Originally Posted by
srode1
The only thing I can figure is maybe Continental calls them 40mm because they flatten out more at the contact point making them perform like a 40mm tire, although I haven't seen anything that supports that.
Sometimes they under size tires save weight making them seem lighter than comparable tires (that might actually be 42mm). It also allows them to be compatible with more frames. Doesn't bother me, as long as I know it before buying them!