Almost. As Laing said, the nominal rim bead seat diameters discussed are 584 mm, 622 mm, and 630 mm. The designations 650B and 700C (none for 27" rims as the former are a French convention and the latter English or American) correspond in fact to 584 and 622 bsd's. The 650 and 700 numbers refer to nominal overall rim diameter, the "B" and "C" (there are others) to what used to be tire widths; Sheldon does not specify the widths or the ranges but perhaps someone can fill this in.
27.5" and 29", like 26", refer to de facto, rough, overall wheel diameters when shod with "fat" tires, conventionally 2" or so. Thus a 27.5" wheel has a 650B rim with a fattish tire, and a 29er has a 700 "C" rim with a fatter tire than the original "C" width (but see immediately earlier). And of course 26" wheels are 559 bsd rims with 50-55 mm tires. You can find 650"B" tires as narrow, I think, as 32 mm, 700C tires as fat at least as the almost 62mm ones on one of my bikes, and "26" tires as narrow as an actual 22 mm on narrow 559 rims. Laing, you probably know this. Sheldon said it long before I did (and I cribbed from him just now): https://sheldonbrown.com/tire-sizing.html#french In particular: 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. (there are others of course). 584 rims build up into 650B wheels. On Mon, Oct 26, 2020 at 11:27 AM lconley <[email protected]> wrote: > 27" rims are 630 BSD > 700C (29") rims are 622 BSD > That is a diameter difference of 8mm which is a 4mm difference in radius - > so the brake pad position is just slightly more than 1/8 of an inch off. > The 27" is larger in diameter than a 700C (29"). > > 650B (27.5") is 584 BSD > > So a 27.5" rim is considerably smaller than a 27" rim. > > When talking about rim diameters, using the BSD (Bead Seat Diameter) is > the only reference that lets you compare relative diameters. > > There are more than one BSD for 26" rims. > Ditto for 20" rims. > > Laing > Delray Beach FL > > > > On Monday, October 26, 2020 at 1:16:13 PM UTC-4, Sam Perez wrote: >> >> Hi all I'm working on several projects at the moment, an old steel bike >> had 27 rims /tires in the late 2000's I laced the old campy 5s hub to 700c >> for more tire options. Just now I put an old 27 rim to see the difference >> since I was told 27 is 650b. To my astonishment the brakes lined up exactly >> with the 700c rim. On line there was conflicting information. With a 700c >> I fit a 35c tire I was hoping to transfer my hetre tires to this frame >> thinking the smaller diamiter would afford me a wider spot on the chain >> stays... Thoughts / advice. >> > -- > You received this message because you are subscribed to the Google Groups > "RBW Owners Bunch" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/rbw-owners-bunch/49b719bc-cff8-41ff-ab9b-05638ccc30a3o%40googlegroups.com > <https://groups.google.com/d/msgid/rbw-owners-bunch/49b719bc-cff8-41ff-ab9b-05638ccc30a3o%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- ----------------------------------------------------------------------- Patrick Moore Alburquerque, Nuevo Mexico, Etats Unis d'Amerique, Orbis Terrarum -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/rbw-owners-bunch/CALuTfgsxG54oZmCu%2BgUzmkr3duCht66MumVfQYD%3DWVm%3D%2Bqz3hQ%40mail.gmail.com.
