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27.2mm seatpost 1mm too wide

Old 05-18-24, 02:09 AM
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27.2mm seatpost 1mm too wide

In 2020, I bought a SATORI Solo Bike Bicycle Suspension Seatpost 27.2x350mm for my 2010 Fuji Absolute 2.0. It replaced the orig. w/o any issues.
For my 1993 Gary Fisher advance mtb frame, I purch'd the same Satori seatpost. And it turns out to be about 1mm too wide for the GF seat tube. Ditto 1mm too wide for my recent Miyata 512. So I'm suspecting some sort of new standardization issue -- "how manufs measure 27.2mm" issue. Has "27.2mm" changed between 1993 and 2010?
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Old 05-18-24, 03:05 AM
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Measure the OD of both seat posts with a caliper (at several points, to confirm that the diameter is consistent). Do they differ by 1 mm?
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Old 05-18-24, 03:06 AM
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Have you measured the stock seatpost on either bike?
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Old 05-18-24, 04:17 AM
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My '94 Bruce Gordon Rock & Road takes a 26.8mm seatpost. Maybe your '93 GF does too?
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Old 05-18-24, 04:34 AM
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Originally Posted by elcyc
In 2020, I bought a SATORI Solo Bike Bicycle Suspension Seatpost 27.2x350mm for my 2010 Fuji Absolute 2.0. It replaced the orig. w/o any issues.
For my 1993 Gary Fisher advance mtb frame, I purch'd the same Satori seatpost. And it turns out to be about 1mm too wide for the GF seat tube. Ditto 1mm too wide for my recent Miyata 512. So I'm suspecting some sort of new standardization issue -- "how manufs measure 27.2mm" issue. Has "27.2mm" changed between 1993 and 2010?
Specs show a 26.4 seatpost for the Advance
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Old 05-18-24, 04:41 AM
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Likewise, it is very unlikely your Miyata used a a 27.2 mm post. Sheldon Brown’s data base does not list a 512, but almost all the Miyatas on it are 26.8.

Measure the seat tube internal dimension (in a few directions to ensure roundness) before you buy.

You can ream a steel seat tube, but it’d be better in most situations to just buy the correct size post.
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Old 05-18-24, 05:26 AM
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https://www.harborfreight.com/home/h...per-63586.html
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Old 05-18-24, 05:27 AM
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Ooops....
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Old 05-18-24, 06:20 AM
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Median or mean , not max

Originally Posted by DorkDisk
Specs show a 26.4 seatpost for the Advance
Saw that before. Because of the of clamp, the diameter spec is likely an averaged value, not max.
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Old 05-18-24, 06:37 AM
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Originally Posted by elcyc
Saw that before. Because of the of clamp, the diameter spec is likely an averaged value, not max.
What the heck does that mean? It's not complicated. The bike takes a 26.4 seatpost, not a 27.2.
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Old 05-18-24, 06:40 AM
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Originally Posted by elcyc
Saw that before. Because of the clamp, the diameter spec is likely an averaged value, not max.
The point: given the information that you've posted in this thread, you're trying to jam your seat post into a frame that wasn't meant to take that diameter.

FYI, many suspension seat posts are designed in a small diameter and supplied with shims for various seat tube dimensions. If you want to use a suspension seat post with the bike, get one of those.
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Old 05-18-24, 06:54 AM
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There wasn't any standard BITD. It was more to do with type of tubing and where the bike was manufactured. Does the Miyata have Miyata's triple butted splined tubing? I think those took 26.8. I have an 85 912 and a 90 Team Miyata. They both take 26.8. I think 27.2 was mostly a Columbus tubing thing, but don't quote me on that.
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Old 05-18-24, 07:09 AM
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Originally Posted by elcyc
Saw that before. Because of the of clamp, the diameter spec is likely an averaged value, not max.
This is incorrect. A seatpost needs to be the proper fit to the seat tube of the frame. Try clamping a seatpost that’s even 0.2mm under spec and you’ll see it doesn’t stay in place.
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Old 05-18-24, 07:15 AM
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Using my trusty analog caliper, I measured everything prior to posting the OP.
Did it again. If you want photos, lemme know.
For both the Miyata and GF, the orig stock seatpost has a OD of 27.17.
The Satori is 27.22.
One reason the Satori may not fit is that has quite the thick paint job. Also, it has a matte surface; it is not the std "silver smooth" that one normally sees.
On Amazon the most common size seems to be 27.2. That's where I got it from.
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Old 05-18-24, 07:20 AM
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Originally Posted by elcyc
Using my trusty analog caliper, I measured everything prior to posting the OP.
Did it again. If you want photos, lemme know.
For both the Miyata and GF, the orig stock seatpost has a OD of 27.17.
The Satori is 27.22.
One reason the Satori may not fit is that has quite the thick paint job. Also, it has a matte surface; it is not the std "silver smooth" that one normally sees.
On Amazon the most common size seems to be 27.2. That's where I got it from.
Just to clarify: you're still talking about trying to insert a seat post marked 27.2 into the seat tube of a bike whose spec sheet calls for a 26.4 post, correct?
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Old 05-18-24, 07:21 AM
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Originally Posted by Trakhak
FYI, many suspension seat posts are designed in a small diameter and supplied with shims for various seat tube dimensions. If you want to use a suspension seat post with the bike, get one of those.
In 2004, for my GF, I did get --and still use-- a Performance Bicycle suspension post. It came with that shim which makes the OD 27.2mm.
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Old 05-18-24, 09:33 AM
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You can continue twisting in the wind or you can buy the correct size seatpost. Your choice.
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Old 05-18-24, 10:05 AM
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Originally Posted by elcyc
Saw that before. Because of the of clamp, the diameter spec is likely an averaged value, not max.
Originally Posted by shelbyfv
What the heck does that mean? It's not complicated. The bike takes a 26.4 seatpost, not a 27.2.
Average diameter is important when you're trying to fit a square peg in a round hole ...
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Old 05-18-24, 10:40 AM
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Originally Posted by elcyc
Using my trusty analog caliper, I measured everything prior to posting the OP.
Did it again. If you want photos, lemme know.
For both the Miyata and GF, the orig stock seatpost has a OD of 27.17.
The Satori is 27.22.
One reason the Satori may not fit is that has quite the thick paint job. Also, it has a matte surface; it is not the std "silver smooth" that one normally sees.
On Amazon the most common size seems to be 27.2. That's where I got it from.
So it is extremely unlikely that the Satori is painted in fact is is pretty rare that seatposts are painted except on custom bikes usually the are anodized and the anodization is not really adding thickness and even if so they accommodate for that and the silver generally is also anodization and not just raw aluminum.

