Hi Michael, If possible, I'd take a caliper measurement of both the post outer diameter and the seatube inner diameter to be sure if either (or both) are slightly out of spec.
Going up 2mm would not likely work in your favor if the seatube is spec'd correctly at 26.8. I also wonder if the binder bolt and nut could be contributing somehow and binding or somewhat cross threading? Riv seatbinders take easy to find metric bolts so you could try an alternate of the same size. Out of curiosity, do you notice the ears of the seatlug binder pinching or deforming such that they get close to touching and bridging the gap when tightened enough to hold the post sufficiently? Wondering as I have experienced too small posts before (not posts manufactured out of spec... but undersized posts that had been used on frames designed for larger diameter posts.) One was a hand-me-down frame that came into my possession with a 26.2 installed and a heavily deformed seatbinder. This frame turned out to require a 26.8 post after spreading the binder back apart and the 6mm difference was significant and easily noticeable. On the other hand, another frame called for a 30.9 post and the stock post was too short for me. I had a much longer 27.2 post and a 27.2-30.8 shim available and the 1mm difference of the 30.8 shim vs 30.9 seatbinder was minimal enough to not cause any noticeable deformation but definitely noticeable when tightening since it required much greater effort to get it nice and snug. Brian Cole Lawrenceville NJ On Monday, March 26, 2018 at 11:44:36 AM UTC-4, Michael Doleman wrote: > Just wanted to get some advice, here. > > I am building my new Sam Hillborne, which takes a 26.8 seatpost. For the > size of frame I use, unless I get a ridiculously short stem (like, 6cm), I > need a zero-setback seatpost. Especially if I want there to be space behind > the saddle to use my Carradice Bagman uplift. I tend to like the feel of a > zero-setback post, anyway, though. > > The only really nice, zero-setback post that I know of, in a 26.8 size, is > Thomson, so that's what I got. It looks great on the bike, but -- man -- > does it ever seem a bit narrow in diameter. I can tighten it down such that > it does, indeed, seem to be properly static in the slot, but I *really* > have to tighten the bolt down hard. Enough so that I'm slightly worried > about it and wanted to know if anyone else has had similar experiences with > Thomson posts. I can almost imagine that sizing-up, to a 27.0, might > actually work, but then I'd be worried about it getting hopelessly stuck. > > Maybe I shouldn't worry, I guess. All things being equal, I think I'd > rather have a seatpost that's a little too tight than a little too snug. > > Anyone have any words of advice and/or reassurance? > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscr...@googlegroups.com. To post to this group, send email to rbw-owners-bunch@googlegroups.com. Visit this group at https://groups.google.com/group/rbw-owners-bunch. For more options, visit https://groups.google.com/d/optout.
