Bicycle Mechanics - Rattling aluminum frame?

I have a nearly brand-new Cannondale CAAD9 that has developed an annoying rattle, which sounds like it's coming from within the tubing in the lower down tube/seat tube/bb area. It is audible on rough roads or going over bumps and can be heard when I drop the bike on its wheels from an inch or two up. I can also hear it if I tap the downtube or seat tube firmly.

At first I just thought it was my chain slapping the chainring, but the noise still can be heard when I hold on to or remove the chain. My freehub is tight and I've tried tightening the watter bottle mounts and holding on to the cable housing to no avail. Could this be the bosses for the bottle mounts rattling within the frame? I really have no clue as this is a great and reputable frame that is not known to have any problems...

All I want is my perfectly silent ride back. :(

Could be as simple as a shaving or burr breaking off and rattling in the tubes. Did you remove the seat and see if you could shake something out?

If it is the water bottle bosses, solve it by putting a screw into any unused ones, and tightening.

Could be as simple as a shaving or burr breaking off and rattling in the tubes. Did you remove the seat and see if you could shake something out?

If it is the water bottle bosses, solve it by putting a screw into any unused ones, and tightening.

Yeah, it doesn't quite sound like something moving freely within the frame, but sounds almost exactly like the washer on a presta valve when it's rattling against the wheel. At first I thought it was the chain because it rattles as long as the chain bounces when the bike is "dropped", but I've already ruled out the chain (and because I can hear it by tapping the frame...).

Stupid question, did you check that the end of the FD gear wire isn't anywhere close to the seat tube?

Yeah, I grabbed on to the seat tube and derailleur wire with no luck. Seems internal, if that makes sense? I've found that with chasing noises, it's usually something stupid, so perfectly valid thought!

check seat bag. something in it can be touching causing a rattle.

I've removed my saddle and seat post completely - still there. Pretty soon, I'll be completely rebuilding the bike with a Sram Force group. When everything's stripped off I'll have to do a very thorough inspection, but was hoping to have resolution before then...

Have you checked the water bottle cages? I used a metal cage for a while on my CAAD and any rough roads would cause the cage to rattle...little did I know that rattling caused the cage to crack and then suddenly fail, throwing a caged waterbottle 50 feet in front of me while descending.

I've held onto the cage while giving the frame a drop, still no fix. I believe my bolts are tight enough - I'm afraid to strip the bosses. I can't check now however, as the bike's in the shop getting my Gossamer crankset warranty taken care of. The warranty is on the non-drive side crank arm (which I've also held firm while still getting the rattle) so I don't think this is the source of the noise, but I'll know by Friday. For now, the bottle cage boss rattling internally is my leading candidate; I hope I'm right since that could be fixed with a washer.

The bottle cage riv-nuts can be loose. The shop should be able to fix it if that's the problem.http://www.parktool.com/blog/repair-help/water-bottle-fittings

maybe a cable housing loose in a cable stop?

The bottle cage riv-nuts can be loose. The shop should be able to fix it if that's the problem.http://www.parktool.com/blog/repair-help/water-bottle-fittings

Nice call - I believe this could be the problem based on my symptoms; I'll be giving it a try as soon as I get my bike back from the shop.


maybe a cable housing loose in a cable stop?

This could also be the case, though I've held onto every bit of cable and housing I can think of while still getting the rattle. Nice profile pic, btw...

thanks!
did you check your chain ring bolts? and front and rear skewers?