Originally Posted by
well biked
Off topic a little, but regarding the "700c" designation, the "c" was originally a width designation. A, B, C, and D designations were used, with A being narrowest, D being the widest. Sheldon explains in this paragraph:
French sizes:
In the French system, the first number is the nominal outside diameter in mm, followed by a letter code for the width: "A" is narrow, "D" is wide. The letter codes no longer correspond to the tire width, since narrow tires are often made for rim sizes that originally took wide tires; for example, 700 C was originally a wide size, but now is available in very narrow widths, with actual outside diameters as small as 660 mm.
To expand on this: 700 (and 650) told you the outside diameter of the inflated tire. As noted, A, B, C, D were progressively larger tires. A 700A tire was the same outside diameter as a 700D, but much smaller width-wise (and ergo, the rim would be larger than the 700D). The last vestige of this in our modern system is 650B/650C (B being used on smaller-wheel bikes for smaller riders, and sometimes found on Randonneur bikes, while C exists mostly on time-trial bicycles). It is not hard to see, then, why one would prefer the modern system of [BSD]-[Tire Width].