Hi, I will get this bike for my son (https://www.cube.eu/en/kid/kid-260/te...-260-teamline/) . It features this bottom bracket (https://cycle.shimano-eu.com/media/te...9830667768.PDF). Its cranks are too long and I would like to swap them for a 130-140 mm ones. Any solution? Should I change the bottom bracket?
Cannot solve this easily.
Regards.

You can get something like these, or you can contact this guy.

If you switch to a nice square-taper BB, you can then find lots of cranks in shorter sizes. eBay has tons of them. That's what I did for my kids road bike.

+1 .. square taper, then you can even get a longer crank arm
re-machined with new threaded holes , put in the arms further in.