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Tripolar on most days
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440 Posts
Discussion Starter #1
seatpost sizes are so close does it matter if you use the wrong one. A 26.8mm is 1.05512'' and a 27.2 is 1.07087'' that is only .01567'' differance. Is it possiable to use a 27.2 instead of a 26.8. I know that my bike is one of the two but I have read different spec's on the bike. It is a Bianchi D.I.S.S. and some of the spec's say its 26.8 and some say it is 27.2. I know the new Bianchi SASS spec's out a 27.2. If someone can tell me what it is or if I could use either one and what could happen if I use the wrong one.

Thanks
 

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Derailleurless
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9,122 Posts
Nope, gotta stick with what you've been given. You can fudge 0.1mm here and there, but that's about the extent of it. Stretch it to 0.2mm and you'll feel the difference. The 0.4mm difference you're talking about is pretty significant.

Too large and you'll have to "screw it in". To small and it'll slip on ya. Do either to an aluminum frame and you're asking for damage at the clamp area from the extra wiggling and bending.
 

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Old man on a bike
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12,383 Posts
I guess your motto means something here but

not sure exactly what. Have you thought of measuring it? I certainly wouldn't recommend jamming a 27.2 post in there, you would probably wreck the seat tube. A 26.8 post in a 27.2 seat tube would work with a shim perhaps, but otherwise you surely would wage a losing battle with slippage. Measuring is easier. Some posts have the diameter etched in somewhere toward the bottom of the post...
 

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Tripolar on most days
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440 Posts
Discussion Starter #4
Thanks guy's

I just dug out my digital calipers and it's a 26.8
 
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