The article mentioned 0.75% elongation. I try to keep it at 1/16 inch in 12 inches, measured with a steel ruler. (It's kind of difficult to be accurate: you have to look straight at the ruler lines, measure against the edge of the pin, and hold the other end in place without moving.) 12 1/16 is 12.0625 inches, or .0625%.
Originally Posted by
studbike1
I agree with shimano in terms of the test having limited translation to the real world. Even if you increase the average speed to 12mph, most of these chains only lasted about 1000 miles, and everyone who rides a lot knows that a chain should last at least twice that long with minimal lubrication, and will go longer if you maintain it frequently.
Also it looks like the campy chain got something wrong towards the beginning of the test. the slope of the curve is similar to the winning connex chain.
They were doing the equivalent of a 150 pound rider only riding up an 8% grades at 8 mph, 90 rpm, with muddy water on the chain. 1000 miles would be reasonable!
Originally Posted by
DaveSSS
I suspect that the application of excessive abrasives reduces all chain lives significantly. If that had not been done, the testing might have taken 3-4 times as long. I wanted to test Jobst Brandt's contention that as long as a chain wasn't used beyond 1% elongation, the mating sprockets would not be damaged. I rode a Campy 10 chain for 6,000 miles or 350 hours and measured no more than .25% elongation over the full length. Although the elongation was small, rollers had a very large amount of wear, especially on the hole in the roller and the side clearance was twice that of a new chain. The two most used sprockets, my 19 and 21 both skipped with a new chain. That proved that with this chain elongation was irrelevant, compared to roller wear.
I recently checked a KMC x11.93 chain against my chorus 11 chains with similar mileage and found the KMC to have at least .3% elongation, while the campy chains were nearly like new.
The only difference between a record and chorus chain, that I know of is the hollow pins on the record model.
Yes, my Campagnolo 10 speed chains had extremely low elongation, even after 3500-4000 miles. But the chains seemed to have a lot more flex side-to-side. I didn't notice much cassette wear. I tended to replace the chain around 3500 miles before going on a biking vacation, just to not worry about riding an older chain out of town.
I wonder how the rollers can get this worn without showing much chain elongation.