Re: wtf chain ring bolts

On 3/7/2025 9:56 AM, bp@www.zefox.net wrote:

AMuzi <am@yellowjersey.org> wrote:

>
"tubulars".*
>
They predate numerical designations but originally were
called 28 inch as they were a lot fatter then. Actual rim
diameter is 630mm.

 So the tire was named by major diameter x width and the wheel
by major tire diameter minus twice the minor diameter? That's
sensible. Provided the cross section is always circular. Is it?
 Thanks for writing!
 bob prohaska
  

Yes, modern ISO system bicycle tires describe (rough, nominal) diameter and (rough. nominal) width.
Take a tape measure to your "29x50" or "26x1.95" to see why I wrote those are rough and nominal dimensions.
Originally calling tubulars "28" sorta made some sense, but as popular tire widths became smaller the actual diameter dropped as well.
I have ridden a much cleaner example of this extremely well made and nice handling Pope Columbia shaft drive fixie. Note standard racing tubulars of the era:
https://www.worthpoint.com/worthopedia/rare-antique-pope-columbia-drive-shaft-bicycle
Compare current tubulars:
http://www.yellowjersey.org/PANAK7IB.JPG
Tubular tires from both bikes fit each other's rims.
The confusion all comes from an initial practice of describing tires by outer diameter, just like carriage wheels. As tire width fashion changed for each rim format, the nomenclature was stuck in a fictitious 'diameter'.
Modern systems for autos are more logical (not by much; they have their own foibles) by describing rim size rather than tire outer diameter. A 13" auto wheel has a rim 13" diameter at the bead set and (in my case) a tire 23 inches in diameter. We have a useful ISO bicycle system (useful because it works) but note a "29" rim and a "700" rim (same ISO of 622mm) are neither 700mm nor 29 inches.  622mm is about 24-1/2 inches.
--
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971