seatpost sizes

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Hudson1984
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Joined: 21 May 2012, 2:02pm

seatpost sizes

Post by Hudson1984 »

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
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Joined: 23 Jan 2020, 10:23am

Re: seatpost sizes

Post by thatsnotmyname »

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
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Joined: 4 Jan 2012, 6:25pm

Re: seatpost sizes

Post by Brucey »

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
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Hudson1984
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Joined: 21 May 2012, 2:02pm

Re: seatpost sizes

Post by Hudson1984 »

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
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Mick F
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Re: seatpost sizes

Post by Mick F »

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
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Mick F
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Re: seatpost sizes

Post by Mick F »

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
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Re: seatpost sizes

Post by pwa »

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
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Re: seatpost sizes

Post by Brucey »

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
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Mick F
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Re: seatpost sizes

Post by Mick F »

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
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Joined: 8 Feb 2007, 12:37pm

Re: seatpost sizes

Post by tatanab »

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.
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Chris Jeggo
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Location: Surrey

Re: seatpost sizes

Post by Chris Jeggo »

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
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Joined: 20 Dec 2010, 5:21pm

Re: seatpost sizes

Post by bgnukem »

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