# Seat Clamp Size for Cannondale ?



## carlgorse (7 Jan 2011)

Hello All 

Im thinking about buying a new Seat Clamp for my Cannondale Six , but how do ou find out the correct size ? 

I know it will be above 31.6 as this is my Seat Post size  

Thanks for your help

Carl


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## ColinJ (7 Jan 2011)

If you don't have callipers, improvise some with a large adjustable spanner. Close the jaws of the spanner on the outside of the tubing (being careful not to scratch your paintwork), slide the spanner off and measure between the jaws!


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## Rob3rt (7 Jan 2011)

When the frame is worth that much, you buy some calipers and measure it, or take it to a bike shop and have them measure it. 

Be careful in measuring the right area since if the Six is anything like the CAAD9 then the seatpost is not the same diameter over the whole length, its bigger near the bottom bracket. You will need to take the seat post clamp off and measure, or measure very close to the existing one (well not really, but make sure you at least get on the right third of the seat tube). Why would you ever need to replace the seat post clamp anyway though?  Maybe I'm totally ignorant but it seems like a totally pointless "upgrade".


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## Zoiders (7 Jan 2011)

Clamps stretch over time and the PTFE in the cam wears.

With the post in you can't really damage a seat collar unless you are doing a colar up stupidly tight, I run a 27.2 clamp on a Giant with a larger diameter post and it works just fine.


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## Gerry Attrick (7 Jan 2011)

Go to a Cannondale dealer and get the right part. It's not worth risking a frame for the price of a clamp. 

Cannondale are a bit individual when it comes to frame parts.


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## henshaw11 (7 Jan 2011)

Is this the right model ?
http://www.cannondal...pplement_en.pdf
31.6 post, 34.9 clamp - see last page

- it (and others) are under Support > Manuals & tech notes


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## mickle (7 Jan 2011)

It's all about standards. There are only three sizes of front mech. They are described in metric: 28.6mm, 31.8mm and 34.9. The first two - the oldest - reveal their origin when converted into Good Olde Imperial: One and an eighth - and one and a quarter

*28.6 millimetres = 1.12598425 inches*
*31.8 millimetres = 1.2519685 inches**
34.9 millimetres = 1.37401575 inches*

It follows then that there are just three sizes of seat clamp? For the most part, very occasionally the diameter of the seat tube at the front mech doesn't match the diameter at the seat clamp. This usually occurs when the seat tube is separated in the middle as in 'Y' frame suspension bikes or when the manufacturer butts the tube to reinforce the top of the seat tube junction with the top tube and seat stays. 

Easton's top of the range Scandium alloy tubeset is 28.6mm at the mech and 29.somethingmm at the clamp.

So - except for a very few exceptions there are only three sizes. But if in doubt refer to the manufacturer's instructions!


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## Rob3rt (10 Jan 2011)

mickle said:


> It's all about standards. There are only three sizes of front mech. They are described in metric: 28.6mm, 31.8mm and 34.9. The first two - the oldest - reveal their origin when converted into Good Olde Imperial: One and an eighth - and one and a quarter
> 
> *28.6 millimetres = 1.12598425 inches*
> *31.8 millimetres = 1.2519685 inches**
> ...



My Cannondale CAAD9 is one of these occurances, maybe the Six is similar.

I'd probly invest in a torque wrench if you are planning on tinkering with your carbon frame yourself.


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## carlgorse (13 Jan 2011)

Thanks for all the advice and i think i will just leave it till i get to a good bike store and buy one direct from them 

Carl


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