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The issue

My 2019 cube stereo 150 rides very wobbly, to the point where it's outright dangerous on speeds above 40km/h. I pinpointed the issue to the lower bolt that connects the springed rear part of my bike (blue arrow): Arrow indicating the location of the bold on a schematic

As you can see in this picture, there is a lot slack. the white plastic you see in there is a piece of zip tie, I can fit another one of those at the left bottom side. Image indicating the amount of slack

This is how this looks without the triangle thingy. enter image description here

Without the piece of zip tie, the rounded triangle can move up, down, left & right, but also rotate a lot:

Image indicating the possible movement

Gif indicating the possible movement

I thought there might be a missing cap that should be locking that bolt in place, but seeing this video, it seems that he has the exact same protruding end of the bolt (albeit way cleaner):

Screenshot of a video displaying the bolt on a brand new cube 150 stereo

Tried solutions:

  • Repair shop: I tried both a big repair shop and a local repair guy. Both didn't seem to have even found this issue. Only after I took matters into my own hands I noticed this.

  • Replace the components: I sourced & bought an entire kit with the same product ids (which you can see in the picture) and while it definitely was an improvement, there is still a dangerous amount of slack. This was the kit I bought (I bought 2, one as a spare). I don't think I had to use the blue tube though. That may indicate that I missed a step. enter image description here

  • McGyver it: I added bits of zip-tie pieces, filled the gaps with glue and added some duct-tape on top of it to keep it in place. This actually worked not too bad, but the zip-tie plastic wears of rather fast. I think I should redo this procedure about monthly to be safe.

I would love to hear any better solution than the temporary zip-tie fix, preferably keeping my bike fully suspensioned. I was thinking something like strong sealant.

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    Where you the original owner and was this a problem you've had since purchase but taken some time to identify the source? Not 100% what the linkage should look like, but is it torqued correctly? Have you contacted Cube directly, because going by your photos and description seems like a design flaw that they may have an aftermarket fix for
    – Hursey
    Apr 24, 2023 at 5:13
  • @Hursey I am the original owner and I think the problem arrived after 2 years of riding. I torqued it correctly indeed (in fact, it was how I found out the issue with the triangle moving around). I didn't find any other questions from people with this problem (however it might linger around on the internet in German somewhere) Apr 24, 2023 at 5:45
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    What parts did you replace? Since that's the main pivot I'd expect it has bearings and or bushings. When was the last time those were replaced? I'm guessing that the rounded triangle piece is not what's supposed to hold the chainsyay/swingarm steady and something else is the actual cause.
    – shox
    Apr 24, 2023 at 6:16
  • @shox, I did replace the main pivot set with the official set (updated the question). I checked the product id on the bolt with what was used to be in there. Apr 24, 2023 at 8:19
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    How did you discover this problem? Did it start recently, after a notable incident, anything?
    – MaplePanda
    Apr 28, 2023 at 1:44

3 Answers 3

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+50

As pointed out in the comments, that you could replace the bearings by hand when installing the kit isn't a good sign, but it could offer some clues what to do next.

If they're a slip fit, install them with retaining compound. If the bores for them are wallowed out completely, that could be the whole problem and is likely not repairable.

It seems possible that your existing "blue tube," which is likely installed into the front triangle, is damaged or worn and could be the origin of the problem. When you go back in to secure the bearings properly with retaining compound, extract the tube and replace it.

To be clear, the contents of the kit make it look like the intention is for the blue tubular spacer to be between the bearings in the front triangle, and then each bearing should get one of the black round spacers on top of it to go between swingarm. Tightening down the pivot axle should then draw out any slack.

Some frames have snaprings that act as the back stop for bearings. If yours was like this and they were missing or damaged, that could cause looseness in this area.

The "chip" element in question on this bike fits very loosely, which suggests that the design isn't trying to rely on a precise fit between it and its bore to prevent looseness in the rear end. Designs that do work like that usually have a tapered or conical fit to the chip, so that it gets drawn in securely when you tighten it down. If this problem developed over time and wasn't an issue when it was new, it seems unlikely that the chip is the cause. If it is the cause, then that would indicate you need to bulk it up somehow. There are metal reinforced repair puddy products that might work well here. You could fill the bore with the putty, find some kind manufacturer-prescribed release agent and coat the chip with it, smoosh the chip into place, then take it out after making a perfect indentation of it and let it cure.

