct 01 '21 at 14:24
  • @Erlkoenig Yeah, but that wouldn't explain why the clicking sound goes away when I adjust the bottom bracket. – elevendollar Oct 02 '21 at 09:17
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    Sometimes adjusting one thing unexpectedly affects something completely different It was just a shot in the dark, anyhow. – Erlkoenig Oct 03 '21 at 10:03
  • @Erlkoenig Good point. Appreciate it. – elevendollar Oct 03 '21 at 17:10
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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 03 '21 at 17:59
  • @Michael Thank you. I will take that into account as well. – elevendollar Oct 04 '21 at 06:29
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    It's not quite a dupe, but I wrote an answer to a similar question that might be helpful: https://bicycles.stackexchange.com/questions/12707/creaking-bottom-bracket/12754#12754 – jimchristie Oct 04 '21 at 12:48
  • Based on the sound and the timing, a loose pedal seems to be the likely culprit to me. To @Erlkoenig's point: It could be that the pedal and the bottom bracket are both loose and the extra play in the bottom bracket is compounding the pedal play to the point where it clicks. Good luck! Clicks, creaks, ticks, and related noises are super annoying! – jimchristie Oct 04 '21 at 12:54
  • Are you sure your bottom bracket is not broken, mine broke once (with a belt drive) and it made a cracking sound – Bart Oct 04 '21 at 19:33
  • @jimchristie Thank you. Super annoying indeed. As your answer suggests I will try to systematically check all the components. – elevendollar Oct 05 '21 at 06:08
  • @Bart How could I tell if my bottom bracket is broken? – elevendollar Oct 05 '21 at 06:09
  • @elevendollar I could feel it when I manually turned the crank without a load attached (maybe even when the wheel was in). You could feel it did not turn smooth, I think the belt drive puts some extra strain on the bottom bracket – Bart Oct 05 '21 at 09:06
  • @Bart Thanks, I will check that. – elevendollar Oct 05 '21 at 10:41
  • Extremely annoying. Is the bottom bracket made of steel (if you have a magnet, try to attach it to the shiny part). I suspect not, but I am wondering if it has to do with differential expansion/contraction and slight misalignments. Funny note: the manufacturer says "it consigns rattling gears, oily chains and regular maintenance to the past" yeah, now you have clicking belts and eccentric bottom bracket, welcome to the future :D ! ps: nice bike – EarlGrey Oct 06 '21 at 08:18
  • @EarlGrey Thank you, I will check that as well when I get home. Yeah, belt drive and hub gear is great when it works but can be a pain when it's not. Especially because all parts are expensive and not as easy to take apart. – elevendollar Oct 06 '21 at 10:09

1 Answers1

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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.

Stephan Matthiesen
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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. – elevendollar Oct 06 '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." – elevendollar 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). – Stephan Matthiesen Nov 13 '21 at 11:02
  • That is good to hear. Cube also never responded to my email. Great customer service… – elevendollar Nov 13 '21 at 15:08