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Change Chain?

509 Views 5 Replies 6 Participants Last post by BugMan, Apr 23, 2006

daniell

Discussion Starter · Apr 22, 2006

My present SRAM chain has more than 6000 miles on it. I just measured it. There is no apparent stretch. The remainder of my drivetrain is Ultegra. What should I go by, miles, or measurement?

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measuring accurately???

Just how are you taking this measurement? Although it;s certainly possible to have very little elongation after 6000 miles, it's not possible to have none.

I have a campy 10 chain with about 6000 miles on it that has so little elongation that the only way to accurately measure it is by comparing to a brand new chain, carefully stretched out and compared over 4 feet. Over this length I get about 1/16 inch or only 1/64 of an inch per foot.

First, clean the chain. Lay the chain on a bench, on its side and pull it tight. Place an accurate 12” scale on the edge of a pin. I use a precision machinist's scale. The pin at the opposite end will be totally covered when the chain is new. As the chain wears, this pins will begin to “peak out” from under the scale. Change the chain before ½ of this pin is exposed. The maximum allowable wear is 1/16” (.063 inch) per foot. One half of a pin is slightly more (.070 inch).

This measurement can also be done on the bike, holding the scale along the lower section of chain, but it’s a bit tougher to do.

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the Inbred

· #3 · Apr 22, 2006

purchase a chain checker...

Park has 2 versions, and Rohloff makes a nice one.

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Mersault

· #4 · Apr 22, 2006

Another measurement method that I do is while the chain is on the bike and using a stiff metal yardstick graduated to 1/16''. I put the chain on the small chainring and one of the middle cogs. Then lay the edge of the ruler on the chain and let is sit on top (it sticks way out in both directions, and that stabilizes the stick I also use the middle of stick for the actual measurement). I then push down on the crank to tension the chain (the bike is on the ground leaning on something so the wheel doesn't move), then I line up one pin and check how far the pin at 12" is, like C-40 said above. I just checked mine and it has 4000-4500 miles or so and I'd say it's at 1/32". It is past 12 inches, but has not gotten to the 1/16” point. I'll probably change it in a week or two, or when I get around to it. I usually change them about this mark anyway. Maybe I could get more mileage out of it, I just haven’t tried.

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Kerry Irons

· #5 · Apr 23, 2006

Nope

the Inbred said:
purchase a chain checker...Park has 2 versions, and Rohloff makes a nice one.

Chain checkers are generally expensive replacements for a ruler, except that they don't work as well. Some chains will show "nearly worn out" right out of the box, and the chain checker is trying to extrapolate elongation from only 1/2 inch of chain length. IMO they are a poor second choice to a ruler.

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BugMan

· #6 · Apr 23, 2006 (Edited)

Go by wear, not miles. A 12-inch accurately-cut steel ruler is plenty accurate. Measure as described by C-40. If no elongation, keep using it.

I've got 4,500 miles on a DA chain right now that is still not showing elongation - just checked it today. I keep it clean & lubed (Pro-Link/homebrew fan), dry, and don't do much mashing on it.

People who say chains must be replaced after 3K miles are 1) just repeating something they heard/read and don't really know, 2) don't maintain them very well, or 3) mash the he!! out of 'em.

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