Originally Posted by
stephr1
Seems to me that there might be more than .5% visual error in trying to use a ruler (even a steel one). Movement, visual angle, etc. would affect the reading. How do you do it and still ensure accuracy?
I have a caliper that can give me fairly accurate readings but even that can be problematic (like how to get 2 appropriately relative points to measure....like the same position on the 2 links used for measurement).
Get a precision 12 machinist rule. Place the end of the rule at the edge of a pin. The pin at the other end will be totally covered when the chain is new. When the covered pin is half exposed, you're just a little over .5%, or 1/16" of elongation. That's easy to see and plenty accurate. I suspect that many people prematurely toss chains, in attempt to avoid new-chain skip. If several chains are used in a rotation, you'll never get new-chain skip and each chain can be used longer.
When Wipperman does a chain wear test, they run them all the way to 1% elongation and the best chains do last far longer than the cheap ones. Only Wipperman's very best chain can beat a Campy chain. In my real-world tests, I've used a full length measuring fixture and never got a Campy chain to reach even .5% elongation before the roller wear and side wear were far too great to continue using the chain. That took 350 hours or 6,000 miles to reach that point. Roller wear is 20-30 times greater than the wear that creates elongation. The original space between the roller is about .205 inch. After 6000 miles, it was about .235 inch. For that reason I use a 6mm wide plug gage to drop between the rollers. If it ever goes through, the chain is really trashed.