I have the following warning on my (carbon) CUBE stereo 150 race (2019) : DO NOT CLAMP warning

Ultra thinwall tubeset DO NOT CLAMP

Currently I clamp my bike like this, and make sure that there is nearly no force applied. The rubber on the clamp keeps it from sliding away:

enter image description here

Does thinwall tubeset means that the entire frame of my bike should not be clamped or only where my dropper post is? If so, how am I supposed to perform maintenance on it?

ps: there seems to be no manual for CUBE 2019 bikes.

  • 2
    Can you clamp onto the seatpost instead? Its a cheap(er) part to replace than the whole frame, if a clamping misadventure does occur.
    – Criggie
    Sep 6, 2019 at 13:49
  • 1
    I think thats doable, however it's a dropper post so it might be more dangerous to do so? Sep 6, 2019 at 13:51
  • 1
    There's nothing wrong with clamping a dropper post. Just be sure it and the clamp itself is clean
    – Paul H
    Sep 6, 2019 at 15:50
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    @Criggie is correct that an alternative workstand would be a good option. One should note that they're probably more expensive than the ones that clamp to frame tubes (one example of each in the links in my response). That said, this is obviously still cheaper than having to replace a carbon frame out of warranty. And let's face it, if it broke where it was clamped, a dealer inspecting the frame would know for sure what had happened, so you would definitely be out of warranty.
    – Weiwen Ng
    Sep 6, 2019 at 17:29
  • 1
    Problem is, I think it would take an ultrasound scan to detect any damage, and that is expensive and requires a specialist. You can tap the tubes lightly with a screwdriver handle and listen if the tone changes around the clamped area - Google the tap test for damaged carbon. However, I believe that test will not detect all damage. I think that at this point, just keep riding it, keep an eye on the area, maybe do the tap test occasionally. The main thing is that I would not clamp that area further.
    – Weiwen Ng
    Sep 7, 2019 at 2:07

1 Answer 1


I believe that you should not clamp anywhere on a carbon-tubed bicycle. As @whatsisname discussed in this Stack Exchange post, carbon fiber can be made very strong, but if you want it to resist clamping forces, you have to specifically design it to do so. That would add weight. All our fancy carbon frames are designed to be strong in some directions only, and they are not designed to withstand clamping forces. For that matter, the tubing on aluminum frames is very thin, and I believe the general recommendation is not to clamp aluminum frame tubes either. One best practice would be get a cheap alloy seatpost and clamp that. Some discussion here from a Trek dealer in Chicago. They point out that clamps really concentrate the clamping force in a few places on the tube. So, you could be exerting more clamping force on the frame than you perceive.

Park Tools has a pro mechanic stand that clamps bikes through the front axle. If you go to the page for their home mechanic stand, the picture clearly shows them clamping a bike by its seatpost. They also suggest that you can clamp a dropper post with some precautions. The link goes to a YouTube video, and their synopsis of the issue starts at 11:00. The link should play from that time, but you can replay that video from the start if you are interested in an engineering discussion of clamping forces on seatposts.

If you search the internet, I think you'll find some people who say they've clamped their carbon frames gently without issue. They may well be right! However, the issue is that they may have caused invisible damage inside the carbon. Raoul Luescher, who repairs carbon bikes for a living, discusses that issue in this YouTube video. His discussion is not specific to clamping, but he makes the point that you can cause delamination (fancy term for a fracture) in a carbon bike from something as simple as letting it fall over at a coffee stop. Importantly, you can have a delamination that's not visible from the outside of the tube. It's possible that the delamination will propagate (i.e. get worse) over time, and then fail unexpectedly. He specifically said in the video that he gets a number of failures while "just riding along". His point is that well-made carbon fiber won't fail like this; there has to be a flaw (e.g. manufacturing process left voids, which propagated over time) or invisible damage.

Please note: this does not mean you have killed your fancy carbon frame. It merely means that clamping your frame, even lightly, is not safe in the long run.

Side note: An extremely expensive but flexible adapter solution for your stand is Silca's Hirobel, further discussed here. This supports a frame from below the top tube using rubber wheels, and it places rubber straps around the top tube. This is probably not worth it for most people. I am including this link for fun. And who knows, you might decide it's worth it in terms of hassle saved.

  • 1
    Carbon really does seem like a sub-optimal material for a bike frame when you state it like that. Excellent answer!
    – Criggie
    Sep 7, 2019 at 0:21
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    @Criggie Thanks! You know, I did not mean to convey that carbon is a poor material for a bike frame. Remember, we make airplanes with a lot of carbon parts. You crash, you get injured. If an airplane crashes ... Luescher makes the point in other vids that carbon is an excellent bike frame material - but it is sensitive to how you handle it. He reminds us that metal frames can also fail. However, it's true that metal frames are probably less sensitive to handling issues, and when metal is near failure, the signs should tend to be noticeable.
    – Weiwen Ng
    Sep 7, 2019 at 2:01
  • 2
    Instead of the Silca's Hirobel, a fake top tube bar used for bike racks will work for 1/4 of the price.
    – mattnz
    Sep 7, 2019 at 2:56

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