Originally Posted by
icemilkcoffee
I specifically said 26" tubulars, which are 650c diameter. This is a well established nomenclature. Just as a 28" or 27" tubular refers to 700c ISO 622 , not 27" ISO630. The OP asked about 26" tubulars, and those would be ISO571 650c diameter. Now maybe the OP meant to ask a different question, but I am just answering the simple question he posted.
Again, tubular tires, exist for 26" Mountain bikes in ISO 559.