Bicycle Mechanics - noise from my crank

I just got my bike put togeher.. but I am having a strange problem. When I have it in the smallest front and rear gear, I get this metal hitting metal.. I know it is the chain, since if I put slight pressure on teh chain pushing it in towards the bike it goes away. It is not hiting the de-railer, I am positive of that. When looking straight down on the crank from above, when I turn the crankarms.. it appears that the chain goes in slightly every couple inches causing it to hit the larger chainring. Anyone have any ideas what is causing this? This is my first time to put a bike together from scratch, so might be a stupid mistake I made.
..kevin

are you fair dinkum or just being a dill, crikey mate , wake up and smell the fosters !!! :confused:

If I understand correctly, you hear a metallic rubbing when you're in small/small, right? That's chain rub. It happens to everyone, with every bike. Your chain is rubbing [hence the name] against the fron derailleur. All it means is that you shouldn't use the small chainring/smallest cog combination. You won't die if you do, but you'll put wear on the chain and front derailleur.

In other words, it's normal.

[You may never have heard it before because alu bikes like the GT tend to conduct sound much more efficiently than other frame materials.

Particularly if you have either three chainrings or at least 6 cogs, do not ride in either large-large or small-small. However, small-small is the ideal long-term storage gear, since it minimizes tension on all derailleur springs.

On most bikes, adjusting the chainline to eliminate rub in small-small will make your large ring work smoothly with only the smallest cogs. Today's fashionably large (14T) chainring steps exacerbate chain rub.

IT's not rubbing the de-railer that is the strange part.. I made sure of that.. it is only a double chainring, it is like the chain is slightly wider in parts and causing it to actualy hit the larger ring, which causes a nice ring like noise, if you tap your outer ring with somethign metal it makes the same sound.. it is very slight. I am running a 10-speed rear.. Campy record. with dual chain ring front campy record.

Originally posted by Kev
IT's not rubbing the de-railer that is the strange part.. I made sure of that.. it is only a double chainring, it is like the chain is slightly wider in parts and causing it to actualy hit the larger ring, which causes a nice ring like noise, if you tap your outer ring with somethign metal it makes the same sound.. it is very slight. I am running a 10-speed rear.. Campy record. with dual chain ring front campy record.

Does it only rub the outer chainring when you are in the smallest cog at the back? If so, then that is to be expected due to the 13T or 14T diference between the two rings. And yes, it is possible for the chain to rub on the outer chainring without rubbing on the derailleur. Frankly, I would be surprised if it didn't rub the large chainring while on the two smallest cogs at the back since the chainrings are spaced even closer together than with the 9-speed.

http://www.campagnolo.com/qea_search.php?gid=1&cid=7&key=comp

If you are wondering why it only rubs during a small part of the overall revolution it is because there is always going to be some eccentricity in the chainrings no matter what. If it drives you nuts you could very gently try to bend the chainring outwards in the exact place where it rubs. It's up to you.

Quit using that gear combo and you'll quit hearing the noise.
Seriously, the small to small gear combo is one you should avoid, the extreme chain angle causes undue wear.
My chain rubs in that combo too.

Ride good gears
Pat

Yeah, the chain is rubbing against the large ring. That's because you are not supposed to be in that gear! Never, never, never ride in the small-small or large-large combination on any recent road bike. The chainline is way out of whack, and you will be putting the rings and cogs under tremendous lateral forces.
Some bikes, especially those with more severe 14-tooth gaps between the rings may even rub in the next cog, too. If so, this gear combination should also be avoided.

Thank you for everyone's help. This being my first bike I have built.. I thought I had done soemthign seriously wrong, and just wanted ot double check with everyone out there.
Merry Christmas!

When in doubt, do your best to keep the chain as straight as possible