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Seatpost Fitting

Old 10-18-13, 12:43 AM
  #1  
PapaGanoosh
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Seatpost Fitting

I currently have a 26.6 seatpost on my road bike. I was wondering if using a 26.2 seatpost in the future will cause any problems in fitting? Will it be too small to fit in my frame leading to overtightening the lug in the back?
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Old 10-18-13, 01:11 AM
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If a 26.6 seatpost fits perfectly now with no play in it at all, then you need a 26.6 period. You should not play around with other size seat posts since all that will do is slowly weaken the seatpost and deform the seat post tightening ears. Your post should fit snugly with NO play.

A 26.2 post will be WAYYYY too small. You might barely get away with possibly using a 26.5 post but not sure if they even make such a thing.
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Old 10-18-13, 01:26 AM
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Originally Posted by PapaGanoosh View Post
I currently have a 26.6 seatpost on my road bike. I was wondering if using a 26.2 seatpost in the future will cause any problems in fitting?
Assuming the current one is a good fit - yes.

Originally Posted by PapaGanoosh View Post
Will it be too small to fit in my frame ?
Assuming the current one is a good fit - yes.

Originally Posted by PapaGanoosh View Post
...leading to overtightening the lug in the back?
Assuming the current one is a good fit - quite probably.

But you can always shim the 26.2 to something a lot closer to 26.6.
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Old 10-18-13, 04:45 AM
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I've been using a bronze seat post shim that is 3" long in my MTB since 1997. I'm tall and have a lot of seat post showing and for a period of several years I tipped the scales just a few ounces under 250 Lbs. I have experienced no issues using a shim.
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Old 10-18-13, 08:26 AM
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These threads drive me absolutely batty. Seatposts are available in basically every size ever used, and 99% of them can be had for dirt cheap.... Why not get the right size? It sounds to me like you already have the right size (if, in fact, 26.6 is the correct size for your frame)-- why not just keep that one in service?

If the current post is broken, why not just buy a danged 26.6mm post? I have like, three 26.6 mm posts in my basement, plus a few in some bikes. Common used 26.6 posts from the 80s are free or basically free when you find them. Brand new pipe-n-guts style seatposts are less than $5 (and an extra $2.50 for the guts). You might be tempted to save a few bucks by just using what's on hand, but consider this: a seatpost is a lot cheaper than a frame. Off-sized posts have killed a lot of frames over the years.
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Old 10-18-13, 09:21 AM
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More common sizes are 25.4 , or 1 inch, then you will find shims for all sorts of frame ID's
precision machined.. Wheels Mfg and QBP-PS both make seatpost sizing shims

less common 25.0, mm.. I have bought USE shims from the UK [through LBS]
they, the USE company, make seatposts just in 25 then in 27.2 , then again in larger than that
rather than all diameters in 0.2mm steps.

Kalloy makes seat posts like that they are very economical, and commonly available.

I bought a Thudbuster suspension seat post in 27.2, and a shim 27.2>31.4

to use in my frame with a 31.4 mm ID seat tube..

undersized seatposts, if used, damage frames , maybe irreversibly.

Last edited by fietsbob; 10-18-13 at 09:25 AM.
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Old 10-18-13, 09:58 AM
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Originally Posted by PapaGanoosh View Post
I currently have a 26.6 seatpost on my road bike. I was wondering if using a 26.2 seatpost in the future will cause any problems in fitting? Will it be too small to fit in my frame leading to overtightening the lug in the back?
Question.

If the 26.6 post fits and works, why would you even consider another? It's like saying I've worn size 9 shoes all my life, but I'm thinking of trying some size 7.

Post fit is very critical, and has to be a running fit inside the tube. Otherwise, even if you can clamp it at the top, it's rock and move around below, creaking and putting undue stress on the seat tube just below the clamp
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Old 10-18-13, 11:01 AM
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Originally Posted by FBinNY View Post
Question.


If the 26.6 post fits and works, why would you even consider another? It's like saying I've worn size 9 shoes all my life, but I'm thinking of trying some size 7.


Post fit is very critical, and has to be a running fit inside the tube. Otherwise, even if you can clamp it at the top, it's rock and move around below, creaking and putting undue stress on the seat tube just below the clamp

I wanted to install a fluted seat post and had a 26.2 lying around. Was wondering if I should get another one.
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Old 10-18-13, 11:08 AM
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Math: 26.6mm - 26.2mm = 0.4mm '/, 2 = 0.2mm, you need an 0.2mm thick shim to make up the difference..

what makes the fluted seat post so special ?

its a look that has been done in cheap as well as expensive seatposts ..
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Old 10-18-13, 12:22 PM
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I had a person that came in to my shop last night asking fo a seat pole. You mean a seat post? "Yeah, seat pole." What size? "A long one." No, no, a seat post, what diameter, how thick? "Yeah, a long one, for a crusier. A pole." show him the parts binwith seat poles, eh posts. He grabes a long one, "Yeah, that's for a cruiser, How much?" 2 bucks. Pays and leaves happy.

I know it doen't help the op, but since we are talking about poles...
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Old 10-18-13, 04:36 PM
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Many "crusier poles" are going to be 13/16", 7/8", or 1".... so, maybe he got lucky?
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Old 10-18-13, 09:29 PM
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Originally Posted by leob1 View Post
I had a person that came in to my shop last night asking fo a seat pole. You mean a seat post? "Yeah, seat pole." What size? "A long one." No, no, a seat post, what diameter, how thick? "Yeah, a long one, for a crusier. A pole." show him the parts binwith seat poles, eh posts. He grabes a long one, "Yeah, that's for a cruiser, How much?" 2 bucks. Pays and leaves happy.

I know it doen't help the op, but since we are talking about poles...
Ugh, I HATE ignorant customers like that. Its one thing if the customer is ignorant but willing to learn how to fix the bike or learn the proper terms but people like your customer drive me nuts with their thickheadedness.
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