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Chainring "Boss": What Is This Thing?

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Chainring "Boss": What Is This Thing?

Old 04-15-06, 05:40 PM
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Chainring "Boss": What Is This Thing?

I just replaced a couple of worn chainrings on my old TREK 930. The new large one [46 tooth; 110 mm] had a little cylindrical stainless part thatís threaded on one end. Sure enough, the old one had one of these too that faced outboard and perpendicular to the flat plane of the chainring. When screwed in and tightened, the exposed cylinder is 6mm in diameter and stands out 7mm.

I want to call this little thing a ďbossĒ, but bosses generally guide another part in the right direction.

All I can think is that it somehow aids the experienced biker to somehow re-mount a chain thrown to the outside.

So what is this thing?

Old 04-15-06, 06:01 PM
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Perhaps you could post a picture? If you're describing what I think you're describing then it's to prevent the chain from lodging itself between the crankarm and the outer chainring should the chain get thrown outboard. The crankarm should be over that "nub".
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Old 04-15-06, 06:27 PM
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That little nub will indeed allow an experienced cyclist to pedal a chain, thrown to the outside, back onto the large chainring.

In fact, it will allow an inexperienced cyclist to do the same thing. It is easier to do then you might think. Just keep pedaling and shift gently.

Like Khuon said, mount it so that it is under, or behind the crankarm.
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