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Chain derailment more common on ring or cog?

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Chain derailment more common on ring or cog?

Old 04-15-15, 07:35 PM
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Chain derailment more common on ring or cog?

I'm finishing a build with an internal gear hub -- so technically I am posting on the wrong forum. However, since this is a setup with just one ring in front and one cog in back, I think the question is applicable here. When a chain derails on a 1x1 setup, is it more likely to derail on the ring or the cog? I have a bash guard outboard of the ring and a chain-drop preventer inboard, so I am not concerned with chain drop. I chose, however, not to use the dorky looking Shimano IGH cog that comes with a guard on either side of the cog. So I am wondering if I run the risk of chain derailment on the rear cog, or if derailment tends to happen at the ring rather than the cog. I have semi-horizontal rear dropouts and have achieved pretty good chain tension (about 5/8 slack at the loose point and very little slack at the tight point). Chain line is pretty good. I would grudgingly put on the shimano guarded cog in back if I am told that most chain derailment happens at the cog rather than the ring, so I don't have to worry when riding rough bike paths in the middle of nowhere, solo, on tour (C&O Canal/Great Allegheny Passage). What say ye?
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Old 04-15-15, 08:00 PM
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I have lots of 1 x 1 setups, fixed, singlespeed, even IGH. None of them have any kind of chainguards, and none of them have ever derailed on me either front or rear, and I've got more than 5/8" maximum slack on many of them. As long as you've got reasonable alignment between the front and rear sprockets, there should be no problem.
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Old 04-15-15, 09:48 PM
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on fixed: it's most likely to fall off on the inside of your chainring.

on a singlespeed it can fall off anywhere since you can coast.

use 3/32 ring and cog w/ 1/8" if you're worried about chain derailment.

Last edited by sickz; 04-15-15 at 09:52 PM.
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Old 04-16-15, 02:40 AM
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I've never thrown a chain on my SS or FG. I have thrown chains several times on my 3x9 hybrid. Especially when going from 3 > 1 on the Crank... she loves to toss that chain right onto the bottom bracket.
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Old 04-16-15, 08:42 AM
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Originally Posted by motorapido
I have semi-horizontal rear dropouts and have achieved pretty good chain tension (about 5/8 slack at the loose point and very little slack at the tight point). Chain line is pretty good.
Why would you ever drop your chain then?

Stop overthinking it. Instead of asking a bunch of people on the internet, simply ride your bike and see what happens.
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Old 04-16-15, 08:43 AM
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Get a brake.
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Old 04-17-15, 10:35 AM
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Funny thing is I was just about to ask pretty much the same question. After having dropped the chain twice in the past 1.5 months, both times it appears to have dropped off the cog first(yesterday it was still wrapped around the chainring when I stopped) I was wandering the same thing. I know you always hear about it when it drops off the chainring and locks up the wheel. I was wandering if my homemade dropout set up was helping me to drop it off the cog or what. Some answers given thus far have been rather intriguing.
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Old 04-17-15, 11:03 AM
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Originally Posted by bikenh
I was wandering if my homemade dropout set up was helping me to drop it off the cog.
Yes.

*wondering
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Old 04-17-15, 11:08 AM
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#kilott

for serious tho ive never had a chain come off at the back except on a derailleur bike when i dumped 7 gears and hammered on the pedals

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Old 04-17-15, 11:25 AM
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Are your chainline(s) out of bounds? I can't imagine how my chain would ever fall off, when proper tensioned. I have an offset in chainline on 1mm that I'll zero out tomorrow, but even that looks perfect and deadsilent to my ears and eyes. Can't see how it should derail with chainline within bounds.
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Old 04-17-15, 12:51 PM
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Originally Posted by tuxxdk
Are your chainline(s) out of bounds? I can't imagine how my chain would ever fall off, when proper tensioned. I have an offset in chainline on 1mm that I'll zero out tomorrow, but even that looks perfect and deadsilent to my ears and eyes. Can't see how it should derail with chainline within bounds.
Same here. My chainline is off by 1mm at the most, but I use cheap cogs and road cranks/chainrings, so there are way uncool amounts of chain slack at some points of the crank rotation. I keep wondering when that'll cause a dropped chain, but after 4500 miles, I'm not holding my breath either.
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Old 04-17-15, 01:26 PM
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The only times I have dropped a chain on a fixed gear has been due to my own neglect, the chain was way too loose and I was riding on "bumpy" surfaces. This was made worse by having cheap components that weren't very round so chain tension varied as the chain rotated.
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