Thread: Legnano project
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Old 02-08-21, 04:17 AM
  #19  
oneclick 
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Fixed a flaw

There was a bit of the seat-tube that had become distorted to point where it was hindering (and if forced scratching) the seatpost. It's possible that this occurs in other Legnanos so details follow:

The bit that was distorted was the lower edge of the hole inside the seat lug. It had been moved inward; I can think of two possibilities

a) during manufacture if the hole was sized the metal have have bent out of the way instead of being removed; or
b) a misalignment of the seat binder bolt combined with over-zealous spanner application.

Here is a before pic; you can see the lip but the distortion isn't visible - but when felt it was clearly a small ridge, about a mm wide,
running around the periphery of the bottom edge (the sides and top were fine):




And here's how to fix it. Take a steel seatpost a bit smaller than the true size, and make a shim that will just take about up the clearance.
The post should have as much of a rounded or tapered bottom as you can find, and it should be a nice shiny chrome SMOOTH one.
My seatpost size is 26.4, I used a 25.6 post and an 0.60 shim, and after doing this the nice seatpost which is actually 26.35-ish goes in with no trouble.




Place the shim opposite the bent lip, insert the post, and apply hammer (you can just see the bottom edge of the post in the hole here).
I only had to do this once; after about an inch past the contact point it was well tight, needed a good grip with the pliers to get it out:



That steel tube was hard; it left these witness marks on the post (about an inch up from the bottom):


Last edited by oneclick; 03-18-21 at 04:55 AM.
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