Originally Posted by
HillRider
I'd be very suspicious of either chain checker as many are highly unreliable. I can't imagine anyone wearing out any chain in 500 miles unless you weigh 350 pounds and do nothing but climb hills.
Use a good ruler, preferably a metal one, and measure a nominal 12" (24 pins) of your chain. Measure the lower run which is under slight tension from the rear derailleur's spring.
A new chain should measure nearly exactly 12.0" over 24 pins. A chain that's slightly worn but usable will measure 12-1/16" between the centers of the pins and a worn chain that definitely needs replacement will measure 12-1/8". Some riders who want to protect their cassettes will replace a chain at 12-1/16".
I've heard this debate before, and I have a third opinion to offer. Think it through yourself, then take it for what its worth.
In my opinion, you need to check both ways (chain checker
and ruler). Why? They measure different things, and therefore may detect different problems.
- The "ruler method", by measuring wear that increases chain length, detects wear between the pins and the side plates, but won't tell you anything about the state of the rollers.
- The "chain checker" method detects wear between the rollers and the pins, and external wear on the roller. It might pick up on side-plate-to-pin wear, but it won't be as sensitive becasue it measures fewer "side-plate-to-pin" interfaces.
I've seen chains that passed the ruler method, but had floppy rollers, or had rollers that were worn ever-so-slightly concave by the sprockets.
I do 'em both. If it fails either test, I replace it. Chains are cheaper than casettes.