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I need to know the seat tube diameter on my 09 Cannondale F7. I can’t find it on the website anywhere. My front derailleur is broken and I need to buy a new one. I don’t want to get one and have it be too small to fit around the tube. Can anyone help me out?
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I’m pretty sure it’s 31.8mm in outer diameter. You quickly can be sure of this number by measuring a piece of string wrapped around it. You’ll need an 8 speed compatible front derailluer. Both SRAM and Shimano make one. Both should also work with your shifters if they are the stock X-4s. Most of SRAM and Shimano’s front derailleurs now come with a clamp kit to cit different size seat tubes as well. The stock model on that bike is the SRAM 3.0 if you just want to get the same one that is on there right now.
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The bottom of the tube should have the diameter size stamped into it. If you are buying a new one from a LBS just bring it in. String thing will measure circumfrence not diameter.
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Golden goose is correct the higher end derailleurs usually have (with them) adapters to accept multiple tube diameters….Or you could simply use a tape measure in metric and measure its circumfrence and divide by 3.14…The answer is your diameter…Simple.
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As Goose said, it should be 31.8 OD.
Word is that all cannondales use 27.2ID/31.8OD seat tubes.
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f7 spec says it has a kalloy sp-359 seat post, 31.8mm
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Another trick is to remove the failed derailleur and see what size it is. 😉
Most derailleurs will have their clamp size stamped inside the clamp, and I can say for sure that Shimano XT models come with shims for multiple seat tube diameters, as mine did.
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