Re: [CR]Requested Clarification: 700C &less-experienced

Example: History:Norris Lockley

Date: Wed, 26 May 2004 00:02:08 -0400
From: Joe Bender-Zanoni <>
Subject: Re: [CR]Requested Clarification: 700C &less-experienced
To: Sheldon Brown <>,,
References: <> <p061005f5bcd973ce1f1a@[]>

Buried underneath all this tire size info is the fact that the minor diameter of a sewup rim has been the same forever (okay-since 1895 or so). Fatter "single tube" tires are labeled 28" going way back. Narrow sewup rims and tires existed for racing way back too. Eventually most sewups were about 27" and then they got a little smaller- therefore 700C. My point is that as roads got generally better and tires got smaller the 2nd banana clinchers have had to keep up with the sewups that had the same basic rim configuration all along!

A recent 35mm Dugast tubular would go right on the rim of an 1898 bike. And the pre WWII riders in Newark rode Pye tubular tires that were probably as good as anything made since.

Joe Bender-Zanoni
Great Notch, NJ

----- Original Message -----
From: "Sheldon Brown"
To: ;
Sent: Tuesday, May 25, 2004 6:17 PM
Subject: Re: [CR]Requested Clarification: 700C & 27" / wheel & tire sizes /

framefit -- sorta for the less-experienced

> wrote:
> >Mr Collins wrote:
> ><Could someone clarify for me the basic distinctions between 27" and 700c
> >wheels? It seemed that in the discussions about 27" sew ups, there was
> >size
> >overlap. Might 700c wheels fit bikes made for 27" and vice-versa? I always
> >thought that to be impossible.
> That's generally so with older frames, there's only a 4 mm difference
> in radius (700c is smaller.) Newer, tight-clearance road frames
> won't handle 27 inch wheels, but any frame that will work with 27s
> will also take 700c, but you may have trouble getting the brakes to
> reach down low enough.
> >
> >Okay now, onward to the heart of the matter: I recommend checking
> >into Sheldon Brown's website for a thorough discussion of wheel and
> >tire sizing. He's been there and done that.
> Thanckx! is the place.
> >A very precise way to consider tire and wheel size is to measure the
> >diameter of the "bead seat area"--where you'd stick the glue if
> >you're considering a rim for tubulars, or literally where the bead
> >goes for a "wired-on" (clincher) tire. The imprecise, shorthand way,
> >popular over the years (check into 1950s UK cycling magazine ads)
> >was to speak of the nominal outside diameter. In reference to
> >lightweights, one would speak of 27" sprints (i.e. 700C tubulars,
> >because the outside diameter of a 700C tire and wheel is about 27"),
> >and 28" which meant 27 x 1 1/4 clinchers--28" being the nominal
> >outside diameter.
> I think this is not correct. There are two sizes that I know of
> being called "28 inch":
> 1. The 635 mm size, used on rod-brake roadsters, typically marked "28 x 1 1/2"
> B. The 622 mm size, most commonly known in English speaking countries
> by it's French designation "700C" is commonly called "28 inch" in
> northern Europe. This is commonly designated with two fractions, as
> in: "28 x 1 5/8 x 1 1/4."
> I have never known of anybody calling the 630 size "28 inch" and I've
> never heard of a tire in this bead seat that was anywhere near that
> large an outside diameter. (The 622 size, though the rim is smaller,
> exists in a much wider range of widths, up to 47 mm, which is close
> to 28 inches at the tread.)
> Sheldon "Ti/yres" Brown
> Newtonville, Massachusetts
> +-------------------------------------------+
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> | -- Will Rogers |
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