Brian: I'm sure you have standard 700 / 28" sewups. Smaller sizes are almost always marked, ie: 26". I've never seen 27" sewups. The problem is that the bike industry is bereft with holdover and misnomers of over 100 years. The French were the true metric and the lost the int'l dimension war. Somehow 28" became the standard in the 1890's era and clinchers and sewups were same sizing ,and the 700 was the metric equivalent. The 28" dimension has held on even till today and many sew up tire companies use that number to this day. Our 700c clincher and the sew up rim diameter are basically the same, about 5mm smaller than the 27" rim but the 28" sewup is 700 in size and smaller than the 27. Many of the 28" tires are measured outside diameter, the rims are 700 so that often a 28" tire will fit a 700 rim, or visa-versa. Now that this is perfectly clear you'll have no problem telling your sizes apart.You just have to know what the hell you are doing. That's where many years of experience has helped, or even better for newer people to our fun game, hobby, sport, many afficionados will refer to Sutherlands Guide. Remember that sewups come slightly looser and tighter from the companies, and the looser fit saves the pressure on your eyeballs when you are stretching it over the rim. Clinchers are the same, some are finger busters, and others are a breeze. Confidentially I suspect it's an English plot to bring back Whitworth sizing and the memory of Dunlop and restore Brittania and rule the waves again. Its the Victoria's Secret of Cycling. Ted Ernst Palos Verdes Estates, CA
> I've got two NOS tubulars that have no size printed on them, they are
> CONCORDE CRITERIUM, Made In Singapore. They fit onto my 700C rims OK but
> they go on with not much effort, I'm used to really struggling with new
> tubs
> to get them on the rims, so now I'm wondering if I have a pair of 27 inch
> tubs, how can I tell?
>
> Brian Booth
> Toronto, Ontario, CANADA
>
> .......__o
> .......\<,
> ....( )/ ( )