"Always"? That's a pretty long time. https://www.sheldonbrown.com/seatpost-sizes.html
I own 15 theoretically buildable/rideable steel framesets (3 Follis, 2 Raleigh, 2 VooDoo, 1 each Bertin, Bianchi, Lambert, Mercier, Peugeot, Schwinn, Trek, a no-name frame that I suspect to be Tim Neenan, a Santa Cruz builder who went on to design the Sequoia at Specialized). The age range is 1950-1999; the tubing includes house brands (Peugeot, Mercier), Reynolds 531, Columbus SL, Tange (the VooDoos), Vitus, Durifort, Accles & Pollock and Trusty. The seatpost diameters range from 25.4-27.2. While the largest pool is at 27.2 (1988 Bianchi Superleggera, 1974 Schwinn Paramount, the Neenan, 1999 VooDoo Hoodoo), there's a pool at 26.8 that's nearly as large (Lambert, 1969 Raleigh Competition, 1995 VooDoo Hoodoo). The two French gaspipey bikes from Peugeot and Mercier are both 25.4; the Peugeot is a thickwall 50s 650B townie frame, while the Bike Boom Mercier has a sleeve for a cheapy steel seatpin that I haven't tried to extract, so I don't know what the real seatpost size is. In general, my older French frames are either gaspipe with 25.4, metric Reynolds 531 at 26.4, or non-Reynolds name brand tubing with 26.0-26.2. In Imperial tubing, DB Reynolds/Columbus/Tange is 27.0-27.4; straight tube Reynolds is 26.4-26.8. Even then, it depends on the build environment. Did the frames come off a production line, or were they made by individual craftspeople? How much time did they have available? Better-quality frames made by skilled builders out of better-quality tubing usually have larger diameter seatposts, because the frames use stronger tubing which can have correspondingly thinner walls, so there's a wider diameter for a setapost. If the builder has more time, they can ream the seat tube out to fit a larger seatpost (Waterford does this as a general practice, which is why their standard seatpost for 531 frames is 27.4). But on a production line (Schwinn, Raleigh, Peugeot, Gitane etc) where the principle was to get the bike down the line, the seatpost-install guy might try to fit the theoretical "ideal" seatpost (say 27.2, for Imperial Reynolds 531 DB), find that it doesn't fit (maybe due to distortion in the seat cluster by the heat of the brazing, or maybe the torch guy accidentally flipped the seat tube upside down and the thick part is at the seat cluster instead of the BB shell), and so they stick a 27.0 seatpost in, quick and dirty. Get the product down the line! That's my suspicion as to why my 1984 Trek 720 (Imperial Reynolds 531c DB) has a 27.0, instead of the 27.2 post in the specs. So, the size of the seatpost is the size that fits the frame, unless somebody chooses to do something special to the frame. Probably the biggest reason that the industry treats 27.2 as a de facto standard now is because of several decades of oversize tubing aluminum frames, where a 27.2 seatpost will fit into tubing that's already got thick walls. Peter Adler Berkeley, CA/USA On Monday, October 18, 2021 at 8:57:16 PM UTC-7 fraze...@gmail.com wrote: > Yeah, when I finally made the decision to actually buy a Rivendell instead > of just lusting after one...I was actually surprised that the frames aren't > spec'd with 27.2 seat tubes...its always been kinda the unofficial size for > steel frames. > > It's Grant though, so.... 🤘 > -- 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 view this discussion on the web visit https://groups.google.com/d/msgid/rbw-owners-bunch/606b3c4e-93f6-43e4-93bf-6ae8c4435577n%40googlegroups.com.
