31.8 Seat tube diameter, what size seatpost?
04-06-11, 11:21 AM
#1
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31.8 Seat tube diameter, what size seatpost?
I'm shopping for a Thomson Elite seatpost on eBay and I see the sizes all over the place: 26.8, 27.2, 30.9, 31.6....which is it? FWIW: The CAAD5 accepts a 31.8 clamp front derailleur.
Thanks
-Jeff
Thanks
-Jeff
04-06-11, 11:39 AM
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i googled seat post diameter for a caad5. i found 27.2.
edit: by the way, i don't have a caad5, this is just what i googled.
edit: by the way, i don't have a caad5, this is just what i googled.
04-06-11, 11:53 AM
#6
Throw the stick!!!!
The tubes can flare from the time it goes from the derailleur to the seatpost. 
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04-06-11, 11:54 AM
#7
Throw the stick!!!!
Have you tried calling Cannondale to ask them? It is going to be next to impossible for anyone that doesn't own (or have experience) with that frame to help you on this one. Tubes can be all different sizes so there is no sure way to know without measuring.
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04-06-11, 11:59 AM
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04-06-11, 12:01 PM
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31.6mm clamp on FD and 27.2 sound reasonable, but i have a raleigh r700 from that era, where the seatpost is most definitely not 27.2, its smaller (i tried to jam a 27.2 post in there and it didn't have a hope in hell) so, i'd say go by the measurement, or stick with the post you already have, it might need a weird size like my raleigh.
and don't even get me started on my 1979 Koga Miyata, its got something like a 26.7mm or some random ass size.
and don't even get me started on my 1979 Koga Miyata, its got something like a 26.7mm or some random ass size.
04-06-11, 12:07 PM
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04-06-11, 12:08 PM
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04-06-11, 12:12 PM
#13
Throw the stick!!!!
But when a tube flares it can bet bigger which means that it could take a 31.8 derailleur but up near the seatpost the tube "could" be 35 or 36 mm on the outside. It all depends on how the bike is designed.
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