700B was the same size as English 28 x 1 1/2in rims with a bead seat diameter of 635mm. 700A was the same size as 28 x 1 3/8in rims which were obsolete in Britain by 1920 with a bead seat diameter of 642mm. And there was the 700 rim equal to 28 x 1 1/4in with a BSD of 647mm which were obsolete in Britain by 1920 though I believe they were popular in Canada quite a bit later.
There use to be an equivalent range of continental and British tyre sizes for 26in (650), 24in (600), 22in (550), 20in (500) and 18in (450) rims all with rims ranging from no suffix and suffixes A to C.
700D was a actually a bastard size invented by GT in the late 1980s.
The tyre sizes with a decimal point are a completely different animal and do not have metric sized equivalents...
Hilary Stone, Bristol, British Isles
Jan Heine wrote:
> 700C tires have been popular in France at least from the 1920s onward.
> Of course, back then, every country had their own sizing. The British
> measured their wheels in inches.
>
> The French measured in millimeters, by the outer diameter of the wheel.
> There were several 700 (mm) sizes, each with a different-size rim:
>
> 700D was for the fattest tires, and used a small rim (587 mm)
> 700C was for fat tires, and it had a relatively small rim (622 mm)
> 700B was for narrower tires, so the rim was larger in diameter.
> 700A was for the skinniest tires, so the rim was even larger.
>
> Sorry, I don't know the measurements for 700B and 700A rims...
>
> For some reason, by the 1920s, 700C had become popular for all tires,
> and so today, we use narrow tires on 700C rims.
>
> Anyhow, those sizes date back to not very long after pneumatic tires
> were invented. The first pneumatics were custom-made, and often, you had
> even two different sizes on the same bike! Once tires became
> mass-produced, you had to standardize.
>
> You may think that it is cumbersome to have different rim sizes, just
> because the tire width was different. However, for the mass producers,
> it was great. You could use the same frame with narrow, medium and fat
> tires, just by changing wheels. The brakes clamped to the seatstays and
> fork blades, so they were easy to slide up or down. It kept production
> efficient! As a rider, you could conceivably keep two wheelsets, and
> ride the same bike with narrow or wide tires, depending on your mood...
>
> But all this is outside the CR timeline... By the 1930s, the most
> popular sizes in France were 700C and 650B, with a few 600s thrown in
> for good measure.
>
> In recent decades, the U.S. has seen British imports with 26" and 27"
> wheels, French and Italian bikes with 700C, 650B and 650C wheels, plus
> GT had the brilliant idea to remake (for a few years only) 700D wheels.
> The result is total confusion, especially when you realize that there
> are two 20" sizes (406 mm and 451 mm)...
>
> Fortunately, in recent years, the ETRTO standard has become accepted,
> and puts some order into this mess:
>
> 26" = 559 mm
> 650C = 571 mm
> 650B = 584 mm
> 700C = 622 mm
> 27" = 630 mm
>
> And then you have the silly mountain bike sizes of 29" (which really is
> 700C = 622 mm) and now 28.5" (650B = 584 mm). Once the ETRTO sizes are
> universally accepted, life will be a lot easier...
>
> On a different note, does anybody know when Italians adopted the French
> standard of 700C wheels? What about their city bikes - what wheel sizes
> did they use?
>
> Jan Heine
> Editor
> Bicycle Quarterly
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