Chain falling off constantly on 1x8

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Chain falling off constantly on 1x8

Postby robotron » Sat Sep 15, 2012 5:03 pm

Hi there, I'm new here.

So I've got this commuter bike with a 1x8 drivetrain, and the chain comes off like all the time. It usually happens when I am in the highest gears and when going over bumpy stuff. It always falls off to the outside and then sits between the chainring and the chain guard.

What is the simplest/cheapest way to stop this from happening? Someone said that I need more tension in the rear derailler, so i tightened up that screw (B-screw?) which did precisely nothing. I'm thinking of taking some links out of the chain, but I'm not sure how many I can take out without causing problems. This is what my back derailler looks like when the chain is on the largest cog:

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How much chain can I take out? Or is this totally not the best way of sorting this issue out? Any input appreciated. Thanks dudes.
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by BNA » Sun Sep 16, 2012 12:30 am

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Re: Chain falling off constantly on 1x8

Postby eeksll » Sun Sep 16, 2012 12:30 am

firstly it sounds a bit odd that its falling off when you have a chain guard, that should prevent it falling off to that side.

I have this problem and have not found the problem. There are people here who have managed to get it to work, one of the common links with the people who have it working is a longer chain than specified in the shimano docs, it actually looks like yours is long enough.

My "solution" at the moment is by putting on a front derailleur. Used the limit screws to position it right.

Something else I have seen lately that might help is those new shimano XTR derailleurs with a clutch.
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Re: Chain falling off constantly on 1x8

Postby Baalzamon » Sun Sep 16, 2012 7:15 am

You tightened the wrong screw :roll:
B-Limit screw controls the Angle
H-Limit screw controls the outermost limit
L-Limit screw controls the lowermost limit
So what screw do you need to adjust
H-Limit screw.
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Re: Chain falling off constantly on 1x8

Postby bychosis » Sun Sep 16, 2012 7:46 am

My read is the chain falls off the front. IN that case dont adjust the H limit screw on the derailleur.

Looks to me like you could shorten your chain a bit. If the derailleur is hanging well back in the high (smallest) cogs it wont have enough tension. From your pic that looks like where my deraileur sits in probably 6 or 7th on my 1x9. Alternatively you could run a chain guide on the front.
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Re: Chain falling off constantly on 1x8

Postby barefoot » Sun Sep 16, 2012 8:21 am

I don't think it's related to the problem, but that chain is definitely too long.

The chain needs only to be just long enough to shift into the biggest gear you have. That should stretch the derailer cage so the chain runs almost straight from the rear sprocket to the front chainring - with just a little wobble to thread between the jockey wheels. I reckon you could easily lose about 4 links from that chain. There's no downside to having a shorter chain... unless it's so short that you can't shift into bottom gear without breaking stuff. Don't make it that short.

Most 1x setups have some kind of chain guide at the front to hold the chain in place. An old front derailer with the limit screws tightened up is an easy and partially effective option.

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Re: Chain falling off constantly on 1x8

Postby rkelsen » Sun Sep 16, 2012 9:15 am

+1 to shortening the chain.

If you're uncertain, remove one link at a time until you're satisfied.

I was having this exact same problem on my 1x8. Shortening the chain has fixed it without needing anything else, but I have it set up for the best chainline in higher gears.
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Re: Chain falling off constantly on 1x8

Postby jules21 » Sun Sep 16, 2012 11:47 am

are the chainring teeth worn? that will do it
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Re: Chain falling off constantly on 1x8

Postby foo on patrol » Sun Sep 16, 2012 2:07 pm

Looks to me that your chain is to long. :wink:

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Re: Chain falling off constantly on 1x8

Postby robotron » Sun Sep 16, 2012 4:56 pm

Thanks for the suggestions everybody. Think I'll stop by my LBS on the way to work tomorrow and have them take out a few links. Yeah, I'm one of those hopeless cyclists that doesn't like getting their hands dirty.

If that doesn't work I guess I'll try something like this.
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Re: Chain falling off constantly on 1x8

Postby rifraf » Sun Sep 23, 2012 1:22 pm

bychosis wrote:My read is the chain falls off the front. IN that case dont adjust the H limit screw on the derailleur.

Looks to me like you could shorten your chain a bit. If the derailleur is hanging well back in the high (smallest) cogs it wont have enough tension. From your pic that looks like where my deraileur sits in probably 6 or 7th on my 1x9. Alternatively you could run a chain guide on the front.

