Peugeot Ventoux 501 seatpost - 26.0 or 26.2mm?

[Ugo51]

Hi guys,

Old Peugeot frame made with Reynolds 501 tubing had 26.0 or 26.2mm seatpost?

Thanks

 

[tagnut69]

Quite possibly 24mm

 

[Ugo51]

Those were the Carbolite frames.

This is definitely 26.0 or 26.2 but as the lip of the seatpost is a bit damaged I can't quite take an accurate measurement.
So if anyone could confirm I would feel more confident before buying a seatpost

 

[LondonClassic]

My Triathlon with 501 is showing as 26.2 if that helps (OEM Stronglight fluted seatpost). Same era as your Ventoux.

 

[Ugo51]

Thanks.
I was leaning more towards it being 26.2 so this is a nice confirmation

 

[Ugo51]

Update: I machined a seatpost down to 26.2 (26.14, to give it some tolerance) and doesn't fit.
So maybe it's a 26.0!

 

[bikeworkshop]

Check the sides of the slot between the clamp bolt are parallel.
A lot of older frames have been used with too- small a post.

When the tube is distorted, trying a new post is best. We have dozens of used ones so can try them out - measuring rarely works, and the park drop-in tool isn't much better - although both can get you in the ballpark.
Once you're close, you can feel the difference between 0.2 and 0.4 mm slop - but some frames the internal dimensions are varied, or the tube wasn't reamed after brazing, so the "correct" size sometimes doesn't fit .

26.0 is quite common, next size down that's common is 25.4 - but the French were always metric-oriented so I'd go for 26.

 

[Ugo51]

I agree. At this point is almost surely 26.0
I doubt it's as little as 25.4
I'll try the 26.0 seatpost today and see how it goes.

 

[Ugo51]

The 26.0 doesn't fit either!
The outside diameter is 28.1 though, and the wall thickness is 0.9 which checks with the ID being 26.2 at the top. I can't imagine what kind of distortion might have caused the seatpost to shrink just below the top...
I can fit up to 25.6 comfortably, 25.8 doesn't fit.

Tomorrow with better light I'll try to take a photo of the inside