Advertise on Bikeforums.net



User Tag List

Results 1 to 10 of 10
  1. #1
    DRF aka Thrifty Bill wrk101's Avatar
    Join Date
    Jan 2008
    Location
    The NC Mountains
    My Bikes
    Too many to list, all vintage
    Posts
    19,204
    Mentioned
    46 Post(s)
    Tagged
    1 Thread(s)

    1975 UO8 Seat Post Size

    OK, I would like to purchase a replacement seat post for my UO8 rebuild. My measurement shows the current post is 26mm OD. But doing a search I see others say this bike had a 22 or 24.x seat post size.

    I bought this bike "new" (at least it was presented as such) back in 1975, and this is the original steel seat tube. Thoughts/comments appreciated before I possibly waste money on the wrong size post. To make it a little more confusing is that my AO8 (guessing vintage early 70s, I think it is older than the UO8) has a 22mm seat post with a shim. I have had the AO8 for about 20 years, garage sale find way back then. .


    Thanks!
    Attached Images Attached Images

  2. #2
    Senior Member Iowegian's Avatar
    Join Date
    Dec 2005
    Location
    Boulder, Colo
    Posts
    1,720
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Lots of shops have a graduated post that is inserted into the seat tube to measure the ID of the tube. This is probably the best way to determine what size post you need.

    Is there a marking on the current post? Lots of posts have the size engraved in them below the min insertion mark.

    Or just measure the current post with a good set of calipers. There are a lot of variations in old U08's so don't just go by what someone else has.
    Last edited by Iowegian; 01-30-08 at 08:59 AM.

  3. #3
    Old Skeptic stronglight's Avatar
    Join Date
    Jan 2006
    Location
    New Mexico, USA
    My Bikes
    19 road bikes & 1 Track bike
    Posts
    1,044
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    The various UO-8 variants from that era that I've seen all had 24.0 mm posts... and the shim insert just as you mentioned - with 1 mm thick walls... so 26.0 makes sense. I noticed that the shim on my last such bike did serve the function of spanning around a minor seam or weld inside the seat tube. So, maybe your bike simply had a nice smooth seat tube, had better seamless tubing than some, or was simply already cleaned out.

  4. #4
    Bottecchia fan
    Join Date
    Aug 2003
    Location
    Colorado Springs, CO
    My Bikes
    1959 Bottecchia Professional (frame), 1966 Bottecchia Professional (in progress...), 1971 Bottecchia Professional (frame), 1973 Bottecchia Gran Turismo, 1974 Bottecchia Special (in progress...), 1977 Bottecchia Special (frame), 1974 Peugeot UO-8
    Posts
    3,419
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I measured mine with a micrometer and it says 26.0 although I don't have seatpost that size to try out. Mine has the same shim/22mm post arrangement.
    1959 Bottecchia Professional (frame), 1966 Bottecchia Professional, 1971 Bottecchia Professional (frame),
    1973 Bottecchia Gran Turismo, 1974 Bottecchia Special, 1977 Bottecchia Special (frame),
    1974 Peugeot UO-8, 1988 Panasonic PT-3500, 2002 Bianchi Veloce, 2004 Bianchi Pista

  5. #5
    DRF aka Thrifty Bill wrk101's Avatar
    Join Date
    Jan 2008
    Location
    The NC Mountains
    My Bikes
    Too many to list, all vintage
    Posts
    19,204
    Mentioned
    46 Post(s)
    Tagged
    1 Thread(s)
    I will measure the tube with a micrometer (good idea). Seat post is tight, but I can get it in and out. The internal bore looks clean with no high spots. I don't see any markings on the seat post at all, it looks pretty generic, and is about 6 inches long. Thats probably one reason it fits. I can't imagine a 350mm stem at 26.0 fitting in. Not sure Peugeot had that much quality/consistency on an entry level boomer bike.

  6. #6
    feros ferio John E's Avatar
    Join Date
    Jul 2000
    Location
    www.ci.encinitas.ca.us
    My Bikes
    1959 Capo; 1980 Peugeot PKN-10; 1981 Bianchi; 1988 Schwinn KOM-10;
    Posts
    14,580
    Mentioned
    3 Post(s)
    Tagged
    0 Thread(s)
    For what it's worth, my 1970(?) UO-8 frame has a thin OEM shim and a steel seatpost with a 25.6mm outer diameter.
    "Early to bed, early to rise. Work like hell, and advertise." -- George Stahlman
    Capo [dschaw'-poe]: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger, S/N 42624
    Peugeot: 1970 UO-8, S/N 0010468
    Bianchi: 1981 Campione d'Italia, S/N 1.M9914
    Schwinn: 1988 Project KOM-10, S/N F804069

