Problem with small chainring on triple cranks

[cakake]

I've recently put together a bike with a triple crank on it. Everything seems to be working well, except when the chain is on the small chain ring up front. The chain doesn't release from the small chain ring when pedaling. Here's a picture:

http://www.millsisland.net/gallery/album11/P5060058
http://www.millsisland.net/gallery/album11/P5060059
http://www.millsisland.net/gallery/album11/P5060060

Looking at it from the top, the small chain ring is *very* close to the middle chain ring.

http://www.millsisland.net/gallery/album11/P5060062
http://www.millsisland.net/gallery/album11/P5060063

The protrusions on the inside of the middle chain ring are what the chain is hanging up on when on the small chain ring. With a bit more space, I don't think this would happen.

It's an Ultegra crank with a Shimano hg53 9 speed chain. It happens no matter what rear cog the chain is on. I've adjusted the limit screws and that isn't it.

Any suggestions as to what's happening?


Eric

 

[cakake]

After pulling the crank and looking at it, I figured it out. The small chain ring was on backward. I'm not sure how that happened....


Eric

 

[alfeng]

After pulling the crank and looking at it, I figured it out. The small chain ring was on backward. I'm not sure how that happened....

Eric

Well, you noticed that granny was mounted backwards just as I was about to "submit" my reply -- I was going to mention (and, I will now, for others) that the recess is to allow the chainring bolts to sit flush against the chainring ...

The difference can be almost 1mm in separation between the granny and middle chainrings when the granny is reversed.

Additionally, your middle & granny rings are not oriented properly as seen in PICTUREs 2 & 3 -- that small "nub" that the chain is caught on is a "registration" key -- you want the "registration" key to be aligned with the protruding PIN on of the largest chainring which is hidden by the crankarm ...