Bicycle Mechanics - Seat Post confusion...

I posted this issue a while back in the C&V forum but I'm still stumped so I thought I'd try it out on you lot...

To make a long story short: I'm building up a '78 Raleigh Rampar R-1027 frame and have no idea what the correct seat post diameter is. I've tried a 25.6 and it seems loose at first but after a few inches insertion it gets pretty snug. I've also tried a 25.8 and it's really tight but I think I could get it in. Any of you have any knowledge about the Rampar's or have a suggestion for which size post I should use?

I can tell you this ... I just downloaded the '78 catalogue from Sheldon Brown's site, and ... conspicuously /absent/ is the seatpost dia from the r-1027 frame (D'OH!).

Got calipers??

I can tell you this ... I just downloaded the '78 catalogue from Sheldon Brown's site, and ... conspicuously /absent/ is the seatpost dia from the r-1027 frame (D'OH!).

Got calipers??

haha, yeah I downloaded the catalogue a while ago and found the same thing. I have some cheap plastic vernier calipers that I used to take a measurement, but I can't remember what my reading was. I even took my bike to an LBS and they told me the post diameter was 26.4- which i determined was way, way off after ordering a seat post in that size. I think the problem is that the seat tube tapers a bit. Is this common?

That site will not tell you, besides, you have both sizes on hand, better than reading words in cyborspace. I'd read your other post concerning this matter. Make sure the larger of the two is clean, use solvent or what's known as Crokus cloth, akin to emery cloth not sand paper, it's used to remove LESS than ont thousanth of an inch. I used to use it on wrist pins, bushings etc. as a machinist. To me though, it seems that the smaler of the two is more likely "correct". You'd stated in your other post of your suspecting that the top of the SP tube was expanded (swedged) , seems likely. Worst case with the smaller is that the post slips (not likely). Worst case with the fatter post is that it binds (very likely). I've had all this happened to me. I've seen you around here before so I won't state the obvious moreso than I already have. Seat post don't warrant the least bit of interence fit.

Thanks for the advice. I'm taking the frame to the powder coater this evening, and when I get it back I'll make sure the 25.6 is held securely when clamped- if so I'll just roll with it. I was leaning towards the 25.6 anyways- I'm just new at this and needed fellow forumites to nudge me in the right direction. Cheers!