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I heard once that you should clean your chain with a light degreaser whenever it looks especially dirty or at the very least once every few months. But that doesn't account for frequency of rides or miles ridden!

I've been riding my road bike over 100 miles per week for the last month and have been meaning to clean my chain anyway... and then...

The past week my chain kept popping off the chainrings. Four times out of five it was while shifting from the small ring to the big one. I believe it also happened when accelerating from a pretty low speed, like just at the crest of a very steep hill.

I'm going to clean my chain anyway, but I'm just curious: could a very dirty chain be causing it to pop off the rings? Or could this be a problem of technique? Or do I just need a general tuneup?

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In addition to the answers below, if this is on a new bike, then after a few hundred miles the cables and housings will break-in and possibly stretch a bit, causing shifting problems. Usually after re-adjusted after initial break-in, then they stay much better. –  rally25rs Sep 10 '11 at 20:39

3 Answers 3

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No. A greasy chain won't cause the chain to pop off, and it would have to be exceptionally dirty for dirt to cause this. (I've ridden many miles with greasy, dirty chains.) Generally a chain comes off due to maladjustment or because of a worn component (usually a cog).

Poor technique can contribute to the problem, but the technique either needs to be pretty bad or there needs to be another contributing factor.

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The last couple of weeks I've been playing close attention to shifting technique, especially right before the chain pops off as it has continued to do so occasionally. I believe I found a pattern and can recreate it pretty consistently: the chain pops off when I'm in the one of the smallest rear cogs and the small chain ring and then shift to the big ring. –  mark Sep 25 '11 at 20:55
    
Yes, I was having pretty much the identical problem. It was a combo of maladjustment (of the bike, not the rider) and a worn-out front ring. Carefully up-shifting on the front could avoid it, but if I thought about it too much that made it worse (apparently because I was holding the shift lever too long). –  Daniel R Hicks Sep 26 '11 at 2:07
    
Bent rings can also cause the chain to fall-off. Big ring is specially prone to get bent from hitting any hard object. Just a thought. –  heltonbiker Nov 4 '11 at 11:51
    
True. But a bent ring is fairly easy to spot, if you observe it closely while turning the crank. Look for both the ring wiggling back and forth as turned, and for individual dinged/broken teeth. –  Daniel R Hicks Nov 4 '11 at 12:05

Does it pop off the outside of the big ring? If so, then the outside limit of the front derailleur probably needs to be brought in. If it's falling off the inside the it might not be "picking up" properly. Like Daniel says, poor technique (like up-shifting under heavy load) can cause this.

I don't think fully degreasing your chain is a good practice. I think its better in most cases to simply apply more clean lube than stripping the grease out first. A clean chain is awesome to look at but doesn't necessarily perform better than a properly lubed (but grey) chain.

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Yes, too much grease can pop chains, especially when shifting gears. When I first started biking seriously, I thought lots of grease was a good thing because it made the pedaling feel smooth. That was a bad idea. I got stranded in the middle of nowhere with my chain constantly slipping off so bad that the only choice was to ride the same gear or remove the grease. I used a spare cleaning cloth to wipe off most of it and it was fine the rest of the ride.

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