My Chiron 3D printer, like Ender 3 and CR-10 had a less than ideal belt-path. I guess it is not a big deal but I could not stand it.
I managed to get a working printer again, but I was not suspecting I would need to disassemble all X axis to mount these new pieces. And I needed a new belt too, as the original one was too short. And a good collection of zip ties too. And a lot of patience, and a file.
So you have been warned, it will take more than one hour to install this and it may take away some of your sanity for good.
Right now my printer is printing again (with a too stiff X-carriage but it seems to be ok). I will check later if X-axis scale needs to be adjusted due to this fix.
Ah, yes, what these parts are for is for the bottom of the belt to be a straight line instead of the V-shape of the original design. You always want the parts of the belt attached to a moving carriage to be parallel to the axis of motion. Creality and Anycubic opted for an easy to mount but geometrically incorrect path.
I guess another way of adressing this problem is to keep the belt-supports of the carriage and modify the two ends (motor and idler).
You can see a poorly lit video of it in action: https://youtu.be/Bc3glm2kDgw
And an estimate of how the belt length changes as the carriage moves along X axis:
Such a change in length will translate into a non-uniform tension along the path. On top of that, the belt can rub the sides of the extrusion channel while moving which will degrade it sooner too.