My chain keeps falling off!

[jeepinjakear15]

I have a western flyer and I put redline chain tensioners on it the chain has a little slack but not much. It's not too tight I don't think either. When I peddle hard like up a hill the chain falls off! Any ideas its a single speed bike.


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[longshort]

try to check the alignment of tensioner and sprockets , with a straight edge, see everything is line up with each other. does it feel like it has flex to the bicycle for any reason ? hope this helps.

 

[TheFlyingDingo]

Check alignment, and then check if the teeth on the sprocket are worn. I had this problem with my Predator, many many years ago.

 

[ozzmonaut]

Check that the bearing cups in the crank hanger are seated properly. If one or both are slightly unseated, it will cause the crank/sprocket assembly to turn unevenly. The chain will go on and be fine when not under too much pressure. But at the top of that revolution where the sprocket teeth are too far in or out, combined with more tension from pushing uphill, it can be enough to make the chain jump.

 

[Outlaw90]

your front sprocket could be bent a little bit too...

 

[Wildcat]

If the sprocket is bent, you can gently straighten it. Put the bike on it's handlebars and seat and take the chain off the sprocket. Check for play in the crank bearings and adjust them, might need some lube on the bearings. Spin the sprocket and watch the alignment next to the chainstays. Take a mallet or hammer and tap gently to straighten it. I've also used a crescent wrench with the jaws adjusted to slide over and bend the sprocket. the key is to be very careful and do just a little at a time. You can check the alignment of the chain and see if it's right. An washer on the rear wheel can give a slight adjustment if you need to.

Frame flex may be the reason also. When you pump uphill, the cranks may twist the frame with the torque you are putting on them, making the sprocket go slightly out of line with the chain.