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When is a chain kaput?(4 posts)

When is a chain kaput?Saddle_Sore
Jan 5, 2004 7:36 AM
Are there any obvious signs that a chain has "had it" - apart from things like it snapping? I have had a chain on my bike for about 6 years now and was wondering whether it needed replacing?
Measure chain wear.TWD
Jan 5, 2004 7:58 AM
You need to measure chain wear to tell if your chain's time is up. Park tool makes a ruler to measure chain wear, or you can simply use a ruler (which is tougher to use bot do-able). Chains wear over time causing them to elongate. This elongation comes from wear on the pins and rollers. Some people call this "stretch", but they don't actually stretch.

You need to measure how much wear has occurred on your chain. Each full link should measure 1" long. 12 full links should measure 1 foot on a new chain, measuring from the center of the first pin to the center of the pin on the 12th link.

Typically, the recommendation goes that you should replace your chain when you see 1/16" of elongation over 1 foot (12 links) of chain. If you let it get past that (to 1/8") you're looking at needing to replace your chain, cassette, and potentially chainrings too.

Letting the chain wear too far will cause excess wear and damage to your cassette and chainrings. If you try putting a new chain on excessively worn cassette or chainrings they will tend to skip around quite a bit, and will be unusable.

If you've gone 6 years without replacing your chain, I'm guessing you're going to need to replace everything (chain, rings, cassette, derailluer pulleys)if you've done any significant amount of riding in that time.

The amount of milage you get out of a chain varies alot depending on conditions. It takes a long time for me to wear a chain on my road bike, which almost never gets ridden in the wet and grit.

I go through several chains in a season on both my cross bike and mountain bike, since they get ridden a lot in nasty conditions (Oregon).
re: When is a chain kaput?Tiger Lilly
Jan 5, 2004 7:59 AM
Unless you don't ride much, 6 years is a very long time on a chain.

Get a ruler and put zero on the leading edge of a rivet. On a new chain, the leading edge of another rivet will fall right at 12". If the leading edge of that rivet reaches 12 1/16", replace the chain. If it gets to 12 1/8", you need to check you chainrings for wear. If your much over that, you may need to replace the whole drivetrain, as it will be worn to the point of not meshing with a new chain.

As a chain wears, it gets longer, and the pitch increases. When the chain pitch no longer matches the pitch (spacing) of the chainring or cassette teeth, it will start to wear them away at a faster than normal rate. The chain is steel and chainrings are usually Al, so they wear pretty fast. If they're hooked and look like shark teeth, they're dead. Cassettes are usually steel, but will also wear with the same "shark tooth" appearance.

Kathy
measure stretchgf99
Jan 5, 2004 8:00 AM
Most chain manufacturers recommend replacement when there is 0.75% to 1.00% stretch. Tools to do this are widely available and cheap, or any shop can do it for you.

After six years, you most likely need to replace it.

http://www.parktool.com/tools/CC_3BIG.shtml