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Correct way to measure chain wear?
Started to wonder about the correct way to measure chain wear. Option
1 is to buy a chain checker (e.g. Park CC-2). Option 2 is to measure... Conventional wisdom is to measure 12 links and if it is greater than 12.125", then the chain is worn and should be replaced. Fine. However, the chain really has three main places of wear: 1) Inner plate to pin 2) Inner surface of rollers to pin 3) Outer surface of rollers Now, measuring 12 links only takes into account wear mechanism (1). It could be that this is the major wear mechanism, as the loads are most concentrated being the smallest interface area. However, what the chainrings and cogs care about is the pitch of the chain as measured from outer surface of one roller to the next. So, if the rollers become worn so they are "thinner" than they originally were, the pitch of the chain could increase, even if we the inner plates do not wear. Question: 1) Are wear mechanisms (2) and (3) negligible? 2) Would it make more sense to measure 12 links from roller surface to roller surface (using calipers or something of the sort) instead of pin to pin? 3) If (2) is true, then does the Park CC-2 do the correct thing as it sits on top of the chain? |
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#2
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Correct way to measure chain wear?
Ken Nishimura wrote:
Started to wonder about the correct way to measure chain wear. Option 1 is to buy a chain checker (e.g. Park CC-2). Option 2 is to measure... Conventional wisdom is to measure 12 links and if it is greater than 12.125", then the chain is worn and should be replaced. Fine. However, the chain really has three main places of wear: 1) Inner plate to pin 2) Inner surface of rollers to pin 3) Outer surface of rollers Now, measuring 12 links only takes into account wear mechanism (1). It could be that this is the major wear mechanism, as the loads are most concentrated being the smallest interface area. However, what the chainrings and cogs care about is the pitch of the chain as measured from outer surface of one roller to the next. So, if the rollers become worn so they are "thinner" than they originally were, the pitch of the chain could increase, even if we the inner plates do not wear. Question: 1) Are wear mechanisms (2) and (3) negligible? 2) Would it make more sense to measure 12 links from roller surface to roller surface (using calipers or something of the sort) instead of pin to pin? 3) If (2) is true, then does the Park CC-2 do the correct thing as it sits on top of the chain? Measuring from any two consistent positions on the ouside of the chain will give almost identical results - you have to make the measurement with the chain under some tension. The most wear happens in the order 1-2-3. External measurement of the chain does take into account mechanism 2, as you describe it, if the chain is under tension. -- Jim Price http://www.jimprice.dsl.pipex.com Conscientious objection is hard work in an economic war. Aye!. |
#3
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Correct way to measure chain wear?
"Ken Nishimura" wrote in message ... Started to wonder about the correct way to measure chain wear. Option 1 is to buy a chain checker (e.g. Park CC-2). Option 2 is to measure... Conventional wisdom is to measure 12 links and if it is greater than 12.125", then the chain is worn and should be replaced. Fine. However, the chain really has three main places of wear: 1) Inner plate to pin 2) Inner surface of rollers to pin 3) Outer surface of rollers Now, measuring 12 links only takes into account wear mechanism (1). It could be that this is the major wear mechanism, as the loads are most concentrated being the smallest interface area. However, what the chainrings and cogs care about is the pitch of the chain as measured from outer surface of one roller to the next. So, if the rollers become worn so they are "thinner" than they originally were, the pitch of the chain could increase, even if we the inner plates do not wear. Question: 1) Are wear mechanisms (2) and (3) negligible? 2) Would it make more sense to measure 12 links from roller surface to roller surface (using calipers or something of the sort) instead of pin to pin? 3) If (2) is true, then does the Park CC-2 do the correct thing as it sits on top of the chain? You're over-analyzing this. The only thing that's important in chain wear is change of pitch. Wear of the pins and the diameter of the inner plates that bears on the pins are the only things that affect pitch, since the wear is cumulative with respect to change in chain length. Roller wear isn't cumulative. |
#4
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Correct way to measure chain wear?
In article , Ken Nishimura
writes: Conventional wisdom is to measure 12 links and if it is greater than 12.125", then the chain is worn and should be replaced. Fine. If it gets that far you will likely have to replace your cassette or freewheel too. Tom Gibb |
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