daven1986

Hi all,

I bought a chain wear indicator tool https://www.chainreactioncycles.com/M...?ModelID=10219 and it fits in my chain on the 0.75 side, however when I use a ruler the pins are exactly 12 inches apart. Do I have a dodgy tool?

Thanks

Daven

EDIT: this happens on both my bikes - 1 is hybrid, 1 is a road bike

Lawrence08648

I bought one from Performance and returned it, it showed my recently installed chain as worn, it showed a worn chain as worn, it showed a chain with 500 miles on it as worn, and it showed a brand new chain out of the box, never on the bike as worn.

daven1986

*sigh* that is really annoying! Can I instead just use the 1.0 marker as my limit?

DaveSSS 

These chain wear measuring devices are all flawed in design, since they apply pressure to a roller at each end of the measurement. Although the center to center distance is the same on all brands of new chains (measured at the pins), the roller may not be the same diameter, the hole in the rollers may not be the same diameter and the "shaft" formed into the inner plates may also not be the same. This often causes these tools to show a new chain to have .25% elongation, when it really has none. After some wear, even if you subtract this incorrect .25%, the tool combines roller wear with elongation, exaggerating the elongation. The roller wear can be as much as the elongation over the very short length that is being measured and the result is a report of more than twice the actual elongation.

A 12 inch precision machinist scale is the best thing to use for measuring elongation. Rather than trying to eyeball center to center on the pins, you lay the scale with the end at the edge of one pin. The pin at the opposite end will be completely covered when the chain is new. When the covered pin is exposed by nearly half it's diameter, you've reach .5% elongation.

Not all chains expire due to elongation. I've measured a Campy chain to have only .1-.15% elongation after 6,000 miles, but that did not mean it was not worn out. A caliper check of the roller spacing showed an increase from .200 inch to about .240 and feeler gages showed nearly double the original side clearance. Use a single chain on a cassette for that long and you're almost guaranteed to get chain skip on at least one cog, when a new chain is installed.

daven1986

well both chains have done around 1000 miles the hybrid one slightly more.

I think I shall use both methods, if it fits 1.0 then I will double check with the ruler.

thanks

DMF 

DaveSSS, interesting post. I knew that the little slip gauges aren't particularly accurate but you've highlighted why (not). Thanks.


daven, why use a flawed method if you have access to the real thing?

daven1986

because it is quick and easy, I don't mind using a ruler but I'd like some use for the tool I bought!!

HillRider

I've found the Park CC-3 chain checker agrees quite well with the 12" ruler measurement, at least for the Shimano and Wippermann chains I've used it on. When the ruler says 12-1/16" the CC-3 won't fit the 0.75% tab into the links. When the ruler just exceeds 12-1/16" the 0.75% tab is a firm fit. When the ruler says almost 12-1/8" the 0.75% tab also says "throw away the chain"

daven1986

I think I am going to calibrate my tool using the ruler to see when a chain is really worn. The tool is just so much quicker!

DMF 

Fwiw, mine (also Park?) isn't far off either. But I prefer to accept as little inaccuracy as I can get away with.

operator

I used to be a huge fan of that tool. Not so much in recent times. Some new chains measure near .5 on that tool. Which means any sort of wear = toss, according to the CC3. A 12" ruler on the chain never fails. Unless your eyesight sucks. Most of the bikes we see in, is either new from the cc3, or completely off the scale. The cc3 is useful for this situation.