Tuesday, December 7, 2010

The Times, They are a Chainin' (Part 1)

Now is the time to start getting your bike ready for next spring.  Most of the parts on your bike are maintenance free these days.  Cable housings have teflon lining, hub and bottom bracket bearings are sealed, and pedals don't need much attention.

However, the chain is the one part that is constantly exposed to the elements and has lots of moving parts.  A typical chain will have around 114 links, all of which have two sliding plates.  The chain has no bearings to reduce rolling friction, so these links are exposed to constant metal-to-metal wear.  Throw in some road grit and your chain will wear out.

How do you know if your chain is worn out?  There are some fancy tools you can use, but it can be done very easily with a ruler.  All bicycle chains have 24 links per foot, sometimes described as 1/2" pitch.  Take a ruler and measure the distance between the center of the pins for 24 links.  A new chain will be exactly 12 inches (24 x 1/2 = 12, right?).  A chain is in good shape until this distance becomes 12-1/16 inches.  Now is the time to order the new chain.  At 12-1/8", replace the chain.  Now.

If you continue to ride with a worn-out chain, the first casualty will be the cassette or freewheel cogs.  The stretched-out chain will not mesh exactly with the teeth and c

What kind of chain should you get?  Match the chain to your rear cassette.  If you have an eight-speed cassette, buy an eight-speed chain.  A nine-speed chain will generally work with an eight-speed cassette, but not the other way around.

Beware of the "fancy" chain, with exotic construction or materials.  These chains are high-priced with very little savings in weight and no increase in performance.  The SRAM PC-951 chain costs about $22 and weighs 300 grams.  The PC-991 hollow pin chain costs $62 and weighs 279 grams.  This is about 3/4 ounce or $853/pound.  If you're this concerned about weight savings, get a haircut, go without socks or gloves, get rid of the handlebar tape, don't take water, or any other number of weight savings ideas.

Up next: Replacing the Chain

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