How to prevent chain falling off while pedalling?

[Thursday guy]

I was cycling today, changed gears on the front chainring, and suddenly I felt no power in my pedal strokes. It turns out that the chain at the front end 'slipped' out of the cogs and onto the pedal bracket.

It happened as I changed gears on the front chain ring, although I can't remember if I was changing up or down. Anyway, how do I prevent this sort of thing from happening? Is it a case of lubricating the chain because come to think of it, I haven't lubricated the bike in ages.

 

[mjr]

Check the limit screw settings and check your chain for wear, as well as lubricating it. It sounds like the shifter moved the chain too far for some reason.

 

[Slioch]

Should be an easy enough problem to fix, Have a look at sections 4. & 5. on this link.

http://www.parktool.com/blog/repair-help/front-derailleur-adjustment#article-section-4

 

[Sharky]

Check also the cassette free hub. Mine started sticking and carried on turning when I was freewheeling, forcing the chain to drop off the chainring.

 

[boydj]

Assuming that the limit screws are properly adjusted, then best not to change chainring when the chain is on either extreme end of the cassette. If you have to do this then move the front shifter fairly slowly and keep the pedals moving smoothly.

 

[Dogtrousers]

Also, avoid riding in the big chainring and biggest cog at the back (ie cross chaining) then dropping down to the little ring. This is more likely to cause the chain to come off inwards (I know from experience).

Edit: @boydj beat me to it ... just.

Note also that as long as you have a bit of momentum you can often put the chain back on just by pedalling gently and using the front mech. No need to stop and get oily fingers. This is easier with old fashioned friction shifters than brake lever shifters but it's entirely possible with both.

 

[raleighnut]

^^^^^^^+1 and doubly so for using the front mech to pick up the chain.

 

[earlestownflya]

dropping chains happens from time to time,can be a few things,limit screw on the front mech,poorly maintained chain,chain too long or stretched,or sometimes the rear mech doesn't pick up the slack as quick as you'd like. especially if the springs getting tired..even happens to the pro's..

 

[MichaelW2]

Also check the position and orientation of the front mech. Old, worn mechs can mis-fire.

 

[deptfordmarmoset]

If it happens again and the limiters appear to be correctly set, a ''dog fang'' can help. (Note: you'll need to know the diameter of your seat tube.)

 

[Dogtrousers]

^^^^^^^+1 and doubly so for using the front mech to pick up the chain.

When riding with others, on a couple of occasions people have seen me do this and been amazed at my chain-related super powers. What skills! I hate to tell them that it's incredibly easy and the reason most people stop to put their chain back on is because they simply haven't thought of asking the bike to do it for them. It comes from years of riding bikes with wonky chainsets, and badly fitted (by me) and badly adjusted (by me) derailleurs.

 

[Profpointy]

do check that the chainset isn't wonky - not as likely as the most common cause of poor adjustment but has been known. Spent hours unsuccessfully getting my old bike to stop throwing chains before spotting the wonkiness - the solid BB axle was actually bent somehow.

 

[earlestownflya]

do check that the chainset isn't wonky - not as likely as the most common cause of poor adjustment but has been known. Spent hours unsuccessfully getting my old bike to stop throwing chains before spotting the wonkiness - the solid BB axle was actually bent somehow.

yes...i've come across solid axles that aren't straight,wonder if it's a manufacturing fault?or do they bend from wear?

 

[Profpointy]

m

yes...i've come across solid axles that aren't straight,wonder if it's a manufacturing fault?or do they bend from wear?

mine wasn't bent when I got it, but I was astonished that a 1/2" diameter steel bar had bent from my modest efforts - but it had. I guess it wasn't by any means the very best quality. Gave me an excuse to change to a triple - albeit underlying bike didn't really justify the cost. 15 speeds - wow !

 

[Karlt]

Heh. My commuting bike has an ancient set of Biospace chainrings (remember them?) because I had them handy when I put it together and I'm given to wonder whether the overshoots I get shifting to the big ring happen when the teeth happen to be furthest from the cage. Suffice it to say that if I adjust the limit screw sufficient to always avoid dropping the chain I then can't reliably get into the big ring at all. Either way, as you say, it's easy to put back using the shifter whilst in motion. Mine sometimes then locks up because the chain has come off the lower jockey wheel, but a quick back pedal and that's reset as well.