31.6 seat post in a 31.9 ID seat tube?
08-29-19, 09:20 AM
#1
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Thread Starter
31.6 seat post in a 31.9 ID seat tube?
Just making sure I'm good here.
This will work right?
Thanks in advance.
Brandon
This will work right?
Thanks in advance.
Brandon
08-29-19, 01:57 PM
#2
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As far as I'm concerned, it ain't a sin to shim.
08-29-19, 02:53 PM
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What seat tube has a 31.9 ID? A 31.6 is not going to work well in a 31.9 ID tube. I'd search for the elusive 31.8 seat post or use a soda can shim.
08-29-19, 08:06 PM
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AS this is a frame building forum (and not a bike assembly forum) I'll assume that the ST ID is prior to making the frame. With this I'll say that the ID of importance is after the frame has been built.
It's well known that many thousands of 27.2 posts are in seat tubes that measured 27.4 ID before the flame hit the frame.
Now I'll put on my bike assembly hat- Have you measured the ID? If so how? Have you tried a test fit or tighten of any seat post yet? If so results? Andy
It's well known that many thousands of 27.2 posts are in seat tubes that measured 27.4 ID before the flame hit the frame.
Now I'll put on my bike assembly hat- Have you measured the ID? If so how? Have you tried a test fit or tighten of any seat post yet? If so results? Andy
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AndrewRStewart
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08-30-19, 05:51 AM
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my understanding is that you need some clearance for a good seat post fit. Typical .6 wall 28.6 OD tubing = 27.4 ID is the proper size for a 27.2 post. But .3 difference might be pushing things.
08-30-19, 10:33 AM
#6
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Thread Starter
Well crap. I believe this is the ST that we used in my frame school: https://www.bikefabsupply.com/seat-t...be-969-rid-272. It says 31.7, but I keep measuring 31.9 with the calipers. I didn't keep the shim that came with it since I wanted to use this post: https://www.merlincycles.com/deda-su...ost-71123.html, and since I didn't think the shim would look right with the work that was done on the top of the ST.
It seems that I'll need to keep searching then. I can't seem to find the correct sized shims for the above.
Thanks all.
Brandon
It seems that I'll need to keep searching then. I can't seem to find the correct sized shims for the above.
Thanks all.
Brandon
08-30-19, 10:56 AM
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That tube has a 31.7 OD on one end and 32.3 OD on the other end. Neither end will fit a 31.6 post. The tube has an ID of 29.9 on one end and 30.5 on the other end.
There are a few 29.8 seatposts that will work in the 31.7 end, if that is the way you built the frame.
There are a few 29.8 seatposts that will work in the 31.7 end, if that is the way you built the frame.
08-30-19, 11:48 AM
#9
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Thread Starter
Thanks all. I'll have to get that shim I guess. Because of the custom work I did on the ST, the shim will have to be modified to look right. Looks like I'm stuck on this. Pic shows the top of the ST.
