Need advice - seatpost past minimum insert

[joseelias]

@Ian Raleigh

If I identified correctly there seems to be a small bump just above the lug in the back and some type of volume seen in a variation of the shadow tone on the left of it. I don't know if I saw it, but at least I think so.

Did you weld a new seat-post extension or did the frame stayed just like in the second picture?

 

[al-onestare]

@half cog and mynchiboy (and others too)
But if the bottom of the seatpost is under the bottom weld of the top tube, what difference does it make for it to be longer in terms of the frame?

Considering that the seat-stays support the backward movement of the seatpost (no matter the length), and the area of the seat-tube under the top-tube welds stops the movement of the bottom of the seatpost forward, what would be the advantage to have a longer post?

Unless the frame just under the top-tube is weaker than a lower part for supporting the pressure of the bottom of the seatpost, or it deforms a lot allowing for the seatpost to bend more than if it was inserted deeper even if it had the same exposed length, I'm having some trouble visualizing the reason why a longer seatpost offers an advantage for the frame.

These are honest questions. I'm just trying to understand the mechanics/physics of it.

As for my height I'm 1,85m (I guess +-6' 1") and my inseam 87cn (+-34.25").

I think I' have proportionally longer limbs (?). So I think my height may place me equally between a 19" and 20" frame but maybe my legs may really be better for a 20" frame?

@FluffyChicken
I understand what you're saying about the shims. They are short and unless the seat-tube barely extendeds the top-tube the bottom of the shim would not even reach the welds in the bottom of the top-tube.

**************

Here are some images of the bike with the 400mm post that snapped the clamp.

I beg the purists for clemency, but in my defense I've had to keep the bike functional since it's to only one I've owned in about 20 years.

As others have alluded to, I'm pretty sure a 19" would better suit you. The top tube length is ever so slightly longer, not enough to cause an issue. I realise that's tricky with your location but it's defo worth looking into if you can.

 

[Ian Raleigh]

@ Ian Raleigh Did you weld a new seat-post extension or did the frame stayed just like in the second picture?

No I left the frame as in the picture, the original extended seat tube was the actual seat tube and not a bit brazed on, such extensions was the norm' on 1980's road bikes :facepalm:

What it looks like now

 

[joseelias]

@ Ian Raleigh Did you weld a new seat-post extension or did the frame stayed just like in the second picture?

No I left the frame as in the picture, the original extended seat tube was the actual seat tube and not a bit brazed on, such extensions was the norm' on 1980's road bikes :facepalm:

What it looks like now

Very nice.