Thanks for the data, Scott. Unfortunately, I don't think it helps me. I'm guessing that what I need is the 19mm bolt. I believe the Campagnolo bolt would work well, but they're not keyed (right?) and have a reputation for breaking.

I haven't tried it but I have worked on a couple of bikes where people had managed to some how thread in the wrong cup. I have no clue how they managed to do it. At this point nothing I see done really surprises me about French bikes and BB.

I'm sure this is just a case of the correct (and original) cup being cross-threaded.

Justin. The dimensions I gave you are from the original equipment bolt. The one that came on my TdF.

And, not recommending a standard Campy bolt. I'm using one of those ones with the quick release lever on it? Ever seen one?
No one could break one of those. I actually don't know why I've got it on there. Figured maybe I remove my saddle when I went into the store ????

Yes, I understand what you're saying. I wouldn't consider using a QR bolt. Thems fer MTBs, man!

I don't doubt your measurements, but I think 30mm is much too wide this particular bike's seat lug. I had a 22mm (or maybe it was 25mm) and it bottomed out.

I was referring to the Campagnolo binder bolt on which one side is knurled. You use two 5M allen keys to tighten it.

Yeah, and they must weigh a half a pound! And I was musing the other day why my Gitane seems so heavy.

Oh, OK...I'm sorta slow on the uptake here...so you were asking the length of the non-original binder bolt on this Tour de France? Of course, mon ami, if it is indeed not a TdF, but an SC, the Campy might be original equipe', no? A "keyed" Campy binder bolt?
I'm lost.

Anyway, I have a Campy bolt here with one side knurled, standard 8 mm binder from that period, and yes, it's 20 mm in the fully closed position. Tightens in the ears of my TdF well, with a couple threads to spare.

Thanks for the inspiration. Just saved me a half a pound. I never ride that bike to the store anyway.

That's helpful, Scott! If the space is 20mm between the inside of the bolt heads when fully closed, then my guess on the 19mm bolt was right. Thanks!

I'll post pics this evening of this aberration including the seat lug. You may want to wear welding goggles as this build may be NSFF (not safe for Francophiles).

And to clarify:

Top: Common "keyed" binder bolt
Bottom: Campy "knurled" binder bolt

I have at least 3 frames with knurled Campy bolts in Keyed holes. It has never been a problem. My Gitane happens to have a T.A. bolt.

Pretty funny. I was wondering,"why on earth does he want to put in an original binder bolt?" That was, without a doubt, the most butt-ugly of the components on my TdF. The first thing I removed. A homely zinc plated horror with a huge nut. So I hung that big, chromed Campy quick release monster on there 'cause it never occurred to me to put the petite Nuovo Record one on. Until now.

Franco-friendly or not, Colonel, I look forward to seeing what you come up with on this one.

I've worked on a few bikes where the knurled Campag binder nut would just rotate in the clamp ear because the sizing wasn't spot-on.

I always remove the nut and clean the surfaces, the put it back in with a drop od RED LocTite and secure the bolt.

So far, these nuts never needed 2 Allen keys to tighten after that.

I worked on my "new" 1972 Nishiki Kokusai last night, and the solid binder bolt is keyed only into the separate centerpull brake cable hanger.
I have to adjust the hanger angle and hold it from rotating while I tighten the 12mm hex nut.
I think that a normal 6mm Allen key binder bolt would not try to move the hanger so forcefully, but for now I'm happy to keep this one stock.

On this note I will add, Colonel, at the risk of confusing myself further ... that I did try TWO different Campy 8 mm binder bolts when I dove into the dungeon to pursue your query. Neither of them exhibited the phenomena mentioned here by dddd, but the slightly newer one, circa mid 80's or so, with the more pronounced knurling, didn't want to fit in the ear well at all, and given their penchant for snapping, I didn't push it. But the older NR bolt seemed to snug in and grab pretty well. Only used one hex wrench.

The loctite isn't a bad idea, dddd.

My Gitane had this T.A. when I got it. I can't say if it's original.

I had 1st generation Dura Ace brakes on it for a while, but they seemed out of place.

I'm not sure these bars will stay, but I want to give them a try. Once the BB arrives this will get an old NR crankset with 50t track ring, a 19t cog and a SRAM PC-1 chain.

My metric Reynolds Jeunet, 63cm, is very flexy, but I like it, it makes for a very supple ride. But I'm only 160 lb. If I were heavier, the frame may feel too flexy. The bike doesn't make the best porteur, however, since the extra weight exacerbates the flex.