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seat post length(7 posts)

seat post lengthmilt51
Mar 10, 2003 8:08 PM
I have a seat post that extends at least 8" into the seat tube.Can I cut some of the seat tube off ? How much should be inserted into the seat tube? Only 4" extend above the seat post clamp.
Thanks Milt
While it sounds as if you indeed have a too-long seatpost,bill
Mar 11, 2003 6:50 AM
I can't imagine that it makes sense to cut it off. I assume that you're worried about weight, but you'd save a very small amount of weight while possibly dinging the thing or otherwise compromising it's integrity.
Nah, please don't cut if off. You'll do it, and then you'll find one day that you need a post that's just that long.
Is it a MTB post? If it is, it may have a beefier clamp than you need, which is really where the weight is.
More thoughts about seatpost tube weightFez
Mar 11, 2003 8:10 AM
There was a thread on seatpost cutting couple of weeks ago.

The general consensus was that the weight was mostly in the clamp and not in the seatpost tubing.

And since frame tubes almost always weigh less than an equivalent length of seatpost tube, the weight savings of compact geometry frames must be very small, or nonexistent, if the compact frame requires a longer length seatpost.

Just something to think about - even if its a little off topic.

I would only cut a seatpost if it was so long that it hit the water bottle brazeon.
agreed, I cut one recentlylaffeaux
Mar 11, 2003 9:28 AM
I recently had to cut down a MTB seat post. The post was only available in 410mm length, which worked, but only allowed the seat to be dropped about 3/4" before hitting the water bottle braze on. I cut it down to 350mm for more adjustability.

If you use the right tools, this does not compromise the seatpost, so don't worry about that. It does render the "max insertion line" obsolete, which is a bit of a hassle. I weighed the 60mm of excess tube out of curiousity, and it was less than 15g (I forget the exact weight, but it was pretty minimal).
be careful of butted posts!StupidLight
Mar 11, 2003 6:57 PM
If your post is butted, I really wouldn't recommend cutting it -- if you cut into a thin section this could compromise the strength of the post. I've cut straight-gauge aluminum posts in the past, however with no problems.
not sure any seat posts are "butted"laffeaux
Mar 11, 2003 11:48 PM
The post I cut was a Thomson, which is butted front to back - thin on the sides and thick on the front and rear. I'm not sure it makes since to have a seat post that is butted with the larger diameter tube at the top and bottom - it would serve no pupose.
Ever heard of Easton, Dura-Ace, Bontrager, Kore, or Control Tech... ?StupidLight
Mar 12, 2003 7:40 AM
There are _tons_ of butted posts out there. If it's got an Easton sticker on it (like the dura-ace) it's likely butted.
The tubes don't change in diameter, merely in wall thickness.
Yes it's not always a simple question of thin in the middle, thick at the ends (the control tech, e.g. also has a cross-member down the middle), but butting and shaping the inside of the post has exactly the same purpose as butting frame tubes - saving weight! Even carbon posts which aren't "butted" in the metallurgic sense typically have some sort of reinforced area for clamping at the bottom of the post. This is why Easton carbon posts have a _max insertion_ mark -- they don't want you clamping on the thinner middle walls!