Originally Posted by operator
Beh... a ruler does the exact same thing as the chain checker things.
...it is better to replace chains than cassettes -> they cost less to.
Agree with the second phrase, not with the first. I thought this too, that the ruler test does the same thing. NOT! Here's why. If the pins and side-plate bushing-shaped contact points are what's wearing, then yes, you'll be able to measure the wear with a ruler, because the chain will elongate overall from pin to pin.
BUT if the major wear is happening on the *
inside of the rollers*, then the length of space between the rollers will increase even though the distance from pin to pin won't change appreciably. That increased space between rollers will show up on a gauge, but not with a ruler, because the distance between pins hasn't changed much. A ruler can only measure the distance between pins. Not the length of the space between rollers! You need a gauge for that. I just found this out the hard way.