Paramount seatpost diameter

[pach]

I have an 1991 Schwinn Paramount series 5 road bike frame (Japan). I wonder if anybody would know what diameter seatpost I would need. I tried my 27.2 mm but it seemed to big.

[Niflheim]

Sheldon Brown's database says yours is supposed to be a 27.4-but you said a 27.2 is too big not too small as would be expected.

I have a 26.8 on a Schwinn Super Sport. If your '91 is Chromoly instead of Aluminum, Schwinn may have used common seat tubes and it might be
26.8. If, nothing else, you could get a slighty smaller seatpost and add any necessary shims.

A more likely thought, maybe after 12 years your clamp has just constricted the seat tube down, especially if someone had an undersized seatpost fitted by constriction. Could try spreading it a little and maybe you would get your 27.2 in.

[Niflheim]

Sheldon Brown's database says yours is supposed to be a 27.4-but you said a 27.2 is too big not too small as would be expected.

I have a 26.8 on a Schwinn Super Sport. If your '91 is Chromoly instead of Aluminum, Schwinn may have used common seat tubes and it might be
26.8. If, nothing else, you could get a slighty smaller seatpost and add any necessary shims.

A more likely thought, maybe after 12 years your clamp has just constricted the seat tube down, especially if someone had an undersized seatpost fitted by constriction. Could try spreading it a little and maybe you would get your 27.2 in.