Given the information people have given it seems like you have attempted to put the incorrect sized seatpost into the frame.

Amazon has absolutely nothing to do with this topic. Just because they sell more of a certain size of something doesn't mean your bike is that size. It clearly is not. My 80s era Cilo frame was 26.8 and the Phil Wood frame that replaced it is 27.0 and you can find all sorts of different sizes out there sometimes still to this day. The thing with standards is there is always a new one and it doesn't solve the problems it just adds to the standards.

I am unsure how you measured but if you are measuring anything but the current fitting seatpost at different points along it with a proper set of calipers you are probably doing it wrong. Either that or you want to measure the ID of the seat tube with the clamp off or loose and again measure several times around it and confirm. You must also know how to use the calipers and measure properly. I know plenty of people who don't really know how to use calipers properly so it is not an attack on anyone it is a skill people haven't been taught or haven't learned on their own.

In terms of a suspension post if it just goes up and down, skip it, it will be doing bad for your knees. Look for something like the Kinekt which is going to be tunable, way more comfortable and goes down but also back to keep your knees in a good position. They don't make it for smaller than 27.2 but these days for new bikes generally you will find mostly 27.2, 30.6 and 31.8 as the common sizes it doesn't go all across the board mind you.
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Old 05-18-24, 11:40 AM
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Typical of BF, not one useful reply (that was not my own). NOT ONE!

Just a bunch of small talk, non sequiturs and platitudes.
This fella gave up on BF, too:
Seatpost Won't Fit

Can any of you responders even pump a tire?

Have a flowery day!










BTW: The Miyata specs note: SR CRE-110 OD: 26.8x230L
REFS:
https://forum.cyclinguk.org/viewtopic.php?t=73318
https://www.peterverdone.com/27-2-to...-modification/
https://weightweenies.starbike.com/f...c.php?t=162455

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Old 05-18-24, 11:48 AM
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Originally Posted by Trakhak
Just to clarify: you're still talking about trying to insert a seat post marked 27.2 into the seat tube of a bike whose spec sheet calls for a 26.4 post, correct?
See above. Just need a yes or no answer. If the answer is no, I'll bow out.
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Old 05-18-24, 11:53 AM
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Originally Posted by elcyc
For both the Miyata and GF, the orig stock seatpost has a OD of 27.17.
The Satori is 27.22.
OP: " The suspension seat post doesn't fit. I measured the stock seatpost and it is the same diameter as the suspension seat post."

This is what I call a logical disconnect ..... competing claims which are mutually exclusive. If the difference is really .05 mm, a little sandpaper or even a little lube (which you should be using anyway) should be sufficient. I have in the past (on steel frames) opened up the split seat tube a little (prying sort of gently with a flat-blade screwdriver) to get a painted seatpost into a seat tube ... but only when I knew it was the right size.

Given that there is dealer documentation that the Gary Fisher frame has a smaller seat tube ...

Also, I assume you easily inserted the Miyata seat tube in the Gary Fisher frame, right? Just to check? And it slid right in because the two (seatposts from the Fisher and the Miyata) are the same size, right?

When someone tells me things which are logically impossible, I look for clarification.
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Old 05-18-24, 12:18 PM
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Originally Posted by elcyc
Saw that before. Because of the of clamp, the diameter spec is likely an averaged value, not max.
The important number is the inside diameter of the seat tube, it would seem it’s designed to accept a 26.4 seatpost. Maybe a blowtorch and a sledgehammer will get the bigger seatpost installed.

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Old 05-18-24, 12:51 PM
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Originally Posted by elcyc
Using my trusty analog caliper, I measured everything prior to posting the OP.
From your pictures, your caliper is damaged such that you need to measure the opening with a separate ruler. I would not call that at all trustworthy.
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Old 05-18-24, 01:07 PM
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Originally Posted by Aubergine
From your pictures, your caliper is damaged such that you need to measure the opening with a separate ruler. I would not call that at all trustworthy.
It's not damaged -- you read it at the scribed marks.
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