Interesting post Chas, thanks.
Regarding it being a somewhat common build trick to use the thicker wall Reynolds 531 seat tubes in 70's English bikes. Many 70's Ron Coopers indeed seem to be this way (27.0 post), in sizes 58c and larger. Versus a 27.2 in 57c and below. Sheldon Brown agreed this was intentional (tubing selection). I've noticed this on several of Ron's frames. With Ron being very meticulous in both design and execution, I expect it is intentional, and the thicker tube was used.
Bill Roberts Jacksonville, Oregon USA
>
> Message: 9
> Date: Sat, 17 Apr 2010 14:08:22 -0700
> From: verktyg <verktyg@aol.com>
> Subject: Re: [CR] Falcon Professional
> To: gobr@blueyonder.co.uk, Classicrendezvous@bikelist.org, Bob Freitas
> <freitas1@pacbell.net>
> Message-ID: <4BCA2346.7000405@aol.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> During that era Reynolds offered their 531 seat tubes with the following
> wall thickness dimensions:
>
> BSW Gauge (the British Standard for tubing also SWG Standard Wire Gage)
>
> 22/24, 21/24, 20/23 and 19/22
>
> the rounded off metric equivalents were:
>
> 5/7, 5/8, 6/9 and 7/10 meaning 0.5mm wall thickness in the thin section
> at the top of the tube and 0.7mm at the bottom and so on.
>
> These were also listed as the actual "nominal" dimensions, .7/1.0mm and
> so on.
>
> These tubes were made in both metric 28mm and Imperial (inch) 28.6mm
> outside diameters.
>
> The thinner 5/7 size tubes came in 531SL sets (and 753) Reynolds 531P
> sets and others used the 5/8 tubes.
>
> Reynolds would supply any combination of tubes as long as you placed an
> order for at least 100 sets so you will find lots of variations.
>
> 7/10 and 6/9 were the most commonly used wall thicknesses found in
> production bikes.
>
> Theoretically a 7/10 wall thickness inch size seat tube would use a 27mm
> seat post and a 6/9mm tube, a 27.2mm post.
>
> That's assuming that the seat tube is round to the proper size to begin
> with.
>
> The high heat involved in brazing on the seat stays and creating a
> fillet where needed frequently warps the seat lug and can cause the tube
> to bulge inside the lug. Also not all seat lugs were round to begin with!
>
> I had a set of homemade steel mandrels that I used to use to round out
> seat tube IDs. By gently hammering in the smallest size that almost fit
> the ID and then working up from there until the seat tube was close to
> round.
>
> Once near round the seat tube could be reamed to the closest standard
> seatpost size.
>
> These are bikes not Swiss watch movements. It's very difficult to
> economically produce accurately dimensioned tubing. Most "precision"
> tubes are resized after the drawing process by running them through
> angled rollers or centerless grinding the tubes to the specified OD.
>
> If you take side to side and front to back or top and bottom
> measurements of bike tubes about 4"-5" (100mm - 125mm) from the lugs you
> will frequently find that the tubes are not round!
>
> BTW, add 0.1 to 0.2 to the diameters for paint thickness.
>
> Another thing, seatposts are not always round or true to the marked
> size. I have a NIB 26.6 Campagnolo NR seat posts that measures 26.5mm to
> 26.7mm depending on the location on the post. Also most used seatposts
> have been sanded and or polished at some time in their lives. This
> leaves them slightly undersize.
>
> 2nd BTW, Columbus SL had 6/9 wall thickness and SP was 7/10.
>
>
> The Prugnat or Bocama lugs with the factory stamped cutouts didn't
> appear until the mid 70s or later. This would place the frame at 1975 or
> 76 at the earliest. These lugs were more common in the late 70s and 1980s.
>
> The Cro-moly sticker looks similar to ones used on some Japanese bikes
> in the 1970s.
>
> Chas. Colerich
> Oakland, CA USA
>
>
> Giles O'Bryen wrote:
> > Marten, do I take from your reply that Reynolds did make a 27.0
> seat tube
> > that was slightly thicker than the 27.2?
> >
> > Barrie, I am sure the frame was not built for a professional
> rider -- it has
> > a decal saying Professional across the top tube, that's all!
> >
> > Forgive my ignorance, but what is an FKW?
> >
> > Giles O'Bryen
> > London UK
>
>
> ------------------------------
>
> Message: 10
> Date: Sat, 17 Apr 2010 17:20:18 EDT
> From: FujiFish1@aol.com
> Subject: Re: [CR] 50's Frejus tubing material
> To: classicrendezvous@bikelist.org
> Cc: johnprochss@yahoo.com, avartist@gmail.com
> Message-ID: <1a34b.79eb8bd5.38fb8012@aol.com>
> Content-Type: text/plain; charset="US-ASCII"
>
> John, et al,
> If you want to check for Columbus tubing, which in its heavier
> form (like
> SP, and maybe early SL?) is often 26.8mm inside the seat tube ...
> just look
> for the five spiraled ribs at the bottom of the steer tube.
> Columbus was
> doing this at least as far back as the mid 1950s, as evidenced by its
> existence on my 1955 Torpado. Here's a look inside a 1984 steer
> tube, that I've
> posted in the past:
> <http://www.wooljersey.com/gallery/fujifish1/VintStuf/Parts/Spir
> alSLX01.jp
> g.html>
> Or, Tiny URL: http://tinyurl.com/
>
> Also, the steer tube will sometimes have a Columbus dove logo,
> or Reynolds
> along with tube size stamping visible, albeit, often very faint.
>
> BTW guys .. have you forgotten that Dale asks us to sign off with our
> country too? This is for the benefit of list members from abroad
> that might
> not know our states off-hand. Sure, Texas is pretty well known,
> but it's a
> rule. Let's all save him some headache, if we can.
>
> Ciao,
> Mark Agree
> Southfield MI USA
> ~ ~ ~
>
>
> Date: Sat, 17 Apr 2010 07:14:35 -0700 (PDT)
> From: John D Proch <johnprochss@yahoo.com>
> Subject: Re: [CR] 50's Frejus
> To: Mike Short <avartist@gmail.com>, classicrendezvous@bikelist.org
>
>
> Hi Mike,
>
> You are possibly right.
> I am still searching. Seat tube fits a 26.8 post.
> Thanks,
> John Proch
> La Grange, Texas
>
>
>
>
> Sent: Sat, April 17, 2010 9:05:55 AM
> Subject: Re: [CR] 50's Frejus
>
> Hi John,
>
> Might Falck tubing also be a possibility?
>
> Mike Short,
> Austin Texas.
>
> On 4/17/10, John D Proch <johnprochss@yahoo.com> wrote:
> > Hello Vintage Cyclists,
> >
> > What frame tubing brand were Frejus built with from the late 40's
> > through the early 60's? Columbus or 531?
> >
> > Thank you,
> > John
> > Proch
> > La Grange, Texas