I disagree.
I think the chain length looks spot on.
See my pics in the lower post. They are will a shadow type derailleur and the perspective isnt quite right in the pic but
the derailluer jockey wheels are almost 90 degrees whilst in the biggest cassette ring.
When I used the earlier XT derailleur the 90 degrees was much more obvious.
I run a single front chainring, 7 speed cassette with 3 speed IGH (rear suspension) and your derailleur mimics the position of my one.
I have no chain dropping issues.
I'd look at if you have a bent derailleur hanger.
It also sounds likely that you've played with the derailleur without being 100% sure of what your doing.
Hey we've all done it and have to start somewhere to learn.
Check out:
http://sheldonbrown.com/derailer-adjustment.html
Pay special attention to what he says about correct chain length about a third of the way down the article.
Sheldons site is a really good one to learn about your bike and maintaining it correctly IMHO.
Good luck and let us know how you get on. :)

robotron wrote:If that doesn't work I guess I'll try something like this.

Highly unlikely you need one of these if your 1x8 setup is original from the factory - is it?

Baalzamon wrote:You tightened the wrong screw :roll:
B-Limit screw controls the Angle
H-Limit screw controls the outermost limit
L-Limit screw controls the lowermost limit
So what screw do you need to adjust
H-Limit screw.
Parktool rear derailler adjustment

Another great site
Last edited by rifraf on Sun Sep 23, 2012 3:24 pm, edited 3 times in total.
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Re: Chain falling off constantly on 1x8

Postby rifraf » Sun Sep 23, 2012 1:32 pm

jules21 wrote:are the chainring teeth worn? that will do it

This and/or a worn chain can cause your symptoms.
You dont say how old your bike is or its running gear.
You dont say whether the symptoms are new or if they started after you'd changed anything.
Go through the processes outlined in Sheldons site to check out chain and gear wear, correct chain length and
correct derailleur adjustment and let us know the outcome. :)
Good luck
Last edited by rifraf on Sun Sep 23, 2012 3:11 pm, edited 1 time in total.
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Re: Chain falling off constantly on 1x8

Postby rifraf » Sun Sep 23, 2012 1:53 pm

rkelsen wrote:+1 to shortening the chain.

If you're uncertain, remove one link at a time until you're satisfied.

I was having this exact same problem on my 1x8. Shortening the chain has fixed it without needing anything else, but I have it set up for the best chainline in higher gears.

Satisfied? :shock:
I dont get it.
I'm not sure this is the best advice for some one who is new to cycle mechanics.
He could end up discarding his whole chain searching for "satisfaction".
Was the Rolling Stones playing when you typed this? :wink:
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Re: Chain falling off constantly on 1x8

Postby rifraf » Sun Sep 23, 2012 2:01 pm

barefoot wrote:I don't think it's related to the problem, but that chain is definitely too long.

The chain needs only to be just long enough to shift into the biggest gear you have. That should stretch the derailer cage so the chain runs almost straight from the rear sprocket to the front chainring - with just a little wobble to thread between the jockey wheels. I reckon you could easily lose about 4 links from that chain. There's no downside to having a shorter chain... unless it's so short that you can't shift into bottom gear without breaking stuff. Don't make it that short.

Most 1x setups have some kind of chain guide at the front to hold the chain in place. An old front derailer with the limit screws tightened up is an easy and partially effective option.

tim

Hi Tim,
I "think" your advice flys in the face of both shimano docs and any
online advice from sites like Sheldons, Park etc. (that I've read).
It also flys in the face of manufactured bikes that have single chainring setup from the factory (that I have seen)
The OP (original poster) doesnt mention having recently added links to his set up so why would you imagine that a bike
suddenly starts throwing chains due to too many links?
Your "The chain needs only to be just long enough to shift into the biggest gear you have" and "Most 1x setups have some kind of chain guide at the front to hold the chain in place" just isn't correct in my opinion (how ever well intentioned).
Image
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Image
Image
Image
I rode my bike from Mudgee to Adelaide and then on to Perth, towing a trailer, where I am now.
Not once did my chain fall off.
It is adjusted as per instructions from Sheldon Browns website after I read docs from both shimano and sram
to confirm that they concur.
My bike uses a sram chain and shifters and shimano cassette, derailleur and chainring.
With its dual suspension, if anyone should have chain drop issues its me - doesnt happen :!:
I even "upgraded" my cranks from a single chainring version to a dura-ace double (still using only one ring).
I had to spend time getting the "chainline" (see Sheldon) in the right (as per docs) position so I could
get correct rear derailleur position.
Before I got the right I had noisy gearing lost the ability to change to the smallest cogs on the cassette.
When someone told me to check my chainline via Sheldons site, I did and have never looked back.
I once had chain dropping issues due to a bent derailleur hanger.
A relative had moved my bike and let it drop bending the hanger without telling me.
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Re: Chain falling off constantly on 1x8

Postby rifraf » Sun Sep 23, 2012 4:25 pm

eeksll wrote:firstly it sounds a bit odd that its falling off when you have a chain guard, that should prevent it falling off to that side.

