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PostPosted: Sat Jul 14, 2018 10:09 am 
Dirt Disciple

Joined: Sun Jul 12, 2015 4:23 pm
Posts: 18
I bought a mid 90s Menet (Martelly) road bike earlier this year which has Columbus Neuron tubing all round. I have only just got round to changing the saddle and found two issues:

Firstly that one half of the micro adjust saddle rail clamp on top of the (Easton) seatpost was cracked, something I had never noticed. Clearly it needs to be replaced as I assume it is not possible to buy individual components?

Secondly, when removing the seatpost it was very tight. It is clearly the wrong diameter for the seat tube. I did get the seat post out OK and the tube was quite clean, no rust etc which seems to confirm it's down to non-compatible seatpost diameter. I have measured the diameter of the seatpost with digital calipers and it is 27.25 mm. The internal diameter of the tube is probably 27.0 but on the calipers it was coming up at 27.03. However, I understand that Neuron tubing is slightly eliptical so I have tried to find specs of Neuron tubing online but have drawn a blank. The external diameter of the seat tube is 29.15mm.

Assuming that the internal diameter of the seat tube is 27.0mm am I right in thinking I need a seat post that is 0.2 smaller than the internal diameter of the seat tube? i.e. 26.8mm?

Finally, the seat post is 200mm long plus the rail clamp on top. I have noticed that most seatposts seem to be 400mm long.....is it possible to buy a 200mm post?


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PostPosted: Sat Jul 14, 2018 1:04 pm 
King of the Skip Monkeys
King of the Skip Monkeys

Joined: Wed Nov 07, 2007 4:34 pm
Posts: 29010
Try a different 27.0, if it slides in and out without to much effort, thats your post.

As for length, most get chopped down to suit but there are also plenty of 300mm posts too.


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PostPosted: Sat Jul 14, 2018 1:24 pm 
Dirt Disciple

Joined: Sun Jul 12, 2015 4:23 pm
Posts: 18
legrandefromage wrote:
Try a different 27.0, if it slides in and out without to much effort, thats your post.

As for length, most get chopped down to suit but there are also plenty of 300mm posts too.



I'm sure I can get hold of a 27.0 to try. I'm sure you're right because the 27.25 will come in and out without too much of a fight now that it is greased properly.

I did wonder about chopping a 400mm post down. Is this something I can do or does the cut end need to be specially finished? I have various sized files so can cut down and file it.

I reckon a 300mm post would be fine as the cut off point is the brazings on the seat tube for a bottle cage and I can probably get away with 325mm above the bbrazings.

Great advice, thank you! :)


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PostPosted: Sat Jul 14, 2018 1:26 pm 
King of the Skip Monkeys
King of the Skip Monkeys

Joined: Wed Nov 07, 2007 4:34 pm
Posts: 29010
The bike shop I worked at used to regularly chop posts down so just measure where the safety line is and mark the post accordingly.

Wear a mask if its a carbon post. If you're really good you can chamfer the edges so it looks nice on alumnium posts.


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PostPosted: Sat Jul 14, 2018 1:35 pm 
Dirt Disciple

Joined: Sun Jul 12, 2015 4:23 pm
Posts: 18
legrandefromage wrote:
The bike shop I worked at used to regularly chop posts down so just measure where the safety line is and mark the post accordingly.

Wear a mask if its a carbon post. If you're really good you can chamfer the edges so it looks nice on alumnium posts.


Perfect, I will have a go if I need to go with a 400mm post. I'm sure I can chamfer the edges no trouble and I guess that will help the post down into the tube too.

Thanks again..........


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PostPosted: Sat Jul 14, 2018 1:40 pm 
King of the Skip Monkeys
King of the Skip Monkeys

Joined: Wed Nov 07, 2007 4:34 pm
Posts: 29010
I can only go by my own experience so give it a mo in case some else has more info.


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PostPosted: Sat Jul 14, 2018 1:45 pm 
Dirt Disciple

Joined: Sun Jul 12, 2015 4:23 pm
Posts: 18
legrandefromage wrote:
I can only go by my own experience so give it a mo in case some else has more info.


I won't do anything until next week but everything you said makes perfect sense and it seems that I have more options in a 27.0 post than a 26.8, certainly if I want to hang out for a sub 300mm post.


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