YABD - vintage Bernard Carré frame, etc

[enkei]

Excellent points, as usual. Thanks!

What dia is the odd seat post you're offering?

(06-08-2024, 04:51 PM)Jesper Wrote:  Super; answered above and beyond the call of duty! Thanks for the explanations. And yes, I will suck on an egg or two; because I've not eaten yet.

I did kind of gather that is multipurpose in design. Many of my Italian frames with fender mounting are similar but a little bit tighter in the rear geometry. I can certainly understand that adequate spacing for rear fender would require that longer c-stay. My c-stays on a similar frame are about .5-1 cm shorter; pure racers about 39.5 on the really short side (no aero seat tube or recessed wheel design) up to 41cm max for frames of that era or newer.

Very nice seat cluster treatment.

My comment about about the rear fork conjunctions relates to
the brazing work consistency. It may be excess paint, hard to tell without seeing it bare.

I am surprised a little by the post diameter (I was thinking more like 26.8mm), but I have no Vitus 971 steel frames to compare it with. Make sure the clamp binder slot is not closed up. I find it very common on older bikes that a smaller post gets installed for whatever reason and the seat lug is just tightened up until the oost won't slip. Usually it is just .2mm for the next smaller size, but still not uncommon for 2 sizes smaller. I have bought a frame and a separate post based on a seller's description only to find that the size is wrong and I get stuck with a smaller post I cannot use, all the while having the correct size once I reformed the seat lug to its orignal size. I did want to know what the post make was; just curious. I may have a nice one I could donate gratis since an odd size for compared to the frames I deal in (26.8mm to 27.2mm).
Thanks for the extra effort; and patience dealing with my queries.

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Jesper, I cannot thank you enough. This isn't just invaluable, it's super interesting.

My hunt for a suitable 26.6 has begun!

(06-09-2024, 02:49 AM)Jesper Wrote:  I did some research on the Vitus 971 seat tube specs. For the unbutted section at the seat lug it would be 28mm OD with .6mm wall thickness with 1.0mm wall thickness at the butt for a metric tube; ref. Vitus tubing chart. That gives us 28mm - (.6mm +.6mm) = 26.8mm ID for the seat tube at the lug barring any reaming of the tube. Allowing for .1mm each "side" of the seat post (.1mm +.1mm) provides for a 26.6mm seat post OD 26.8mm - .2mm = 26.6mm. which is more along the lines of what I thought a metric tubing lightweight bike would have for. Standard Vitus 28.6mm OD tubing has the same wall thickness so 28.6mm - 1.2mm = 27.4mm ID; 27.4mm - 2mm = 27.2mm OD seat post which would be very common.
Now the curveball; per a very experienced bike builder in the 70s, he states that most French bikes made with that 971 tubing (e.g. Gitane) came with 26.4mm OD posts, but they should have been 26.6mm given the tubing used: "A properly rounded and reamed SV 971 metric diameter seat tube should take a 26.6mm seatpost, 28mm OD - 2x .6mm = 26.8mm with .1mm clearance room per side. Most SV 971 bikes you see will have a 26.4mm seatpost."
He states the same thing I do; but of course he was observing these bikes at the time they were being made and so I certainly believe that he saw these 971 a frames being provided with the incorrect posts direct from the manufacturer. I did see where he stated why this was being done due to the lugs being so out of round that the manufacturers used improper posts instead of rounding out the seat lug. He states having an early 70s Vitus framed (not 971) bike coming with a 25.8mm post that should have been 26.4mm for it's tubing type. Also, his shop at times used a special mandrel to reform the top of the seat tube and lug.
I have had to do similar work using old posts where I tapered the ends and slowly inserted them by ever increasing diameters in order to reform the lugs and tubing. I would suggest that you try something similar since your frame requires a larger post than what is installed. This will prevent having to tighten the binder more than it should be and avoid any additional stress. One benefit if your frame is it having semi-wrap stay caps which in this particular instance are less likely to have a weakened joint than a stay cap side brazed only. Apparently in your case the post may be the original one installed, or it may be a replacement matching the original's size even though the original post was too small was too small to begin with. It still may be that a smaller post was used as a replacement due to difficulty caused by using the correct size. I would make things right; but your bike, your call.
Your bike weight sounds correct given butted tubing and being metric tubing (smaller diameter) than standard tubing. It certainly could be lightened up a bit; but I would try to keep it OE except the post. Even if the post is OE it might be a generic one. I would think it came with a Simplex Super LJ given the other Simplex components, but I think those posts only came as steel items.