I have this problem and have not found the problem. There are people here who have managed to get it to work, one of the common links with the people who have it working is a longer chain than specified in the shimano docs, it actually looks like yours is long enough.

My "solution" at the moment is by putting on a front derailleur. Used the limit screws to position it right.

Something else I have seen lately that might help is those new shimano XTR derailleurs with a clutch.

Did you ever get around to getting your chainline checked as suggested in your thread on this issue
Once again:
http://sheldonbrown.com/chainline.html
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Re: Chain falling off constantly on 1x8

Postby rkelsen » Sun Sep 23, 2012 9:05 pm

rifraf wrote:I'm not sure this is the best advice for some one who is new to cycle mechanics.

I like to give people some credit for intelligence. He posted on here about shortening his chain, so I figure he can't be a complete numpty.
rifraf wrote:He could end up discarding his whole chain searching for "satisfaction".

:roll:
rifraf wrote:Was the Rolling Stones playing when you typed this? :wink:

No.
rifraf wrote:I disagree.
I think the chain length looks spot on.

Sheldon Brown says:
"The best technique for setting chain length is to thread the chain onto the large/large combination, without running it through the rear derailer. Mesh the two ends on to the large chainwheel so that one complete link (one inch, -- one inner and one outer half-link) overlaps. In almost all cases, this will give the optimum length."
I'm willing to bet that this advice would result in a shorter chain than the OP has now. At least 2 links shorter.
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Re: Chain falling off constantly on 1x8

Postby rifraf » Sun Sep 23, 2012 10:36 pm

rkelsen wrote:I like to give people some credit for intelligence. He posted on here about shortening his chain, so I figure he can't be a complete numpty.

I agree

rifraf wrote:He could end up discarding his whole chain searching for "satisfaction".

:roll:
rifraf wrote:Was the Rolling Stones playing when you typed this? :wink:

No.[/quote]

Hope you read my intended humour in this.
Sorry if you didnt

rifraf wrote:I disagree.
I think the chain length looks spot on.

Sheldon Brown says:
"The best technique for setting chain length is to thread the chain onto the large/large combination, without running it through the rear derailer. Mesh the two ends on to the large chainwheel so that one complete link (one inch, -- one inner and one outer half-link) overlaps. In almost all cases, this will give the optimum length."
I'm willing to bet that this advice would result in a shorter chain than the OP has now. At least 2 links shorter.[/quote]

I'm hoping that the OP gives us an update and proves us all a little right.
On the other hand, I've been wrong before and will happily admit it if its the case this time.
What ever the outcome I'm hoping for a good resolution for the original poster. :)
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Re: Chain falling off constantly on 1x8

Postby barefoot » Tue Sep 25, 2012 11:51 am

rifraf wrote:
barefoot wrote:I don't think it's related to the problem, but that chain is definitely too long.

The chain needs only to be just long enough to shift into the biggest gear you have. That should stretch the derailer cage so the chain runs almost straight from the rear sprocket to the front chainring - with just a little wobble to thread between the jockey wheels. I reckon you could easily lose about 4 links from that chain. There's no downside to having a shorter chain... unless it's so short that you can't shift into bottom gear without breaking stuff. Don't make it that short.

Most 1x setups have some kind of chain guide at the front to hold the chain in place. An old front derailer with the limit screws tightened up is an easy and partially effective option.

tim

Hi Tim,
I "think" your advice flys in the face of both shimano docs and any
online advice from sites like Sheldons, Park etc. (that I've read).
It also flys in the face of manufactured bikes that have single chainring setup from the factory (that I have seen)


Then it seems you're not very familiar with 1x9 and 1x10 mountain bike setups - especially popular in downhill and "all mountain" disciplines.

Chain guides are absolutely standard fitment there:
Image

Of course, these are fairly abnormal conditions, and far more prone to dropping chains than any kind of road riding... but the fact is that these guys had a problem with chains falling off, and over many years, this style of chain guide has become the standard solution. I don't know of many mainstream non-MTB bikes that are available with a 1xn drivetrain, but those I've seen usually have a less severe version of the same theme (usually without the bottom pulley), or solid guide rings on either side of the chainring (looking like the old ring-mounted chain guards that used to be fitted to 10-speed road bikes).

Chains only fall off when they go slack on the top run. The less excess chain you have flapping around the bottom run, the less chance there is of your top run going slack while coasting and trying to exit when you begin pedalling again.

