# Cut down the seatpost?



## roadrap (Feb 17, 2007)

OK, I've wondered this for a while but never seen any post on this...does it hurt anything if I cut down my aluminum seat post? There is about as much of it hidden as there is exposed, so I'm thinking why not cut a few inches off. May not be that much grams, but why have it, if it can be trimmed? 

Also, assuming I carry a couple of extra pounds of water, cages, tube, tools, etc is there any specific advantage to where that weight is placed - for example, water behind the seat, on the frame, or in a camelbak. Repair stuff under the seat, or in a camelbak.  Or is two pounds, two pounds no matter where it is? I don't race but I do centuries and some mountains, and always trying to improve performance. Bike is 18 pounds base.


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## ctracer01 (Jan 5, 2006)

*hacksaw it up....*



roadrap said:


> OK, I've wondered this for a while but never seen any post on this...does it hurt anything if I cut down my aluminum seat post? There is about as much of it hidden as there is exposed, so I'm thinking why not cut a few inches off. May not be that much grams, but why have it, if it can be trimmed?
> 
> Also, assuming I carry a couple of extra pounds of water, cages, tube, tools, etc is there any specific advantage to where that weight is placed - for example, water behind the seat, on the frame, or in a camelbak. Repair stuff under the seat, or in a camelbak. Or is two pounds, two pounds no matter where it is? I don't race but I do centuries and some mountains, and always trying to improve performance. Bike is 18 pounds base.



your seatpost needs to be below the bottom of the top tube weld. other than that, cut away. just know you're cutting away the resale value it may possess.

as for the weight, it depends on what you're looking for, and your riding style. if you're looking for a lighter feel of the bike, you want the weight as close to the ground as possible. This is so the weight will not be accelerating/deccelerating as much as it would be if it were higher up on your bike, and thus on a higher arc of motion.

if you're looking for aerodynamics, then it's worst to put your bottles behind your seat, better to have a camelback, and best to have them on your frame (tests show a regular bike is more aerodynamic with bottles on, with the best result coming from one bottle on the seat tube).

if you've got a camelback, and don't mind the weight, it's probably best of both worlds to throw tools and such in there, as long as they're not bulging out like crazy.

are you really gonna feel this difference? probably not. :idea: 

is it fun to tinker? hell yea. :thumbsup: :thumbsup: :thumbsup: :thumbsup:


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## Squidward (Dec 18, 2005)

I just weighed a 4.75" section of 27.2mm seatpost that I had cut off a cheapo seatpost. That piece of aluminum tubing has a wall thickness of about 4mm or 3/16". It weighs a whopping 75 grams (about 2.9 ounces).. Keep in mind that a higher-end aluminum seatpost uses a higher grade of aluminum and has wall thicknesses that are thinner than this Kalloy POS that I chopped up, meaning that lopping 5" off your American Classic or other high-quality aluminum seatpost will save you an ounce or two.


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## JCavilia (Sep 12, 2005)

*I'd be a little more careful than that*

Your post has a minimum-insertion mark. There's probably a little safety margin in that, but I think the mark puts the end of the post well below the bottom of the top-tube weld. I'd measure the distance from the bottom of the (unmodified) post to the mark, and make sure that I still had that much inserted after the modification. In other words, I'd only cut off the post if, and to the extent that, my proper fitting had the post lower than the maximum extension. I'd add a new mimimum insertion mark, too. 

A shorter insertion increases the leverage exerted by the post in the frame, and increases the chances of creaking, frame damage, or failure. The seat post and its junction with the frame (like crank and handlebar) is one of those "critical failure" points -- 'cause you hurt a lot if it breaks suddenly.


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## roadrap (Feb 17, 2007)

*Thanks, good info*

Thanks folks, this is good info. Kind of what I was thinking but it helps to get the feedback. Looks like I can safely cut off a few ounces if I decide to do it. ctracer01, you are right, may not notice much if at all, but the tinkering is fun and is a great excuse to take a 50 miler to "test things out". I've learned from years of backpacking that the way to get a pack from 40 pounds to 20 pounds is a few ounces at a time. Although with bikes there is a balance point where getting any lighter just costs more and more.


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