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Discussion Starter · #1 ·
Good morning everyone. I just bought a leftover 2013 F29 Lefty and the fork doesn't hold air. It leaks about 20 pounds of pressure after every ride. I thought I read somewhere, on the Lefty section, that I should turn the bike upside down and let it sit a while.

Can anyone elaborate on this please?

Thanks,

Tom
 

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Hybrid Leftys aren't real
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That's old advice. Current gen forks like yours won't benefit from that.

Check that your valve core is tight, I'd also pull the air plug (after letting the pressure out of course) and see that the seal on it is in tact, they do sometimes catch and tear upon installation.

Beyond that, you're best to take it to where you bought it, and have them pull the damper and swap seals, they also, can catch and tear occasionally, on installation.

Easy initial check? Air it up to say, 200, and wipe some soapy water around the bottom where the air goes. Bubbles? You found your leak point. No bubbles? Back to the shop for the above....
 

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Yup,
Couple of years ago had the same issue with a new DLR and it was the easily fixable " valve core " .
Wrenches can be found at Walmart or any hardware store.
 

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Two things first. Snug the core with a core tool, and snug the plug with a socket.

Still bubbling from both? Release pressure, replace core, unscrew plug, replace seal, repeat test.

A bit of grease will help snug smoothly, but is in no way a leak preventer.....
 

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Discussion Starter · #6 ·
Thanks. I'll definitely check it. Any idea what size socket I need? I don't have one large enough at home.
 

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24mm, and be careful, those wrench flats are fragile, and thin. Good downward pressure during the initial "cracking" will save a lot of head banging on wall.....
 

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Discussion Starter · #9 ·
Thanks. Took the cap off, cleaned and re-greased it and problem solved.

I have another idiotic question if you don't mind. My F29 has a 27.2 seat post. What is the outer diameter of my seat tube? 28.6 or 31.8? Thanks again.
 

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Cannondales were 31.8 for years, some road frames in recent years have bumped up to 34.9 though, despite remaining at 27.2 post diameter. Additional swaging for BB stiffness would be my assumption.

My guess would be 31.8, but I don't sell the bike brand, so measuring is the best way. No way is it 28.6 though....

If you're buying a new FD, just buy a 34.9 as they all come with shims nowadays anyway.
 
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