# Bang! Chain in spokes!!



## Tel (15 May 2009)

Stacked my fixie last night when the chain came off and went into the spokes locking the back wheel. Unfortunately I was out the saddle at the time so all my weight was over the front wheel which resulted in a very interesting shaped wheel indeed! (photo to follow). 

It appears that the front wheel is the only part damaged, well apart from my elbow and leg  

My question of course is why did my chain end up in the spokes? I presume it is due to my chain alignment?


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## dan_bo (15 May 2009)

chain slack? sounds like a bad 'un that!


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## rustychisel (15 May 2009)

not necessarily but possibly. When you're out of the saddle honking you'd be surprised how much the BB can move laterally, allowing the chain to unship off the chainring, or less often, off the rear cog. This is unusual but combined with a good bump in the road at the wrong time is enough to jump a chain off the cog if it's marginally loose. Even then, the odds are even that it'll go one way or the other. Dunno if a photo will tell you much


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## Joe24 (15 May 2009)

Ive had the chain on my old fixed come off before. It came off front and back so nothing locked up.
It could be due to chainline, slack chain or BB moving.
With mine coming off, i got told by the LBS it was the frame flexing(its a huge frame) but people on here didnt think so.
It had come off twice on the same ride, was tight enough and it just came off on on a little bump one time.
The chain did do a very bad, slack-tight-slack so i put it down to that.
I dont think just the frame flexing with throw the chain off, on my cheapo fixed the frame flexes alot and i put alot of power into it and the chain doesnt come off.
But i suppose that if the chain is slack and the frame is flexing abit and you hit a bump it could throw the chain off.


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## Tel (15 May 2009)

Thanks for the input guys.

I think I might invest in some chain tugs...Also what is the best method for checking the chainline? It looks spot on by eye but there must be a way to check.


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## Joe24 (15 May 2009)

Tel said:


> Thanks for the input guys.
> 
> I think I might invest in some chain tugs...Also what is the best method for checking the chainline? It looks spot on by eye but there must be a way to check.



Stand infront of the bike and look down the chain from the top, using the top tube as a straight edge to compare it to. Thats how i have always checked the chain line, and been told to check it.


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## brodie (15 May 2009)

I think it's almost certainly because the chain is too loose; either the hub hasn't been positioned properly in the dropout so the chain is too loose, or the chainring and sprocket are not round so you get loose spots no matter how tightly you adjust the chain.

I doubt it's frame flex, the bottom bracket moving sideways is not going to really affect the ring to sprocket distance.


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## Joe24 (15 May 2009)

brodie said:


> I think it's almost certainly because the chain is too loose; either the hub hasn't been positioned properly in the dropout so the chain is too loose, or the chainring and sprocket are not round so you get loose spots no matter how tightly you adjust the chain.
> 
> I doubt it's frame flex, the bottom bracket moving sideways is not going to really affect the ring to sprocket distance.



No but it does effect chainline.
You might find its the chainring, or in my case, the axle on my rear hub is slightly bent so it makes a slack spot.


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## brodie (15 May 2009)

For the chainring to centre line measurement: measure the ring to seat tube distance then add half the seat tube diameter. 

Sprocket to centre line distance: subtract sprocket to dropout distance from half of hub OLN.


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## Tel (15 May 2009)

Thanks for the measurements brodie I'll check them. I done some work on my bike earlier, drilled out the dropouts to ensure the wheel could sit further back (old raleigh 501 frame, see other posts). 

Added a couple of links to the chain which I inspected for damage; I found a link which looked slightly damaged so replaced them with the spare I had but on further inspection I found that the chain had a link that had all but completely come away, one side of the link had pulled through. I done some experimenting with my chain breaker and found that it didn't always offer the support required to push the pins all the way through. I've sumised that the pin had not been securely pushed in when I fitted the new chain but was good enough to hold for a while, When I got out of the saddle it stressed the weak link which pulled out and derailed the chain from the chainwheel which made my body fall forward. In retrospect I recall a feeling of "letting go" rather than locking up the back wheel. I think that this is very likely what happened. 

