# What Size Seatpost Clamp for 30.9mm?



## oliveryou (Jul 31, 2008)

I am looking to upgrade my seatpost clamp as well as my seatpost. The seatpost will be 30.9mm. What size clamp will I need? (http://www.treefortbikes.com/81_333222339112__Lip-Lock-Seat-Collar.html)

Non-quick release version of the Flip-Lock™
Stainless steel pivot
*28.6, 30.0, 30.6, 32.0, 35.0 or 36.4mm sizes*
Black, Silver, Blue, Green and Red
34 grams
Like the Flip-Lock™, but without the commitment issues


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## oldskoolbiker (Jun 2, 2005)

I pretty sure you'll need the 35.0 size


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## CRed (Aug 4, 2007)

oldskoolbiker said:


> I pretty sure you'll need the 35.0 size


Yep I think so too,my 31.6 post uses the 36.4 clamp.


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## Squash (Jul 20, 2003)

*As the others have said....*

it is most likely going to be a 35.0mm clamp that you'll need. However, it can depend on the bike. I have a hardtail with that takes a 27.2mm seatpost, but the required clamp diameter is 35.0mm! My FS bike with a 30.9 seatpost takes the same size clamp. Most bikes with a 27.2 post will take a 30.6 or 32.0mm clamp. It depends on the frame manufacturer in some cases. So it pays to double check it. Either remove the old seat clamp and measure the outside diameter with a caliper or check the old clamp. Many clamps have the clamp iside diameter stamped on them somewhere.

Like I said, you likely need a 35mm clamp, but it doesn't hurt to be sure before you order or purchase one. Not all frames are created equal. :thumbsup:

Good Dirt


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## Captain Chaos (Jan 29, 2006)

What you'll need is a 34.9 seatclamp, which is the accepted standard, but Flip-Lock™ seem to have rounded it up to 35mm.


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## ducktape (May 21, 2007)

Yes most likely 34.9mm 
But it still pays to check. I wanted to trade a bolt on seat clamp with someone that wanted one instead of a qr. Both of our bikes took 30.9 seat posts, but his Specialized needed a smaller (or larger?) seat clamp compared to my Giant which fit 34.9

Take your seat clamp off and measure your seat tube diameter - outer edge to outer edge. It should give you an idea if the size you're looking at is the right one. If you buy a clamp withing 1mm (like 35 instead of 34.9) it should work out fine.


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