Sup peoples!

I'm close to finishing the restoration of a 70s Peugeot UO-8, all I need is a seat post..

The diameter of the tube holds a quarter (US) snug. I've attached a pic,



if anyone can help me figure out which seatpost measurment (mm) I need I would be extremely thankful!

Preeeeeeesh.

A US quarter is 24mm, which is a seatpost size I have never heard of.

It's probably a cheap steel open pipe post that fits in the insert you can see in the pic. Remove the insert and measure the inner diameter of the seat tube. You might get better info on this in the C&V forum.

FWIW, I have two 1970s French bikes, and they variously take a 25.0mm post (Gitane Interclub) and a 25.4mm post (Mercier 100), but the Peugeot could be different.

it looks like there's a shim in there...

French bike seatposts are a pain in the ass to get a replacement proper fitting seatpost.

You can always find one online, find the exact same model (perhaps even the same year), or have one custom made at a machine shop.

I made my own custom seatpost for my UO8

it needed to be 25.4

Thanks, you guys are always a lot of help, I'll be sure to post my findings asap, along with pictures of the finished project.. she's lookin good if I may say so myself!

https://www.sheldonbrown.com/seatpost-sizes-m-z.html#p

eot

Off topic...but make sure you aren't using an AVA stem.

I bought an origin 8 stem. If you sand it down, you have no problem at all

not AVA but I bought a schwinn 21.1mm quill off ebay a while back, looks structurally similar to the AVA. what i WAS unaware of is that the AVA has another name..the "death stem?" i'm thinking of all the places I wouldn't want ANY bike component to fail on me.. likeeee...here:

man, would that blow. x_x

Yeah man I have a blue U0-8 which came with an AVA death stem. They're notorious for snapping. Mine also came with cottered cranks, which were shot, but that's an entirely different issue.

The correct size is 25.4. I've bought a couple of them on eBay.

W/O the spacer/shim?

it makes sense that the diameter is 25.4mm without the shim because the diameter of a quarter (shown in the picture above) is 24.6mm. Can those shims just be hammered out? I'm slightly hesitant to use lethal force on my old lady. :/

You can probably just pry the shim out using a small flat blade screwdriver placed between the top of the seat tube and the bottom of the shim extension outside the seat tube. You should be able to find a plethora of 1" BMX seatposts that'll fit, since 25.4mm = 1". You can trust Grand Bois 100% on this as he totally knows vintage Peugeots.

yeah, I believe him for sure, can't argue with simple logic! I'll give the pry method a go when I get to the bottom of this beer. Thanks for the help comrade!

Hahaha turns out it was my fresh paint job making it seem like the thing was cemented to the tube.
I pried it out in 30 seconds flat. The shim is in great shape too so I'm gonna hold onto it.
Any idea why shims are used on seat posts to begin with?
My best guess would be the 22mm post is slightly lighter?

The seat tubes on many Peugeots are not well finished and the shim is an easy solution to this and some would also assert that the shim prevents the seat post from binding due to corrosion.

Well, Shim Shimmery Shim Shim Sharoo!

My PA10 has the same tubing as a UO-8, but never had a shim. I see no logical reason for the shim, despite what Sixty Fiver says.

Try Kalloy,
They still make some odd sized seat posts for older bikes

Yes, they do. See post #3. I have a 25.4mm Kalloy on my Mercier 100. It looks kinda like an old SR Laprade.