But still checking the bike is set up probably is now high on my priority list just as it always should have been. I now have a new chain breaker tool


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## Joe24 (15 May 2009)

Tel said:


> Thanks for the measurements brodie I'll check them. I done some work on my bike earlier, drilled out the dropouts to ensure the wheel could sit further back (old raleigh 501 frame, see other posts).
> 
> Added a couple of links to the chain which I inspected for damage; I found a link which looked slightly damaged so replaced them with the spare I had but on further inspection I found that the chain had a link that had all but completely come away, one side of the link had pulled through. I done some experimenting with my chain breaker and found that it didn't always offer the support required to push the pins all the way through. I've sumised that the pin had not been securely pushed in when I fitted the new chain but was good enough to hold for a while, When I got out of the saddle it stressed the weak link which pulled out and derailed the chain from the chainwheel which made my body fall forward. In retrospect I recall a feeling of "letting go" rather than locking up the back wheel. I think that this is very likely what happened.
> 
> But still checking the bike is set up probably is now high on my priority list just as it always should have been. I now have a new chain breaker tool



Dont you have a quick link on there to join the chain instead? This is what i always use instead of just joining them.


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## MrGrumpy (16 May 2009)

any unshipping of chains has been purely down to slack chain and nothing else, yes the chainline on my bike is not straight, was pointed out by LBS, who wanted me to invest in new wheels etc and more or less told me my bike just was not suitable  So what i`ve done is bought chain tugs, the wheel no longer slips forward, chain tension is spot on, hasn`t come of yet.


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## Tel (16 May 2009)

Joe24 said:


> Dont you have a quick link on there to join the chain instead? This is what i always use instead of just joining them.



I'm so outta touch. What are quick links? 

Ok heres a few pictures. 

Bent wheel as a result of crash. Spirit level against sprocket/ chainwheel to try to give a visual edge for chain alignment. Other pics of chain alignment.


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## Joe24 (16 May 2009)

Tel said:


> I'm so outta touch. What are quick links?
> 
> Ok heres a few pictures.
> 
> Bent wheel as a result of crash. Spirit level against sprocket/ chainwheel to try to give a visual edge for chain alignment. Other pics of chain alignment.



Can you take a picture of it from the front looking down on the chain? If you get what i mean.
And try and get the top tube and chain not far from each other.
It probably was a slack chain more then anything that caused it.


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## Joe24 (16 May 2009)

Ive looked at that picture and i reckon the chainline is out
I spent a while looking at it, then drew a straight line down from the sprocket and the chainring wasnt perfect. That could just be the angle of the picture doing that though.


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## Tel (16 May 2009)

Thats the problem with taking pictures Joe it can look spot on in some pics and way out in others depending upon the angle. When I look down the top tube the chain line seems to follow the same line. 

As I explained in my post above it appears that the chain link is the culprit for this incident. I sincerely hope it is because I am getting nervous about getting back on it and still have to sort out a new front wheel. I've got a wheel on my good bike that I can use but if it suffered the same fate I'd be gutted...


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## Joe24 (16 May 2009)

Tel said:


> Thats the problem with taking pictures Joe it can look spot on in some pics and way out in others depending upon the angle. When I look down the top tube the chain line seems to follow the same line.
> 
> As I explained in my post above it appears that the chain link is the culprit for this incident. I sincerely hope it is because I am getting nervous about getting back on it and still have to sort out a new front wheel. I've got a wheel on my good bike that I can use but if it suffered the same fate I'd be gutted...



Use a quick link to join then.
Its another outer split in half. One side has 2 pins on which joins the chain, you then put another plate over this and then clip another bit ontop of that. This stops any weak links. You normaly get them with the chains you buy.


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## alecstilleyedye (12 Jun 2009)

i also wouldn't recommend riding fixed with those pedals either…

a clipless (preferable) or at least toe-clip equipped set of pedals will prevent your feet coming off the pedal and getting whacked by the crank, especially when you're spinning away downhill.


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## RedBike (12 Jun 2009)

It's just impossible to tell from the photo if the chainline is straight or not. On the third photo is almost looks like the tyres too wide for the frame. I guess this is just the camera angle again.


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## Joe24 (12 Jun 2009)

Ive rode fixed with flat before. Not gone far or fast though. Going up hill will be a bitch though i would of thought! No way to pull.
I also learnt how to skid with just normal shoes on. 
Take one foot off and try and catch the pedal on the top of your foot when it goes around and lock it
Did it a few times, but you have to get it right.


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