Using a chain stretch gauge
 

I got a Park chain gauge and have a question. Is the intended to be used with the chain under tension? If I just grab the chain and try the gauge using a reasonable amount of hand-force it won't go in. However, if I lock the brake and put weight on the pedal the gauge will pop in. Which way do you wrenches use this thing?

Thanks!

They are meant to be used with the chain on the bike at it's lowest stress - small front/small back cog. Push the black meniscus all the way away from you on the left. Insert the right end metal-peg into a inner link (thinner link) and the left hand peg (the one under the black meniscus) into an outer link (thicker link). It's supposed to be a tight fit. Push the meniscus back toward you until it stops, and take your reading.

Hand tension or the tension applied to the lower section of chain, while it's on the bike is enough.

FWIW, all of those chain checker tools are pretty much worthless. They don't check elongation or roller wear properly. If you really want to measure elongation, use a precision 12" scale. If you want to measure roller wear, use calipers.

Quite often a chain checker will show a chain to be .25% elongated when new. What it's measuring is the difference in the distance between rollers, which varies between brands.

Exactly - every new SRAM or Shimano chain I've checked with these toys has been 25% on the way to the grave. A good precision ruler and a digital-caliper* are what you truly need. Though the Part CC-2 can provide one with amusement.

* don't buy these from Park or other venues that advertise a stated purpose, like bicycles. You can find these on the net for under $15 if you buy from a distributor that doesn't brand it for bicycles, etc. Once it has someone's brand-name, the price doubles & triples. Same animal for under $15 as Park wants $35 for.

Thanks for the response; but I'm a little confused by the reference to the "black meniscus". This is the tool I have: http://www.parktool.com/products/det...at=5&item=CC-3

Gee, the park website even has a video. Still can't figure out how to use the tool?

Duh. But neither the video (which has no audio) or the written instructions say anything about how much tension the chain should be under during testing. Hence, my post.

Geeze - I've never used/played with the CC-3. Sorry...

Most people that take the effort to actually care about their chain will have the rear wheel off their bike often enough to just use a tape measure and measure a 24" section.
You get 2X the "resolution" than 12"!
If you really want to get "into it", rotate the chain aroun another 18-19" and measure again and repeat 1 more time. Compare measurements to see if there are any "trouble" sections.
For better accuracy, don't use the end of the tape measure. Use the 1 & 25" marks. The metal "thingy" can get bent or may not be located properly on a cheap tape measure. Besides, it's hard to "place" accurately.