Originally Posted by
SkyDog75
According to the ETRTO (European Tyre and Rim Technical Organization), a 20 mm rim will ideally be paired with tires whose width is between 28 and 44 mm wide.
I looked on ETRTO's web site and couldn't find this info. Schwalbe publishes a chart that it claims comes from ETRTO but they must have made a mistake.