Bicycle Mechanics - Measuring a chain for chain stretch

OK, I'll admit it, I am a chain checker guy, but I am trying to remember the formula for measuring the chain with a ruler to tell if it is worn out. How many links to measure, and what value is good, and when it should be replaced. Thanks.

The normal recommendation is to accurately measure the distance between 24 pins (technically 12 full links) which should be exactly 12.0" for a new chain. If the distance has increased to 12-1/16" (0.5% elongation) the chain is marginal and should be replaced if you are planning to use the same cassette/freewheel with the new chain. If the chain measures 12-1/8" (1% "stretch) replace the cassette/freewheel along with it.

Thanks, That was what I was looking for.

Check this (http://www.nashbar.com/profile.cfm?category=99&subcategory=1234&brand=&sku=17012&storetype=&estoreid=&pagename=Shop%20by%20Subcat%3A%20Cassette%2FChain%2FFreewheel) out, it's only $4.95. It would be less with a Nashbar coupon....

check different sections of the chain too. chains don't strecth uniformly, they tend to stretch in just one area of the change.

I have one of those chain checkers and I don't like it.
As Hillrider says, if the chain is 0.5% elongated, it should be changed if you want to use the same chainrings and cassette with the new chain. The Nashbar and Park chain checkers won't register less than .75% elongation, at which point you could very well need to replace the cassette and chainrings also.

I just changed a chain that had not worn enough to register on the Park chain checker, but it was worn enough that the other parts needed changing.

I just changed a chain that had not worn enough to register on the Park chain checker, but it was worn enough that the other parts needed changing.

RoadBikeRider's (a weekly e-magazine) technical guru had an article on "chain checkers" today. His conclusion was that the Park version isn't sensitive enough to give good numbers until way too late.

My recommendation is that a good ruler is cheaper and more accurate than any of the chain checker tools.

RoadBikeRider's (a weekly e-magazine) technical guru had an article on "chain checkers" today. His conclusion was that the Park version isn't sensitive enough to give good numbers until way too late.

My recommendation is that a good ruler is cheaper and more accurate than any of the chain checker tools.

+1. Get a good 12" quality metal ruler and use it often. It's easy, and one of the few times a non-metric tool is appropriate for a modern bicycle.

RoadBikeRider's (a weekly e-magazine) technical guru had an article on "chain checkers" today. His conclusion was that the Park version isn't sensitive enough to give good numbers until way too late.

My recommendation is that a good ruler is cheaper and more accurate than any of the chain checker tools.

+1. That's good to know, that a tech guru came to the same conclusion. Remember the thread about three weeks ago that reached at least three pages, in which we examined all the minutiae as to why the ruler is more reliable? That pretty much clinched it for me! The ruler is the only tool that measures *only* the pitch of the chain, which is the only measurement that counts.

+1. Get a good 12" quality metal ruler and use it often. It's easy, and one of the few times a non-metric tool is appropriate for a modern bicycle.
Better to get a ruler longer than 12" if you're going to be measuring distances longer than 12". Eh, wot? ;)

I often have a spare, unused chain handy which I use to check wear on a used chain. Hang both chains on a nail and pull them tight. You can easily see 3/16" wear over 3' of chain.