What's the frame made of? If it's British then it's probably 27.2
Nothing wrong with reaming an old frame if needed.
I suspect that over time the slot on the seat lug has closed up slightly. Take a large flat blade screwdriver, insert it into the slot and gently open up the slot. Then try your 27.2 seatpost again, well greased.
What's the frame made of? If it's British then it's probably 27.2
Nothing wrong with reaming an old frame if needed.
I suspect that over time the slot on the seat lug has closed up slightly. Take a large flat blade screwdriver, insert it into the slot and gently open up the slot. Then try your 27.2 seatpost again, well greased.