Originally Posted by thirdgenbird10211866
I bought my girlfriend a late 80s Bianchi Classica...i believe its strait guage tubbing...anyway, the seat post in it measures about 26.4 with my calipers but the stem that came in it was the wrong size, so who knows if this is right. (the binder looks correct) any guesses to what it should have??
Your Classica is early 1980s. It has the Piaggio decal, indicating it is no newer than 1984, which would be my guess, based on the decals. Please submit the serial number for my database.
The tubing is plain gauge (non-butted) manganese alloy. But this is only in the main tubes, The stays and original fork are hi-tensile steel.
As previously stated, other samples using this tubing have turned up with 26.4mm seat posts. It is certainly in the ballpark for a plain gauge, manganese alloy tubeset and there is no reason not to believe that it is correct.
I think you have done a very nice job in modernizing the Classica. It may be a bit overdressed, but provided the girlfriend likes it, it is well worth the investment.
Originally Posted by
EjustE
Tight is the way you want to fit a seat post (with a lot of lube on it)...
Ideally, a seat post should be a line fit, which means the size of the post does not exceed the inner diameter of the seat tube. A tight fit will mar the post during insertion, removal and adjustment, even with lubrication. The post should be the same size as the inner diameter of the seat tube or 0.2mm undersize. A lubricated post should slide easily into the seat tube.