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New Chains
I've been told it's essential to replace chain and sprokets at the same time
What happens if you fit a new chain to old sprockets? Ken .. |
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#2
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New Chains
Ken wrote:
I've been told it's essential to replace chain and sprokets at the same time What happens if you fit a new chain to old sprockets? A new chain will work fine on old sprockets as long as sprocket wear isn't excessive. If the sprocket teeth have developed a wear pocket (not always visible to the eye), then the new chain will periodically skip forward by one tooth under load. Replacing chains when wear reaches 0.1mm elogation per link will mean that sprockets last a long time (many chains). John |
#3
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New Chains
Depends how worn the old chain was. Hang the old chain up and use a good
steel rule to measure how long 24 links are. If they have worn to measure 12-1/8" or more, then I would replace both chain and cassette, as the new chain and old cassette won't mesh well together. 1/8" is approximately 1% wear. "Ken" wrote in message ... I've been told it's essential to replace chain and sprokets at the same time What happens if you fit a new chain to old sprockets? Ken . |
#4
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New Chains
John Henderson wrote:
Ken wrote: I've been told it's essential to replace chain and sprokets at the same time What happens if you fit a new chain to old sprockets? A new chain will work fine on old sprockets as long as sprocket wear isn't excessive. If the sprocket teeth have developed a wear pocket (not always visible to the eye), then the new chain will periodically skip forward by one tooth under load. Replacing chains when wear reaches 0.1mm elogation per link How do you test this? Steve = : ^ ) |
#5
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New Chains
Steve Ball wrote:
John Henderson wrote: Replacing chains when wear reaches 0.1mm elogation per link How do you test this? Like Nick says, 24 links at 1/2" each should measure 12". Measured with a good ruler, 1/8" elongation over 12" is the wear limit. I cheat and use a Rohloff chain checker: http://www.rohloff.de/en/products/caliber_2/index.html I prefer using this to a ruler. Park Tools also makes a version: http://www.parktool.com/products/det...=5&item=CC%2D3 Because a badly worn chain doesn't distribute the load over multiple sprocket teeth, it causes rapid sprocket wear. John |
#6
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New Chains
John Henderson wrote:
Steve Ball wrote: John Henderson wrote: Replacing chains when wear reaches 0.1mm elogation per link How do you test this? Like Nick says, 24 links at 1/2" each should measure 12". Measured with a good ruler, 1/8" elongation over 12" is the wear limit. I cheat and use a Rohloff chain checker: http://www.rohloff.de/en/products/caliber_2/index.html I prefer using this to a ruler. Park Tools also makes a version: http://www.parktool.com/products/det...=5&item=CC%2D3 Because a badly worn chain doesn't distribute the load over multiple sprocket teeth, it causes rapid sprocket wear. John I've got a Park Chain check tool that checks for 0.75% and 1% wear. I usually replace my chain before it gets to 0.75% - chains are cheap compared to cassettes. My test now is as follows: Get out a set of vernier calipers Set distance between tines to 132mm Insert tines into chain links. Extend calipers If distance is greater than 132.6mm, replace chain This represents about 0.5% stretch. Note, this method comes from the Campagnolo instructions for their 10sp chain. Since all bicycle chains have the same pitch, it works on all chains. DeF -- e-mail: d.farrow@your finger.murdoch.edu.au To reply, you'll have to remove your finger. |
#7
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New Chains
Ken wrote:
I've been told it's essential to replace chain and sprokets at the same time What happens if you fit a new chain to old sprockets? I've found an ASCII diagram I once did to help show why a new chain skips on a worn sprocket. View with a fixed (not proportional) font for this to make proper sense. \ / | | | | | \ | | | / \___/ /|\ /|\ | | N W "N" represents the line taken by the bushing on a new chain trying to mesh with a worn sprocket tooth as it's fed onto it. And "W" represents the line of the corresponding part on a worn chain. We're looking at a tooth on the bottom of the sprocket, rotating clockwise (ie, towards the left). The reason the new chain link is committed to line "N" is that it's sitting in the pockets of the teeth it's already engaged with (having been pulled into those pockets by peddling pressure). And it doesn't have enough "stretch" to allow it to move over and follow line "W" into the gap between teeth. So every now and then, the chain rides up over the top of a tooth all the way from meeting the sprocket at the bottom to leaving it at the top. That the hook (the unworn material towards the head of the tooth) is the problem can be demonstrated by removing it (on all teeth of that sprocket) with a grinder. The skipping disappears. But this is only a temporary repair, as the case-hardening is gone. John |
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