I’ve got a Shimano GRX Di2 dual shifter/lever that I want to install on a new Carbon handlebar (Carbonda CGB01) . The problem is that it fits until it reaches the curvature and then it gets stuck. I tried losing the bolt all the way and it still won’t move. I am not sure if my clamp is defective or there is a way of dealing with this. enter image description here

  • I can't read the Chinese on the technical drawing, but it appears to show a 24mm +-0.1mm outer diameter for the drops, which is very close to the maximum 24.2mm inner diameter of the clamp per Shimano. It's not clear from the handlebar diagram at what point it starts flaring to the 31mm diameter of the tops, but you could simply have reached the point at which the flare starts, and have reached the maximum 24.2mm size of the clamp.
    – DavidW
    Commented Oct 27, 2021 at 16:41
  • This video and others use the same handlebars without any issues though.
    – Daniele
    Commented Oct 27, 2021 at 22:00

2 Answers 2


If it's obstinate about going any further than pictured, you could tighten the lever on now with normal torque and then loosen it back and see if the band clamp takes a new set at all, which might help get it the rest of the way. When they're brand new they don't really have their final resting shape.

  • tried to leave it overnight and use soapy water as well. Unfortunately it didn’t work. What I discovered is that if I remove the bolt and try to insert the clamp on its own, it enters really easily, with the bolt on, it doesn’t.
    – Daniele
    Commented Oct 30, 2021 at 2:36

Flip the fitting 180 degrees, so the mounting bolt points into the middle of the curve. That will allow a little more room. Then push it around to the final resting place and lastly spin it on the bars.

You might need to add a little lube too, dish soap and water would be fine. Try hard to avoid scratching the bars.

  • 1
    Tried turning it around in any kind of way. It seems that when the bolt faces inwards there is even less space. I tried even with soapy water to no avail.
    – Daniele
    Commented Oct 30, 2021 at 2:37
  • @Daniele okay great work. I suspect your next option is filing the inside of the slot on the clamp (don't file your handlebars!) to make the slot slightly longer. Also, you could remove the bolt and thin the head to gain a little space too. Take off as little metal as possible.
    – Criggie
    Commented Oct 30, 2021 at 7:50

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