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  • I appreciate each and every answer, but this seems to be the most likely culprit & solution. Thanks! May 3, 2023 at 4:42
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Unfortunately Cube doesn't supply exploded suspension diagrams online or repair/maintenance manuals like some other manufacturers. Maybe those are exclusively for dealers?

In any case I was able to find the following image on a message board:

Cube Stereo pivot

The dirty rusty bit (which I suspect is a bushing) is what should be holding the axle steady in the swingarm/chain-stay. The circular triagular bolt is that shape so you can tighten the axle without needing a wrench or something to hold it in place. It isn't a perfect tight fit because its job isn't to hold the axle in the correct place (i.e. keep it from moving side to side), i's job is to provide tension.

I don't know what the piece is on the other side of the swingarm, but presumably it's pressed into the swingarm. In your case it is likely:

  • missing
  • rusted or deteriorated to the point where it is no longer tight
  • ovalized or worn

It could also be that it is tight around the axle, but something has happened to where it presses in to hold it steady. In any case it would be best to remove the chain-stay to view it from the inside.

It is also suspicious that so much thread is showing on the pivot bolt. I couldn't find any images of a new one in place, so this may just be the design, but generally I'd expect there not to be any threads showing as it's a risk they'll get damaged and you won't be able to extract the bolt. It could also be I'm mistaken and that's just grease. If it is threads, then it seems your axle is threading in too far, which could be due to a missing washer/spacer etc.

It may be a simple case of replacing the part marked in red, however if it isn't holding due to damage where it presses in you'd need new chain-stays. If it's a non-replaceable part, you'll need new chain-stays. Different manufacturers have different retention times on parts. If all frames that use this design are out of warranty it could be Cube won't have any replacement parts, in which case your only option would be to make your fix more permanent with the understanding that's not how it was designed to be supported and may result in the chain-stay cracking around that bolt.

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    I don't deal with suspension, but I suspect that is indeed one of the suspension bushings. If they take it in to a different store or call Cube, the OP could say something like "there is play in my suspension bushing or pivot" (then describe which bushing)
    – Weiwen Ng
    Apr 24, 2023 at 18:47
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    Agreed. I'm surprised any shop would shrug their shoulders so quickly, but maybe prompting them with your suggested comment would have helped. I'd definitely want it at a shop that deals primarily with MTBs. I'm sure they've seen similar many times on various brands. A Rocky Mountain dealer should be very familiar with these types of issues if a Cube dealer isn't around.
    – shox
    Apr 24, 2023 at 18:53
  • Interesting take, I'm going to check the replacement parts I got to see if I missed out on something, I might have been too focused on the triangular part serving as the "bearing" mechanism. Apr 25, 2023 at 11:30
  • I had two bike shops: one big shop that has dissappointed me many times: fixing things that ain't broke and not fixing things that are actually broke. The small shop I went to started out super promising, but when I came with this issue to him he took my bike hostage for around a year (blaming it on covid). Apr 25, 2023 at 11:32
  • A year? That's crazy. I have not yet had a bad experience at a bike shop, but the local shops are really good.
    – shox
    Apr 25, 2023 at 14:52
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I think you're missing some kind of spacer, washer, or bushing between the threaded ice cream cone-looking piece and the frame bearing. I'm not very familiar with Cube, but there are some tell-tale observations to make here.

Notice that in the animated GIF, the chainstays are wobbling up and down as you manipulate the fastener. This shows that there is extra space somewhere in the assembly that shouldn't be there. Perhaps the blue piece is a bushing which is supposed to go around the axle inside the frame and take up this gap?

Secondly, in the picture without the ice cream cone, there's nothing between the bearing and where the ice cream cone would be. From an engineering perspective, this doesn't make too much sense. It would be worthwhile contacting Cube or a dealer of theirs to try to get an exploded view diagram or other documentation. Alternatively, a dealer could disassemble a factory bike to see how that's assembled as a comparison.

I found a picture of a similar looking Cube setup from this link.

enter image description here

Similarly to what Shox noted, there's far less exposed thread here than what you have on your setup. More evidence that something might be missing. Do note that the ice cream cone here seems to fit into the chainstay's socket quite a bit better than how it does on your bike, although it doesn't appear to be an absolutely perfect fit either--there looks to be a gap on the bottom. I'm therefore pretty confused as to how this arrangement is supposed to work even in a factory-fresh setting. There doesn't seem to be any firm connection between the bearing and the frame.

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