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I've got an american classic seatpost. I bought it used, and wasn't sure how to properly adjust it initially. I found the bolt on the bottom clamps the seat down. The bolt on the rear underside adjusts the saddle angle.

But the bolt on the front was a mystery. I took the post out and looked at it and you can see that the bolt on the front of the post connects to this rod inside the post.

The rod has a fixed end which is inserted up in to the seat tube, and the bottom of the rod is threaded and has a small alloy knob on the bottom. It appears to flare at the bottom and has a slit in the bottom of the seat tub where this knob rests. I have no idea how you would tighten this from outsidem But it looks almost like you could tighten it like a stem for a treaded headset.

What is this for and why did they include this on the seatpost?

Seatpost Seatpost

Close up of bottom of Seatpost with Rod (You can't see it, but there is a slit in the font of the seatpost)

Close up of bottom of Seatpost with Rod

Rod Removed from Seatpost Rod Removed from Seatpost

Bolt on front of Seatpost Bolt on front of Seatpost

  • One interesting thing. I can't figure any way to adjust the nut at the end of the rod from the top. I guess you could remove the little rubber plug from under the seat clamp and get some weird tool to turn the skewer like thing inside the seatpost. I'm guessing it would require some specialized tool though. – Benzo Feb 21 '15 at 22:18
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    I would assume that the intent is that you pull the assembly snug, to slightly expand the bottom of the post, so it snugly fits into the seat tube. This eliminates wobble and allows the post to be safely used with a slightly higher extension. Should probably not be tightened so much as to prevent seatpost adjustment via the top clamp.. – Daniel R Hicks Feb 22 '15 at 13:01
  • How would you tighten it? Before inserting in to the frame or after? – Benzo Feb 23 '15 at 12:42
  • I guess I'd try inserting it into the frame, then tightening to "snug" but such that the post can still move up and down. – Daniel R Hicks Feb 23 '15 at 12:47
  • Ok. I'm thinking that the bolt on the front of the post might provide some small amount of additional tension. So I would have to tighten the nut at the bottom of the post before inserting so that I can barely get the post in the seattube and then try to add some tension via the bolt on the front of the seatpost, which appears to enter the top of the rod at a 45 degree angle, so tightening this would pull it to one side and up a bit, creating some additional tension. – Benzo Feb 23 '15 at 15:31
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I had a Peugeot bike once where the seatpost didn't have the usual clamp but a similar system to hold it in the seat-tube. The system was not very practical because if you wanted to adjust the saddle height you could only do so if the saddle was removed. The bolt was tightened from the top of the seatpost. There was a second draw-back: the seat-tube being rather thin walled you had to be be careful when tightening or you could ruin the tube. Your bicycle has a normal clamp so I would remove this long bolt with the cone and save hassle and weight.

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