Seat Post size 27.2 vs 27.4
01-06-15, 06:31 PM
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Seat Post size 27.2 vs 27.4
Has anyone tried to tighten a 27.2 seat post in a frame designed for 27.4. Will it tighten with shims? Is there any real noticeable difference? thanks
01-06-15, 06:40 PM
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With the proper shim it will work. Without the proper shim you will probably damage the clamp area of the seat tube with an undersize seatpost.
01-06-15, 09:14 PM
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You have 3 options:
Get a 27.4 seat post.
Use a beer can to shim down to 27.2.
Buy a premade shim for a 25.4 post.
Get a 27.4 seat post.
Use a beer can to shim down to 27.2.
Buy a premade shim for a 25.4 post.
01-06-15, 09:18 PM
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...the difference when you shim a smaller seatpost is that instead of having a firm support from the slip fit for the length of your post, you only get that for the length of the shim.You may or may not notice it,but it is for this reason that I try to avoid it. I suppose if you're using either a short post or a longer shim, this is not so much a problem.
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01-06-15, 10:55 PM
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...the difference when you shim a smaller seatpost is that instead of having a firm support from the slip fit for the length of your post, you only get that for the length of the shim.You may or may not notice it,but it is for this reason that I try to avoid it. I suppose if you're using either a short post or a longer shim, this is not so much a problem.
Asssuming you have the right amount of shim to bring the post to diameter at the clamp, there's still the issue of support against rocking inside the frame. It takes at least 1-1/2 diameters of the post to give it solid support against rocking, and roughly 3" of good support to absolutely ensure it won't creak.
So you can get by with a DIY shim, and if it doesn't creak count yourself lucky. Otherwise but a commercial shim 3" long, or improvise one of that that length.
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01-07-15, 06:06 AM
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If you improvise a shim make sure to leave a lip or something at the top so it is less likely to fall down into the tube when inserting/removing it and you won't need three hands.
01-07-15, 09:22 AM
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Common machine made shims (with top lip-flanges come in IDs of 1" And 27.2
Though those in&outside dimensions are not offered on this List. Ie, shim of 0.1mm thickness
Problem Solvers
Triple check that it is actually a 27.4 ID seat tube , rather Odd, someone over did the reaming in the factory?
Though those in&outside dimensions are not offered on this List. Ie, shim of 0.1mm thickness
Problem Solvers
Triple check that it is actually a 27.4 ID seat tube , rather Odd, someone over did the reaming in the factory?
Last edited by fietsbob; 01-07-15 at 09:25 AM.
01-07-15, 12:11 PM
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01-12-15, 01:30 AM
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Common machine made shims (with top lip-flanges come in IDs of 1" And 27.2
Though those in&outside dimensions are not offered on this List. Ie, shim of 0.1mm thickness
Problem Solvers
Triple check that it is actually a 27.4 ID seat tube , rather Odd, someone over did the reaming in the factory?
Though those in&outside dimensions are not offered on this List. Ie, shim of 0.1mm thickness
Problem Solvers
Triple check that it is actually a 27.4 ID seat tube , rather Odd, someone over did the reaming in the factory?
Doesn't work so well when I need to readjust the post though, like when I swapped saddles. The best solution would be to buy the right size post and be done with it.
