Bicycle Mechanics - Feel stupid - chainring Q

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JAJ0404
09-16-12, 07:25 PM
I changed my small chainring, and when I was putting it back together I noticed the small knob on the outside of the large chainring. I had noticed it before, but never paid much attention to it.

Real question - does this knob need to be lined-up up with anything?

Curiousity question - what's the purpose of this little knob?

Homebrew01
09-16-12, 07:41 PM
The knob should be next to the crankarm. It prevents the chain from getting jammed between the arm and chainring if you overshift.
prathmann
09-16-12, 07:41 PM
If it's the one I'm thinking of then the purpose is to keep a dropped chain from getting wedged between the crankarm and the spider. It should be lined up with the crankarm so it fills that gap.

Reynolds
09-16-12, 07:42 PM
It goes behind the crankarm. It's there to avoid chain jamming if the chain falls.
JAJ0404
09-16-12, 07:49 PM
Thanks guys, of course that's where I had it, and before I tightened everything, I said 'that can't be right' and I moved it from behind the crank. If I could harness all the extra work I've caused myself in my lifetime - - - I could retire.