Chain malfunction

Old 10-06-04, 08:50 AM
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Chain malfunction

I'm hoping some Bike Expert type can help me with a problem. The gears in my friend's bike will all lock together and begin to turn at once, but not drive the chain. If she rolls the rear tire back, it will re-engage the chain, but it can repeat the problem at any time. Any help you can provide would be great. Thanks.

Frank Ivan
Old 10-06-04, 03:43 PM
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Um, not exactly sure what you are describing. When you say the gears lock together, do you mean the cluster of cogs on the rear wheel, or the chainrings up front? What is happening with the chain - is it not staying on the gears?

Rewinding a little, what kind of bike is this - is it a typical mountain bike, or a bike with a three speed hub in back? Assuming its a mountain bike, the way things work is that the chainring up front pulls the chain, which pulls the cogs in back, which turns the wheel.

Simple, but a few things can go wrong. If the derailleurs (the cage up front and doohickey in back which move the chain side to side) are out of adjustment, the chain will hop up and down between gears or may come off of the chainring or cogs alltogether. A bike shop can adjust these quickly and cheaply, or may install new cables if the old ones are dirty and brittle.

Second, the chainrings may be worn if they are really old. This results in something called chainsuck, where the chainrings won't let go of the chain and everything binds with a sickening *crunch*. Third, the cogs in back may be worn. In that case, the chain may skip as if it was out of adjustment.

Finally, the freehub (the part of the wheel that rear cogs slide onto) may be toast. In this case, you can pedal all day but the wheel doesn't move. Or conversly, you can pedal but you can't coast without the pedals turning (like your old tricycle!)

Any of these sound your problem?

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