Early 50s La Gazelle - Eau-de-Nil 🛠️ The Merlot Aftermath 🍷

🛠️ Nerdy bike wrenching snippet - potentially useful information for other asylum members.

The handle bars have been cut in half. In part because I don't want anyone to rescue them from the tip and re-use them, and I also wanted to get an idea of wall thickness at the stem clamp area. Amazed to find that there is a steel 1.2mm thick sleeve internal at the bulge area. The aluminium appears 1.5mm thickness throughout. I have no idea how they made these. The short bulge area near the clamp is really only to stop accidental crushing / gouging by the stem; I don't think it offers any improvement to strength and stiffness like modern bars.
 
Not much progress lately except figuring out the right seat-post size. The old post is bent and ovalised, and while checking the seat-tube diameters it appears the top of the seat-tube just below the seat clamp cluster is slightly ovalised too. God knows how this happened but think it could be the dreaded over tightening of a bike stand or something. Hoping it won't be a serious issue and a new seat-post will work fine.

I'm pretty sure the tubeset is Vitus now; learnt that 28.0 mm seat-tube external diameter typically means a 26.2mm seat-post on older French bikes. Not at all the same as Reynolds 531 imperial or metric tubesets for example.
 
Woz said:
Not much progress lately except figuring out the right seat-post size. The old post is bent and ovalised, and while checking the seat-tube diameters it appears the top of the seat-tube just below the seat clamp cluster is slightly ovalised too. God knows how this happened but think it could be the dreaded over tightening of a bike stand or something. Hoping it won't be a serious issue and a new seat-post will work fine.

I'm pretty sure the tubeset is Vitus now; learnt that 28.0 mm seat-tube external diameter typically means a 26.2mm seat-post on older French bikes. Not at all the same as Reynolds 531 imperial or metric tubesets for example.
Click to expand...
Yes forgot to say I checked my two Vitus tubed frames both 26.2 👍
How far down is the seat tube ovalised?
Those seatposts are thin very easy to over nip the bolt might just be a combo of that and the post being reinserted in a different position and retightened? How much out of round is it?
 
Mickeyspinn said:
Yes forgot to say I checked my two Vitus tubed frames both 26.2 👍
How far down is the seat tube ovalised?
Those seatposts are thin very easy to over nip the bolt might just be a combo of that and the post being reinserted in a different position and retightened? How much out of round is it?
Click to expand...

Just had a little closer look and messed around with the verniers. About 30mm below the seat lug the seat-tube is "flatter" in the same plane as the wheels (ie. front to back). It's a bit hard to measure.

The seat-post diameter varies from about 26.1mm to 26.3mm - so a 0.2mm difference pretty much throughout it's short length. That's why I think the seat-post and seat-tube were clamped together. Am I being a bit OCD perhaps? I know this is 70 year old steel, but it feels out of tolerance and I really don't want to struggle with that seat-post again.

I'm leaning towards a more beefy seat-post, something not quite period correct and aluminium going forward.

It's not until about the mid 60s that saddle clamps started to disappear in favour of seat-posts with an integrated cradle for a saddle.
 
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