I race in my local club's "dirt crit" series - basically a short-course cross-country MTB race format. When my ancient 3x8 drivetrain was in the process of falling to bits last year, I converted briefly to a 1x8 setup without a chain guide. Briefly, because I was dropping my chain about once every lap (~1km), even though my chainline was good (chainring lined up with the mid-block gears I was using most). Others manage successfully with a chain guide to help keep the chain on (I solved my problem by getting a new bike :oops: )

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Re: Chain falling off constantly on 1x8

Postby rifraf » Tue Sep 25, 2012 12:55 pm

barefoot wrote:Most 1x setups .....


I think it was your words "Most" that caught my eye

barefoot wrote:Then it seems you're not very familiar with 1x9 and 1x10 mountain bike setups - especially popular in downhill and "all mountain" disciplines.

True, you'd be 100% correct there

barefoot wrote:Chain guides are absolutely standard fitment there:
Image

Of course, these are fairly abnormal conditions, and far more prone to dropping chains than any kind of road riding...

Probably more from where I'm coming from

barefoot wrote:but the fact is that these guys had a problem with chains falling off, and over many years, this style of chain guide has become the standard solution. I don't know of many mainstream non-MTB bikes that are available with a 1xn drivetrain, but those I've seen usually have a less severe version of the same theme (usually without the bottom pulley), or solid guide rings on either side of the chainring (looking like the old ring-mounted chain guards that used to be fitted to 10-speed road bikes).


I travel in different circles but your experience is still valid

barefoot wrote:Chains only fall off when they go slack on the top run. The less excess chain you have flapping around the bottom run, the less chance there is of your top run going slack while coasting and trying to exit when you begin pedalling again.

I race in my local club's "dirt crit" series - basically a short-course cross-country MTB race format. When my ancient 3x8 drivetrain was in the process of falling to bits last year, I converted briefly to a 1x8 setup without a chain guide. Briefly, because I was dropping my chain about once every lap (~1km), even though my chainline was good (chainring lined up with the mid-block gears I was using most). Others manage successfully with a chain guide to help keep the chain on (I solved my problem by getting a new bike :oops: )

tim

I think I was unsure where you were coming from, keeping in mind you didnt mention it and the OP's bike looks to be
not a racing MTB so I offered my opinion
In fairness to your post, most of my experience is with smaller wheeled bikes of a non MTB racing nature.
In fairness to mine many of them are full suspension and long chainstay which accentuates chainsuck and bobbing motion.
Think Birdy, Bike Friday, Tern, Dahon and Moulton to name a few.
None of the mentioned (last I looked) utilise any chain guide.
All have models with single front chain ring and rear cassette and derailleur like mine.
Interesting to see your pic and to be informed about the new commonness of the guide setup.
You (I) learn something every day - thank you for that.
On a side note, I had for many years a 26' wheeled Mountain bike and I used Sheldon Browns chain length
doc's to find the right length.
On my mountain bike as well (sold now), when in the lowest gear (most teeth gear on the rear cassette) my rear derailleurs
jocky wheels were in basically almost a verticle position rather than stretched out almost horizontal like I see
on many bikes whose owner have lots of drive train problems.
I believe it should be possible to someone to have a 1x set up without issue for the reason that I experience it myself
every time I get off my fat lazy butt and ride my bike.
I doubt the OP's bike, if its factory, started it life throwing chains.
I dont think guides are a bad idea per se' but think his problem is likey he's either changed something or bent something
to make his bike no longer the same it was when it was first pushed from the display window in the LBS.
Nice to hear your angle on things and your experience.
I think hearing it the answer is we are both right from our points of view.
I'm looking forward to the OP updating us on whether his bike is factory, the chain and chainrings in good condition, whether
he's changed anything and has the issues been rectified.
Hopefully all will be reveled :D
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Re: Chain falling off constantly on 1x8

Postby robotron » Mon Dec 10, 2012 9:00 pm

I was just sitting there watching the TV and then for some reason I remembered that I never replied to this forum thread from like three months ago. And for some reason I decided it was really important to do so.

So I did end up getting one of these.

It works like an absolute charm. I had to take an angle grinder to the chain guard to get it off, as it was a permanent part of the chainring for some reason. I removed a tooth by mistake. But I've never had any problems with the chain falling off since.

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Re: Chain falling off constantly on 1x8

Postby ironhanglider » Wed Dec 12, 2012 7:09 pm

Thanks for the update robotron. Must say that the chainring in the photo is significantly worn. If your chain is new it is being worn prematurely to suit the old chainring, this will also wear out the cassette prematurely. If the chain and cassette are similarly worn then you might as well use them until the chain starts jumping under load in your favourite gears. Then you'll be up for a whole new chain, cassette and rings.

I'd actually be surprised if the chain guide is necessary with a new drivetrain.

Cheers,

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