# Shortening a seatpost



## RayGun (Dec 8, 2006)

Is there any problem with cutting a 330mm seatpost down to 240mm?

I saw that a Thomson Masterpiece was available for a good price but it it's at the longer length.

Has anyone done this?


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## mwestray (Jan 4, 2008)

I have cut seatposts to shorten; a simple job with a hacksaw and a file and sandpaper to remove burrs. Seems a shame to cut a beautiful Masterpiece post, but no one ever sees the bottom end.


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## MR_GRUMPY (Aug 21, 2002)

After the cut, it might be wise to bevel the end a little, with a file.


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## 2cflyr (Apr 9, 2002)

MR_GRUMPY said:


> After the cut, it might be wise to bevel the end a little, with a file.


yes- use a file, not sandpaper. MUCH more better. 

I'd guess that you could treat it like an aluminum/steel fork steerer and use one of these fancy things if you were truly picky.


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## andulong (Nov 23, 2006)

Sure, just make sure you cut it off the bottom.


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## danl1 (Jul 23, 2005)

Before you cut, measure from the bottom to the minimum insertion line. Figure where you want the new minimum line to be (nearish the seatpost collar at your desired height) and measure back down to your cut line. Do the mechanicals as described by others, and done.


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## BikeGeek (Mar 19, 2005)

Make sure the cut down post extends at least a little below the bottom of the top tube at your desired setting so you dont stress the seat tube excessively.


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## DieselDan (Sep 14, 2002)

Use a tube cutter.


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## Mel Erickson (Feb 3, 2004)

Cut it with whatever you want. Hack saw, tube cutter, torch, whatever. Just make sure you have the same amount of post inserted as the minimum on the original post. Really doesn't matter whether you bevel the end or not or whether there are burrs or not as long as it inserts and slides in the seat tube properly. I've cut several over the years, no problemo. Of course, if there's a burr that causes it to catch in the seat tube it has to be removed but otherwise, no one will ever see it and how it looks will never make a difference.


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## Squidward (Dec 18, 2005)

DieselDan said:


> Use a tube cutter.


This won't work very well. I had an old junk seatpost laying around that I was messing with one day and decided to cut off the scarred up end so that I could use the good tube for some project. I used a tube cutter to score the aluminum then decided to cut it through. First of all, it would have been a lot less work using a hacksaw to cut it. Second, the tube cutter works by displacing the material, basically pushing it aside. When the roller wheels on the other side roll over the displaced aluminum, it flattens it. What happens is that you will end up with a raised but of aluminum at the cut that you will need to grind down with a file or something. Not only that but when the tube finally breaks it leaves a really jagged edge on both sides that requires a lot of attention with a file in order to prevent you cutting your hands open on them. Use a hacksaw instead.


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## nismosr (Jun 27, 2007)

2cflyr said:


> yes- use a file, not sandpaper. MUCH more better.
> 
> I'd guess that you could treat it like an aluminum/steel fork steerer and use one of these fancy things if you were truly picky.



Where can I get this kind a tool and what do you call them ?


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## tron (Jul 18, 2004)

Tube cutters are great. I picked one up at the hardware store for about 4 dollars. If you get a bike specific one it will cost 3x as much for the same tool


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## Paul1PA (Sep 16, 2006)

I recently saw a Masterpiece at the LBS. Like the Thomson Elite, this post had the elliptical I.D. with a thicker wall on front & back. In addition, the shop manager also thought the internal profile varied along the length of the Masterpiece (sort of like a butted frame tube) to shave off more weight.

Assuming this is true, I would proceed with caution. By removing ~3.5" from a post designed for MTBs, you could then expose a thinner walled section to a clamping or shear force it wasn't designed to handle. I'll admit, an unlikely scenario but this is an extremely light weight component engineered to the absolute limit. Best to be safe and pose the question directly to Thomson. 

Paul


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## Mel Erickson (Feb 3, 2004)

Yes, a Thomson post is elliptical on the inside to save weight and still keep it strong. Tubing cutters would have more of a problem cutting them than a hack saw but they would still work. The tubing is consistent top to bottom on the inside so you can cut a Thomson with no problem.


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## cww180 (Aug 31, 2008)

What is the minimum insertion depth on the Thompson's? I was looking to buy one off of ebay but its already cut and I want to know how much post I will have left. What is considered the normal minimum insertion depth?


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## cyclust (Sep 8, 2004)

The thomson masterpiece is such a light post that cutting it shorter will save very little weight. I'd leave it alone, unless it is too long to get it in the frame. If you cut it, you may limit it's use in the future in a different application. A 4" section of that post will weigh maybe an ounce.


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## mwestray (Jan 4, 2008)

Take a look at the specs on Thomson's website: http://www.lhthomson.com/sp_tech_support.htm

For the Elite post, the minimum insertion varies from 63.5mm to 100mm depending on diameter and usable length (length from min insertion to top of the post). For the Masterpiece, the minimum insertion varies from 63.5mm to 87mm.


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## Andrea138 (Mar 10, 2008)

nismosr said:


> Where can I get this kind a tool and what do you call them ?


That's a saw guide. They're most often used when cutting a steertube:


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## capt_phun (Jun 14, 2004)

Plus if you cut it short & try to resell it later you are seriously devaluing the masterpiece.


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## bwhite_4 (Aug 29, 2006)

How much do you want to cut off the post and how many grams are you expecting to save?


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## Stogaguy (Feb 11, 2006)

*+1 - Tube cutter hassle*

I agree that the tube cutter sounds like a better idea than it really is. It will make a perfectly straight "cut", but it will (as described) require a lot of finishing work to properly bevel the end. I know this from experience cutting an old design American Classic post.

IMHO the best solution is saw guide and a hacksaw with a new blade followed by a very fine file for clean-up and final beveling.


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## CleavesF (Dec 31, 2007)

capt_phun said:


> Plus if you cut it short & try to resell it later you are seriously devaluing the masterpiece.


+1, there's no point of "tuning" any parts on your bike unless you are sure it's going to be a "terminal part".


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