Chain coming off too often -advice?

My bike is set up with a single gear in the front, but a full cassette still the back. I didn't use any of the gears (but one obviously) on the crank, so I didn't see any point in having them or the deraileur and took them off. I didn't have any problems at first, but then after my chain came off once, it started coming off all the time. Someone mentioned that I needed to take a link out of my chain to make it just that little bit shorter, but I question their advise for no other reason than who was giving it. Does it make sense to do that? If not, any quick fixes?

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Permalink Reply by dan brown on October 19, 2009 at 8:30am
to do this properly you need a different cog (cassette cogs have tapered teeth) and a special chain
for single speed (thicker). (the cogs are cheap - and West town sells cool colored chains for $7.00)

and spacers too.

it's likely that your "chain line" is off and one of the causes of dropping your chain.

just my $.02
Permalink Reply by Brendan Kevenides on October 19, 2009 at 8:32am
Your chain must be good and taut, though not so much so as to make the bike difficult to pedal. For single speeds and fixed gear bikes this is generally accomplished by sliding the rear wheel backwards or forwards within the rear drops (assuming your bike has horizontal drops or track ends). Unless the chain is extremely slack you shouldn't need to remove any links. If your bike has vertical drops you might have some difficulty getting good chain tension. I think I've seen some chains for sale that have 1/2 links that can be removed to help solve this problem.

The other thing you should consider is your chainline. Does the chain make a nice straight line from your front chainring to your rear cog, or is it a bit twisted? If it is twisted this may contribute to the problem. Go to Sheldon Brown's website for more on this subject.
Permalink Reply by Ryan L on October 19, 2009 at 8:38am
How long have you had this set up? It is possible you have stretched your chain and worn down the rear cog so it is now jumping off due to the worn out teeth. Only way to fix that is with a new chain and new cog. Going to a single speed chain and a single speed cog would help future wear and tear.
Permalink Reply by dan brown on October 19, 2009 at 9:00am
good points. I bought a "half-link" at Cycle Smithy once

Chicago Bicycle Advocate said:
Your chain must be good and taut, though not so much so as to make the bike difficult to pedal. For single speeds and fixed gear bikes this is generally accomplished by sliding the rear wheel backwards or forwards within the rear drops (assuming your bike has horizontal drops or track ends). Unless the chain is extremely slack you shouldn't need to remove any links. If your bike has vertical drops you might have some difficulty getting good chain tension. I think I've seen some chains for sale that have 1/2 links that can be removed to help solve this problem.

The other thing you should consider is your chainline. Does the chain make a nice straight line from your front chainring to your rear cog, or is it a bit twisted? If it is twisted this may contribute to the problem. Go to Sheldon Brown's website for more on this subject.
Permalink Reply by Doug Haynes on October 19, 2009 at 9:23am
Do you still have a rear deraileur? It sounds like you are still using the gears on the cassette, is this correct?

If so single speed chain is not going to be the answer...

Look for worn cogs, stretched chain or a worn out deraileur. You could also have selected a chain ring in the front that leaves you cross geared and prone to tossing the chain in certain gears.
Permalink Reply by PJ on October 19, 2009 at 9:37am
I still use the gears on the cassette, and yes, my setup is definitely crooked and twisting the chain. I had actually put on a different crankset in trying to make my bike lighter and kept the same bottom bracket. Now that I'm actually paying attention, the front chainring is WAY too close to the bike. I think I might need a longer spindle in the BB AND spacers.

I've been trying to do all my own work on my bike, but obviously, I still have a lot to learn. Thanks for your help.
Permalink Reply by wig [ isaac ] on October 19, 2009 at 5:11pm
Permalink Reply by Jackie on October 19, 2009 at 7:45pm
You could get a chain tensioner. Which kind you could/would get would depend on the kind of rear drop outs you have.

I have a chain tensioner similar to this one:

http://farm1.static.flickr.com/204/482502434_c5b63248e8.jpg

It's a really simple component - there are some that are a little more complex though.
Permalink Reply by Doug Haynes on October 20, 2009 at 3:18am
By use the gears on the cassette you mean you still have a derailuer, correct? That's what it sounds like you are saying to me...

If that is the case, and based on what you say about the chain ring, it sounds like you just have a horrible chain line in certain gears and/or your chain is to long/worn.
Permalink Reply by ad on October 20, 2009 at 5:31am
Here are some options if shortening the chain and swaping out the bottom bracket doesn't solve the issue.

First, are you using a single speed chain ring or the old chain ring that came with your original crank? A single speed chain ring will not be ramped (chain rings intended for shifting with front derailleurs have ramps that allow the chain to be pushed off the rings), which would likely help your chain stay on better. A new single speed chain ring can be pretty cheap and might be all you need to help keep the chain on. Here is an example, but you would need to make sure the ring fits your crank: http://www.amazon.com/gp/product/B002G3BK1C

If you are using your old road crank, you can move the chain ring to the middle position (on a triple) or the inner position (on a double) crank. You can then instal a chain keeper on the seat tube to prevent the chain from falling off toward the frame: http://www.competitivecyclist.com/road-bikes/product-components/200...; and instal a bash guard/chain retention ring where the outer chain ring use to be to ensure the chain does not fall off away from the frame (if that is an issue): http://www.webcyclery.com/product.php?productid=17839. People use this type of 1 x 9/10 set up all the time to race cyclocross.

If you are using a single speed crank and chain ring with a cassette/derailleur in the rear and the chain keeps droping, you can use this or something like it to prevnt the chain from droping: http://www.paulcomp.com/chainkeeper.html


Only problem is that the above-mentioned options aren't all that cheap/cost effective.
Permalink Reply by ad on October 20, 2009 at 6:03am
As a side note, if you do decide to try a single speed chain ring to solve the problem make sure you get a chain ring that is designed to work with a 3/32 chain. An 8, 9, or 10 speed chain will only work on a single speed chain ring designed to use 3/32 chains, not 1/8 chains.
Permalink Reply by PJ on October 20, 2009 at 7:02am
Yeah, that is going to be more money I can spend right now. It is a new crank, the old one was an old factory crank that didnt' allow me to take off seperate chainrings. For now, I'm going to concentrate on getting the chainring farter out from my frame to straighten up that chainline. I'll be replacing the chain too, as DUG pointed out it's gotta be stretched and worn from my set up, which is probably why I didn't have problems at first.

Yes, I'm still using the rear derailer, and might have to add the spoon tensioner as mark suggested. Thanks for the suggestions.

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