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What size front derailleur clamp do I need?

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What size front derailleur clamp do I need?

Old 06-17-11, 01:34 PM
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ncrain1
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What size front derailleur clamp do I need?

I am putting a new group on my bike and need to know what size front derailleur clamp I need. I have a scott S30 and on their website it lists the seat post as: Scott Alloy 31.6/300 mm would that mean I need a 32mm clamp? Thanks in advance for any help, I truly appreciate how helpful so many of you are!
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Old 06-17-11, 01:38 PM
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Originally Posted by ncrain1 View Post
lists the seat post as: Scott Alloy 31.6/300 mm would that mean I need a 32mm clamp?
No, 32 would be too small. Think about it. The only way to be sure is to measure it with calipers.
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Old 06-17-11, 01:39 PM
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Originally Posted by ncrain1 View Post
I am putting a new group on my bike and need to know what size front derailleur clamp I need. I have a scott S30 and on their website it lists the seat post as: Scott Alloy 31.6/300 mm would that mean I need a 32mm clamp? Thanks in advance for any help, I truly appreciate how helpful so many of you are!
It's probably either 31.8 or 34.9. Those are the two most common sizes, I believe, with the former being the most common.
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Old 06-17-11, 01:52 PM
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You will need a 31.8 clamp on FD.
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Old 06-17-11, 02:15 PM
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Unless there's some wacky tapering going on, a seat tube that takes a 31.6 post will almost certainly take a 34.9 clamp for the FD. Remember that the seat post size is measured by the INNER diameter of the tube, and the FD clamp is measured by the OUTER diameter of the tube it's clamping on to.
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Old 06-17-11, 02:25 PM
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Originally Posted by tagaproject6 View Post
You will need a 31.8 clamp on FD.
This is very wrong.

Go with what Doc Pete prescribed, if you are using a 31.6 seatpost, you use a 34.9 clamp. Not unless you have a braze on, then use a braze on FD.

UPDATE: I just looked at the scott website, they use a 34.9 braze-on adapter with a braze-on FD. This just gives you more options like moving your FD to a diff bike.

Last edited by giantdefy; 06-17-11 at 02:44 PM.
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Old 06-17-11, 02:38 PM
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Originally Posted by giantdefy View Post
This is very wrong.

Go with what Doc Pete prescribed, if you are using a 31.6 seatpost, you use a 34.9 clamp. Not unless you have a braze on, then use a braze on FD.
Oops...sorry. Reading fail
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