French size crossed my mind, too, of course. But the diff in circumference between the 28mm French and 28.6mm English tube size is under 2mm, which seems too little to explain it. I haven't tried the too-small part on a French frame yet, but I doubt it will be a good fit there either. And why don't the catalogs mention that they're available in different sizes?
David Bean
Arlington, MA USA
beandk at are-see-enn dot com