Examples are provided that describe a cycloid transmission with an adjustable ring. An example cycloid transmission includes a disc and a motor shaft attached to the disc. The motor shaft is capable of rotating the disc around an outer ring of rollers. The outer ring of rollers surrounds the disc. As the disc is rotated, contact is made between the disc and the outer ring of rollers. A cycloid transmission also comprises an adjustable ring that is interposed between the motor shaft and the disc. A circumference of the adjustable ring can be adjusted in order to cause expansion of a radius of the disc. This expansion will result in increased contact of the disc with the outer ring of rollers and thereby lower backlash during rotation of the disc.