seatpost sizes

For discussions about bikes and equipment.
Hudson1984
Posts: 213
Joined: 21 May 2012, 2:02pm

seatpost sizes

Postby Hudson1984 » 3 Feb 2020, 1:56pm

So, new frame has arrived - but I need a seatpost...what sizes to they come in, just want to sence check what I see on the tape measure is correct.

thatsnotmyname
Posts: 595
Joined: 23 Jan 2020, 10:23am

Re: seatpost sizes

Postby thatsnotmyname » 3 Feb 2020, 1:59pm

They come in a multitude of sizes, but 27.2 is fairly common. Would be much easier to search by brand and/or frame type.

Brucey
Posts: 42324
Joined: 4 Jan 2012, 6:25pm

Re: seatpost sizes

Postby Brucey » 3 Feb 2020, 2:51pm

check what size it should be with the manufacturer of the frame, or get it measured properly. If you are even 0.2mm out it can ruin the frame.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Hudson1984
Posts: 213
Joined: 21 May 2012, 2:02pm

Re: seatpost sizes

Postby Hudson1984 » 3 Feb 2020, 2:54pm

https://www.wiggle.se/battaglin-c12-plus-veloce-2012/

that's my bike (except I'd have red where they have white)

so looks to me 31.6 - that's what i've now ordered :) cheers all, happy I didn't buy the 32.0 I found

User avatar
Mick F
Spambuster
Posts: 50718
Joined: 7 Jan 2007, 11:24am
Location: Tamar Valley, Cornwall

Re: seatpost sizes

Postby Mick F » 3 Feb 2020, 2:55pm

thatsnotmyname wrote:They come in a multitude of sizes
Brucey wrote:check what size it should be with the manufacturer of the frame

Spot on on both points.
Mick F. Cornwall

User avatar
Mick F
Spambuster
Posts: 50718
Joined: 7 Jan 2007, 11:24am
Location: Tamar Valley, Cornwall

Re: seatpost sizes

Postby Mick F » 18 Mar 2020, 10:25am

Dawes Lady Galaxy. 531 main tubes.

Stripping and checking it out, and taken the non-original seatpost out. Came out easily.

Looking at the post I see it's 26.2mm diameter, and looking at the frame boss, it doesn't seem as it's "squashed".

Is 26.2mm the correct size for a 531 main tube?
I was expecting 27.2mm.
Mick F. Cornwall

pwa
Posts: 13694
Joined: 2 Oct 2011, 8:55pm

Re: seatpost sizes

Postby pwa » 18 Mar 2020, 10:56am

Mick F wrote:Dawes Lady Galaxy. 531 main tubes.

Stripping and checking it out, and taken the non-original seatpost out. Came out easily.

Looking at the post I see it's 26.2mm diameter, and looking at the frame boss, it doesn't seem as it's "squashed".

Is 26.2mm the correct size for a 531 main tube?
I was expecting 27.2mm.

If it is something like 531ST with thicker tube walls..

Brucey
Posts: 42324
Joined: 4 Jan 2012, 6:25pm

Re: seatpost sizes

Postby Brucey » 18 Mar 2020, 10:57am

If the tube walls are sized for touring purposes then the seat pin often ends up being 26.4mm (reamed) or 26.2mm (unreamed).

Thus some touring frames (even with slopey DB 531 transfers, but especially with 531ST markings (after a certain date)) will use about this seat pin size.

For the seat pin to be 27.2mm on a 1-1/8" OD tube requires that the wall be 0.7mm at the seat clamp. This isn't always deemed to be a good arrangement in a touring frame, especially if there are brazed joints midway along the length of the seat tube.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

User avatar
Mick F
Spambuster
Posts: 50718
Joined: 7 Jan 2007, 11:24am
Location: Tamar Valley, Cornwall

Re: seatpost sizes

Postby Mick F » 18 Mar 2020, 11:19am

Brucey wrote:If the tube walls are sized for touring purposes then the seat pin often ends up being 26.4mm (reamed) or 26.2mm (unreamed).

Thus some touring frames (even with slopey DB 531 transfers, but especially with 531ST markings (after a certain date)) will use about this seat pin size.
Thanks.
Looks like it'll be an un-reamed one then and post size is correct.

This is all that's left of the 531 sticker.
IMG_0083.jpg
Mick F. Cornwall

tatanab
Posts: 4344
Joined: 8 Feb 2007, 12:37pm

Re: seatpost sizes

Postby tatanab » 18 Mar 2020, 11:27am

That sticker is plain gauge 3 main tubes only. I had a couple of Claud Butler/Holdsworthy frames in that construction, 26.4 saddle pillar as I recall.

User avatar
Chris Jeggo
Posts: 196
Joined: 3 Jul 2010, 9:44am
Location: Woking

Re: seatpost sizes

Postby Chris Jeggo » 18 Mar 2020, 12:32pm

tatanab wrote:That sticker is plain gauge 3 main tubes only. ...

Agreed.
1-1/8" is a gnat's wotsit under 28.6mm and PG tubing is 1mm thick so I agree with
Brucey wrote:If the tube walls are sized for touring purposes then the seat pin often ends up being 26.4mm (reamed) or 26.2mm (unreamed). ...

bgnukem
Posts: 572
Joined: 20 Dec 2010, 5:21pm

Re: seatpost sizes

Postby bgnukem » 18 Mar 2020, 3:48pm

My '94 Dawes Mean Street has a galaxy frame in 531ST, with 1.0/0.7mm main tubes, and the seatpost is 27.0mm.