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Old 08-26-12, 08:18 PM   #1
FreeFloat
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Throwing Chain Off Single Ring

I pulled the small and large rings as well as the front derailler off an old hybrid to turn it into a 7X1, and was shocked to find that while the 7 spd rear derailler and cogs were functioning just fine, as I shifted into the lower gears the chain was being thrown to the inside of the now single speed ring.
Inspection showed a few really worn teeth, could that be the problem?
I had thought a single ring would always keep the links on the teeth no matter what!
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Old 08-26-12, 08:26 PM   #2
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What looks like worn teeth is most likely profiling designed to assist in shifting.
you can either get a single-intended chainring who's teeth are designed to do the opposite -retain the chain.
or you can put the front derailer back on and lock it's limit screws so it acts as a chain guide.
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Old 08-26-12, 08:37 PM   #3
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What looks like worn teeth is most likely profiling designed to assist in shifting.
you can either get a single-intended chainring who's teeth are designed to do the opposite -retain the chain.
or you can put the front derailer back on and lock it's limit screws so it acts as a chain guide.
+1. Even a singlespeed specific ring will not necessarily hold the chain in a 1x configuration if you are running a chain designed for shifting.
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Old 08-26-12, 08:58 PM   #4
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So there are special chains for single speeds? Will it shift properly on my rear cogs?

Never thought that the front derailler was acting as a guide, but now it makes perfect sense.
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Old 08-26-12, 09:11 PM   #5
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So there are special chains for single speeds? Will it shift properly on my rear cogs?
Yes, there are. But i wouldn't recommend them with a 1x7 setup. Unfortunately these setups do suffer from dropped chains without a FD or other chain retention guide. But at that point, how much are you really saving from the 3x7 setup? Two rings and a front shifter. Which is why I rarely setup my bikes this way. Single-speed you can lose enough stuff to make it worthwhile, but IMO as long as you have a cassette and RD you might as well have the extra ring or two and a FD.

Single-speed/fixed gear without a RD (so, using horizontal dropouts) is nice because if you set it up right the chain will never drop.
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Old 08-26-12, 09:20 PM   #6
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The bike had been converted to drops with bar end shifters since there were no braze ons, I switched it back to how it originaly was spec'ed ,.....bought a set of brake levers and only ONE shifter (rear 7) since I thought I did'nt want the high and low rings. I guess I better re-install the front derailer as a chain guide.
Thanks!
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Old 08-26-12, 09:20 PM   #7
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So there are special chains for single speeds? Will it shift properly on my rear cogs?
Probably not. I wouldn't try it.

One one of my 1x9 bikes, I run an MRP 1.x chain guide. On the other I run a bash guard on the outside, and an N-Gear Jumpstop on the inside. I have tried numerous times to avoid the need for a guide, but in the end I've always found that I need something to hold the chain in place.
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Old 08-26-12, 09:28 PM   #8
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Single-speed/fixed gear without a RD (so, using horizontal dropouts) is nice ....
OK, never even thought of this before....but coming from a tandem background....has anyone figuired out a way to convert a normal diameter BB to an eccentric in order to go single speed w/ verticle dropouts?
Personaly I'm not interested, but a smaller diameter cartridge to fit in an eccentric of normal single bike diameter in order to tension the chain? Again, just curious....
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Old 08-26-12, 09:32 PM   #9
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BTW, since you guys are the technical experts, how'd I get to be a "senior member" after only two weeks and just 53 posts?
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Old 08-26-12, 09:34 PM   #10
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What do they use on factory "recreational" 1X7's to keep from derailing from the ring?

Last edited by FreeFloat; 08-26-12 at 09:42 PM.
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Old 08-26-12, 11:10 PM   #11
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Commercially-available 1x__ bikes usually have a "bash ring" on the outer position to prevent throwing the chain off the outside, and the better ones will have a "chain keeper" mounted to the seat tube near the bottom bracket to catch the chain if it drops to the inside. The best thing you can do without those gadgets is to use a SS-specific chainring (taller teeth) and to keep pedaling over bumps -- that keeps tension on the upper run of the chain so it can't fly off as easily.

To answer your other question, 50 posts.
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Old 08-27-12, 08:04 AM   #12
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OK, never even thought of this before....but coming from a tandem background....has anyone figuired out a way to convert a normal diameter BB to an eccentric in order to go single speed w/ verticle dropouts?
Personaly I'm not interested, but a smaller diameter cartridge to fit in an eccentric of normal single bike diameter in order to tension the chain? Again, just curious....
Not a bottom bracket, but an eccentric hub for this purpose:

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Old 08-27-12, 08:14 AM   #13
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Okay I'm confused.. this sounds like a chainline problem to me.. like the same exact problem a friend of mine had. I bow to the superior knowledge of these guys but I'll offer you this, he bought a BB with a shorter length that split the difference placing his chain ring in the center of his cassette via straightline, he runs no bashguard no chain guard, no chain guide, no FD 1x7 on a dually mtb.. I've yet to see him drop a chain since the switch.
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Old 08-27-12, 08:59 AM   #14
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I'll try a new ring for starters, and take it from there.
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Old 08-27-12, 04:26 PM   #15
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OK, never even thought of this before....but coming from a tandem background....has anyone figuired out a way to convert a normal diameter BB to an eccentric in order to go single speed w/ verticle dropouts?
See John's post about the eccentric hub.

I've never used one, but I have converted a few vertical dropout frames to SS/FG by finding the "magic ratio" ie the ratio where you get the perfect chain tension for a given chainstay length. It takes some fiddling but it is possible.
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Old 08-27-12, 04:55 PM   #16
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Chainline......

BTW: Where in the f*** did the OP suggest that he was running his 7x1 without a rear derailleur or even running a SS? He very clearly states that he is running a "7x1", so why the f*** would he want an eccentric BB in the first places!?!

OP: Check your chainline......

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Old 08-27-12, 08:06 PM   #17
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See John's post about the eccentric hub.

I've never used one, but I have converted a few vertical dropout frames to SS/FG by finding the "magic ratio" ie the ratio where you get the perfect chain tension for a given chainstay length. It takes some fiddling but it is possible.
How do you adjust tension as the chain wears(stretches)?
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Old 08-27-12, 08:30 PM   #18
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See John's post about the eccentric hub.

I've never used one, but I have converted a few vertical dropout frames to SS/FG by finding the "magic ratio" ie the ratio where you get the perfect chain tension for a given chainstay length. It takes some fiddling but it is possible.
I had a similar situation w/ my CoMotion Triplet. The midshipman's position also had a child stoker crank attached to an auxillary BB shell clamped to the seat tube. The timing chain from the front went to the eccentric in the middle, which was always compromised between the chain running up and the one running back. One was always too loose! The "magic" link # worked, but with any stretch at all was no longer ok. I only went by symptoms after that, and learned how to forget about worrying about chain tension look or test.
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