  7. #7
    Bottecchia fan
    Join Date
    Aug 2003
    Location
    Colorado Springs, CO
    My Bikes
    1959 Bottecchia Professional (frame), 1966 Bottecchia Professional (in progress...), 1971 Bottecchia Professional (frame), 1973 Bottecchia Gran Turismo, 1974 Bottecchia Special (in progress...), 1977 Bottecchia Special (frame), 1974 Peugeot UO-8
    Posts
    3,419
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by John E View Post
    For what it's worth, my 1970(?) UO-8 frame has a thin OEM shim and a steel seatpost with a 25.6mm outer diameter.
    John, is that 25.6mm post + the shim. I seems like several folks have posted various diameter seatposts with shims of varying thinknesses. Looks like Peugeot used whatever seatpost was laying around and shimmed it to fit. I'm going to try 26.0 in mine with no shim since that appears to be the size it measures out to.
    1959 Bottecchia Professional (frame), 1966 Bottecchia Professional, 1971 Bottecchia Professional (frame),
    1973 Bottecchia Gran Turismo, 1974 Bottecchia Special, 1977 Bottecchia Special (frame),
    1974 Peugeot UO-8, 1988 Panasonic PT-3500, 2002 Bianchi Veloce, 2004 Bianchi Pista

  8. #8
    feros ferio John E's Avatar
    Join Date
    Jul 2000
    Location
    www.ci.encinitas.ca.us
    My Bikes
    1959 Capo; 1980 Peugeot PKN-10; 1981 Bianchi; 1988 Schwinn KOM-10;
    Posts
    14,580
    Mentioned
    3 Post(s)
    Tagged
    0 Thread(s)
    Yes, the post itself is 25.6mm, with which I use a very thin shim. Your 26.0mm idea just might work, although it would require the tubing walls to be just under 1mm thick, based on a French outer diameter of 28.0mm. That sounds about right for Reynolds 531, but feels a bit thin for plain carbon steel.
    "Early to bed, early to rise. Work like hell, and advertise." -- George Stahlman
    Capo [dschaw'-poe]: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger, S/N 42624
    Peugeot: 1970 UO-8, S/N 0010468
    Bianchi: 1981 Campione d'Italia, S/N 1.M9914
    Schwinn: 1988 Project KOM-10, S/N F804069

  9. #9
    Bottecchia fan
    Join Date
    Aug 2003
    Location
    Colorado Springs, CO
    My Bikes
    1959 Bottecchia Professional (frame), 1966 Bottecchia Professional (in progress...), 1971 Bottecchia Professional (frame), 1973 Bottecchia Gran Turismo, 1974 Bottecchia Special (in progress...), 1977 Bottecchia Special (frame), 1974 Peugeot UO-8
    Posts
    3,419
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by John E View Post
    Yes, the post itself is 25.6mm, with which I use a very thin shim. Your 26.0mm idea just might work, although it would require the tubing walls to be just under 1mm thick, based on a French outer diameter of 28.0mm. That sounds about right for Reynolds 531, but feels a bit thin for plain carbon steel.
    Hmmm...time to bust out the old micrometer again...

    Edit: And the answer is: The OD of the seat tube is 28.0mm as expected. The opening at the seat lug is fairly round but the wall edges are not of uniform thickness and there is the slot cut in the back so it's difficult to get a precise measurement but does appear to be 26.0 ID. That could mean a 1.0mm thickness, straight gauge tube which would be reasonable I think even for an old hi-ten steel tube. A fairly heavy tube like Reynolds 531 Super Tourist was 1.0mm at the butt and 0.7mm in the middle being 1.0mm all the way through would be pretty heavy.
    Last edited by Kommisar89; 01-30-08 at 10:38 PM.
    1959 Bottecchia Professional (frame), 1966 Bottecchia Professional, 1971 Bottecchia Professional (frame),
    1973 Bottecchia Gran Turismo, 1974 Bottecchia Special, 1977 Bottecchia Special (frame),
    1974 Peugeot UO-8, 1988 Panasonic PT-3500, 2002 Bianchi Veloce, 2004 Bianchi Pista

  10. #10
    DRF aka Thrifty Bill wrk101's Avatar
    Join Date
    Jan 2008
    Location
    The NC Mountains
    My Bikes
    Too many to list, all vintage
    Posts
    19,204
    Mentioned
    46 Post(s)
    Tagged
    1 Thread(s)
    I ended up using a 25.8mm seat post that I got off of ebay. It was plenty tight. According to my micrometer, the one I took out was 25.9, and the hole is 25.85 to 25.90.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •