Wednesday, June 2, 2010

How to get a loop or (Gordian) knot out of a bike chain

Does your bike chain look like a Gordian knot? Let me show you how to fix it (without cutting!)
Does your chain look like this:


If so read on for a picture guide to unlooping your chain. No special tools needed, although if you're like me, you might want to have a drink before going back out. This happened to me twice, and the second time I decided to find out WHY this happened. I have had up to four loops or knots in my chain at one time. Some would consider it punishment, but I purposely re-created the loops to take pictures for this post. If I could recreate them purposely, I should be able to destroy them purposely.

First, I think it is important to understand exactly how the loop occurs. The bike is upside down, the wheel just taken of. The keys are the pedal and the rear derailleur. If the chain that is normally on the bottom part of the circuit (when the bike is being ridden) gets around the pedal or derailleur, and falls below the chain that is normally on top then your first loop forms.






Now one loop probably wouldn't be too bad, and might be easy to fix. Simply take the chain back up around the pedal. But loops love company. The second loop forms when the back sprocket (derailleur pulley) loses its chain as well.







Now, to fix two loops or knots, you have to take two steps. It is important to get the loops as far away from each other as possible. Most people say that simply by "pushing them into each other" they will go away. This is not true. Step one is putting the back loop up and over the back sprocket, and step two is getting the chain up over the pedal. You will probably have to re-run the chain around the gears by the pedals.

Now, what if you have three or four loops? You can create more than two, but to do this you would have to have twisted the chain as a hole, so that the loops are facing up instead of down.




My unprofessional opinion is that you can only add loops one at a time at this point. you ad them off of the derailleur pulley (rear sprocket). You simply repeat the process from above. Notice, however, that the new loop faces the opposite direction as the first two.




I have had up to four loops in my chain. It was at this point that I considered throwing the bike away and getting a new one. But calm, cool, liquor... I mean collectiveness got me through the situation.

For the future, this can only happen if your bike goes from up and down to sideways. This will usually happen when putting the bike into a car. To avoid this in the future, put the sprocket side of the bike up.

Good luck with your chain!

13 comments:

  1. Hey,

    Good advice on the liquer, helped me conquer it,
    but I used beer instead. And a nice comfy mat
    to solve the puzzle.

    I fixed it by rotating the chain, and putting the chain on the front cogs.

    ReplyDelete
  2. I acquired a couple of loops and persevered until I started to tear my hair out. I came in and searched for chain knots and came up with this very comprehensive analysis. I tried it and it didn't work - probably because I didn't really understand what the OP was getting at. Came in and read it again - none the wiser so I went out and rolled both the loops into one and the konts kind of just disappeared.

    You'd have to think that if they fall into the chain then they will drop out equally easily - always assuming you know what to do.

    The mat works well, but I gave up morning drinking last week...

    ReplyDelete
  3. Many thanks for this exposition.

    I came across the problem last weekend after respraying my son's bike frame (without bothering to remove the chain). Couldn't solve it before dark on the day. Retried this morning with similar fail. Began to suspect a practical joke from someone with a chain splitting tool but googled the problem and was eventually directed here from the TB Stumper forum.

    The problem appears trivial but isn't as simple as making the 2 loops cancel each other by overlapping as the mockers presume! Their turn will come hopefully.

    I'm a design engineer of 20 years and would happily rate myself as an above average problem solver, yet was about to resort to my old chain splitter tool when I gave it 'one last try' following this encouragement and advice. Much more satisfying in the end than 'cheating', but still very hard to articulate the solution.

    Incidentally was discouraged en route by this otherwise great webpage:
    http://www.rain.org/~mkummel/stumpers/27apr01a.htmla
    which specifically classifies it as a Type 2 - Chain knot that can be made and undone only if the chain is not trapped (which it is, by the rear forks)!

    OK, time to get back to what I had previously assured my son would be a very quick job.

    ReplyDelete
  4. You saved my bike's life, I am forever grateful!

    ReplyDelete
  5. thank you thank you! the derailer is still a mess!

    ReplyDelete
  6. I took my knotted chain to my local bike shop and he sorted it for £10...probably the safest and quickest solution for the technically inept.

    ReplyDelete
  7. it worked by making the loops large enough for the pedal to fit through. Got rid of 3 knots, one at a time like this

    ReplyDelete
  8. You mention in your article that pushing the two loops together does not work but it does.....I have fixed this problem a number of times doing just that.

    ReplyDelete
  9. You total hero. Thanks for this.

    ReplyDelete
  10. Thank you so much! I was unpacking my bike after a 10,000 kilometer intercontinental boat trip and it had 2 knots on the chain, I was going crazy. I came up on your blog and this saved me a trip to the local bike shop to get the chain taken care of. I can´t thank you enough really. Keep up the good work!

    ReplyDelete
  11. Pushing my TWO loops INTO one another was EXACTLY what was necessary to free my chain!!! Wtf. No alcohol necessary.

    ReplyDelete
  12. There are two scenarios.
    The case where the two loops are a mirror reflection of each other (as shown in the first picture above) is not fixed by pushing the two loops together. But if they go in different directions, then you can simply push them together as they cancel each other out. You need to look carefully to see which part of each loop is in front of the other where the chain crosses itself. Mine was easily solved by pushing the two loops together after my Bulgarian tour.

    ReplyDelete