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Discussion Starter · #1 ·
without the chain comming off??

I am rebuilding an ol 80 Fuji Sagres into a commuter bike. It has 6 cogs on the back, and a double chainring up front.

I want to know if I can take off the front derailer and the big chainring and still have the bike function?

Thanks...
 

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no problem

KendleFox said:
without the chain comming off??

I am rebuilding an ol 80 Fuji Sagres into a commuter bike. It has 6 cogs on the back, and a double chainring up front.

I want to know if I can take off the front derailer and the big chainring and still have the bike function?
Sure. There are plenty of bikes with single chainrings and rear derailleurs (no front derailleurs). I've had a few myself. This is also a popular set-up for cyclocross bikes.
 

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Discussion Starter · #3 ·
And the chain?

Mark McM said:
Sure. There are plenty of bikes with single chainrings and rear derailleurs (no front derailleurs). I've had a few myself. This is also a popular set-up for cyclocross bikes.
Thank you for your reply. Will the chain be more lily to pop off as I'm shifting the rear gears?
 

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I think it will be a problem...

all of the cx bikes I see like this have a guard on the outside of the ring and a little doo-hickey called a Third Eye Chain Watcher on the seat post.

If you keep the chain as short as possible, have a good strong rear deraileur to keep that chain nice and tight, maybe. Even then, I'd try moving my big ring to the inside of the crank arm and ditching the small ring. Maybe try a nice wide chain, nothing made for 7, 8 or 9 speeds.


But my bets are still on dropping the chain.
 

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KendleFox said:
Thank you for your reply. Will the chain be more lily to pop off as I'm shifting the rear gears?
Not likely. Does it pop off frequently now? Most single chainring derailleur bikes have no additional devices to prevent the chain from falling off because it is not much of an issue.

If you are really concerned about it, you might consider single-chainring chainguards, as used on cyclocross bikes. But chains falling off is more likely on cyclocross bikes because the bikes are frequently lifted up and dropped to the ground (while the racer is in a full run at speed), and the bouncing caused when the bike hits the ground can cause the chain to bounce off. Plus, cyclocross races are short, so 30 seconds lost putting a chain back on can cost a racer many positions. If you don't often drop your bike from shoulder height while running, this shouldn't be an issue for you.
 

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If you are having problems with the chain coming off, and can verify that the problem is a lack of derailer, try changing the chainring to one that is not ramped and pinned to aid shifting.
 

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Discussion Starter · #7 ·
I'm confused

emzed said:
If you are having problems with the chain coming off, and can verify that the problem is a lack of derailer, try changing the chainring to one that is not ramped and pinned to aid shifting.
Not sure what ramped and pinned mean (newbee). I have not had problems with the chain because I've only rode it 4 blocks with everything installed.

I found it with the trash, and took everything off, so I could restore the parts and paint the frame. One I get it put back together I will try it...
 

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I set a bike up this way a couple years ago and I had major problems with the chain coming off- I think the problem was that the chain tension wasn't high enough- I'm betting that to make it work, you'd want to take out some links in the chain so it won't bounce off.

Mind you, while it was a pain in the @$$, it wasn't life threatening or anything. The other problem was that once the chain got chain-sucked one too many times, it just wouldn't stay on for any reason- it'd come off on flat sprints, going uphill, downhill, whenever you looked at it funny...

What I learned from this experience was that the saved weight/cool bike factor of this experiment wasn't really worth the hassle.

I'd suggest a guard on either side of the chain, and then shorten the chain. Or, take the easy route and just don't shift. :D
 

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Discussion Starter · #9 ·
Thanks

What I learned from this experience was that the saved weight/cool bike factor of this experiment wasn't really worth the hassle.

I'd suggest a guard on either side of the chain, and then shorten the chain. Or, take the easy route and just don't shift. :D
Yea I guess your right. But I really wanted to shave 12 ounces off the bike. Thats an extra beer a day I could drink!
 

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There's no reason it should come off. The front derailleur is used to move the chain from the small to the big ring and back. It's not used to keep the chain on the chainring. It can cause the chain to overshift and drop down around the crank arm or the bottom bracket but that's only because it's not adjusted properly. If you're not shifting and the chain comes off it's because of some other problem, not the front derailleur. You can take it off and it will have no affect on whether the chain comes off the chainring, or not. What keeps your chain on the chainring is tension supplied by the rear derailleur. As long as your chain is the correct length and the derailleur provides enough tension there should be no problem. Older derailleurs may have weakened springs and not be able to tension the chain properly. The only way to tell if it will work on your bike is to try it. You've got little to lose but I'll bet a dollar to a donut that it will work ok.

P.S. Why does 12 ounces make a difference to you on a bike being used as a commuter?
 

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I had trouble running that setup, I found that if I kept the chain in the middle of the cassette I was fine, but shifting to or from the edges put me in peril of a drop. Could have been the chainring, could have been worn everything, but the FD helped keep the chain on the ring. I used that setup to ween myself off shifting, so it worked well to my ends. Now that I'm down to one gear no problems!!

I understand one team at the 2005 TdF tried it on team time trial and ran into massive chain-dropping trouble. Don't recall which.

All this having been said, there's no reason it shouldn't work. Just sometimes it doesn't.
 

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Discussion Starter · #12 ·
Not sure

P.S. Why does 12 ounces make a difference to you on a bike being used as a commuter?
Good question, I'm not sure. The bike weighs about 26 pounds stock. I wouldnt save that much weight, I guess I just want to be different...
 

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KendleFox said:
Not sure what ramped and pinned mean (newbee). I have not had problems with the chain because I've only rode it 4 blocks with everything installed.

I found it with the trash, and took everything off, so I could restore the parts and paint the frame. One I get it put back together I will try it...
chances are the existing chainrings have ramps and pins built into it to aid shifting. you can get chainrings that do not have these things and you are less likely to drop a chain off one.
 

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All this being said, you shouldn't let anyone discourage you from doing it- Who knows- you might be the one who figures out how to make it work. Or, you'll have a cool looking bike that occasionally throws the chain. Either way, you get to play with bike parts, and that can never be wrong.

Go for it!
 

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Chains usually come off when shifting the front derailleur (when poorly adjusted).

I see know problem with a single ring up front with a six speed and low cog no bigger than a 24. Just wrap the chain as tight as it will go around the largest cog in back and cut to size. Make sure your pulley cage has good tension, and adjust it if not. You might want to mount the front ring on the inner position if there's room to give you a better chainline in the lower gears.
 
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