When I am shifting into the highest gears, sometimes the chain gets lodged between. What can I do to remedy this situation?

Steve Jones's Answer.

	Steve Jones The author of four mountain-biking books, Steve Jones has logged thousands of miles of trails and backroads. Meet Steve Answer Archive Biking Forums

There are several reasons why you may be having trouble getting into the highest gear and staying there. The most common reason comes from having a maladjusted derailleur. It sounds bad, but it's relatively easy to fix.

First, put your chain back on the smallest rear cog (the highest gear). If the chain has been violently wedged in between the outer section of the cog and the chain stay (the lowermost part of the frame that runs parallel to the ground), you may need to pry the chain free with a screwdriver. Otherwise, you can lift the chain up and back with your hand, using a rag to keep your hand clean.

If the chain has been coming off only occasionally (as opposed to every time you shift into the highest gear), the misalignment may only be slight. However, you still should be able to detect it with your eye.

Now locate the adjustment screws located on the derailleur. They should be facing the back and marked with an"L" and an "H." Take a small screwdriver and begin adjusting the screw located nearest the "H" and turning it counterclockwise a half-turn at a time. This should move the jockey wheel closer to the bike. If you have a rack where you can place your bike's back wheel off the ground and turn the pedals, test the alignment by cranking the pedals. If the jockey wheel went to the outside instead of the inside, turn the adjustment screw the opposite way — but only a half-turn at a time. When you're satisfied with the alignment, the problem should be fixed.

Another reason why you may be having the chain come off: you are shifting incorrectly. Make sure you don't have the chain ride on the largest front chain ring while the chain rides on the smallest rear cog. This arrangement puts the chain travel out of parallel to the bike frame, putting stress on the teeth of the ring and cog. The solution is to shift onto the middle chain ring.

Finally, it is possible the chain has been stretched, especially if it is new. Remove a chain link, but only as a last resort.