Guided and Self-Guided
Mountain Biking and Walking Holidays
Gears slipping under pressure.
One of the most frustrating problems that can occur on a bike is "chain slip" You are pedaling along happily and come to an incline, as you start to apply more pressure to the pedals, clunk - your foot slips forward an inch or two as the chain slips off a cog tooth. The problem normally is related to wear somewhere in the drivetrain. But check the simplest things first. Look for:-
Sticky shift cable. If the cable is not releasing cleanly there can be a clunk and slip as it finally allows the gears to change.
Loose jockey wheels. The movement in a lose wheel can be enough to allow a chain to wander from side to side and attempt to ride up or down a gear. If it's loose, tighten it.
Bent derailleur hanger. Look from the back of the bike. The derailleur hanger should hang down vertically from the bottom of the cassette. If it is bending in towards the wheel or out away from the bike then it is bent. If it is bent it may try to pull the chain in the direction of the bend causing the gears to auto-change and slip.
Worn derailleur pivots. If there is laxity in the joint of the derailleur it will wobble. If it does then it can pull the chain out of line and cause a gear slip or unwanted gear change
Stiff Link. If a link is stiff it can ride up over a cog and fall off. Watch the chain as it passes over the rear cassette and see if you can see a link which does not glide snuggly over the cog. If it is stiff, work on it, free it up.
Rusted and Stiff chain. If the bike has been sitting for some while look to see if the chain is rusted and therefore less flexible. Clean it up and lube it and try riding again.
Worn and stretched chain. To make life easy buy yourself a chain stretch indicator. This is a simple device which fits into the chain and tells you if it has stretched beyond efficient use. Alternatively measure it. A new or good chain will measure exactly ½" for every chain pin. If it is stretched change it.
Worn cogs. Check out the chain ring and cassette teeth, if they look hooked or like a shark fin then it is time for a replacement chain ring or cassette.
Drivechain management. Every time you use your bike there is some wear to the teeth of the gears and to the chain itself. Frequent lubrication will extend the life of the components. Parts manufacturers suggest frequent chain changes on a bike because a worn stretched chain will wear out other components more quickly. An alternative view is run everything together for as long as you can and then to change the entire drivechain in one hit. Yes it is expensive but you may have changed your chain 5 or 6 times on the other method.
BIG CAUTION. If you have badly worn component in the drive chain, change everything. If you try mixing new and even mildly worn components you may get chain slip but will certainly wear out the newer components more quickly.
12th July 2010
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