Bicycle Mechanics - chain stretch?

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atomship47
07-18-07, 07:02 AM
my $6 peformance bikes chain wear gauge indicates my chain is not worn to the point of needing replacement.
however, my shifting/drive-train is acting squirrelly. the chain sometimes jumps off the chain rings when i shift up or down. also, shifting in to larger cogs in the middle of the cassette is strange. i have a hard time shifting just one cog. it usually doesn't shift at all or jumps 2 cogs.
i had a nbc at about 500 miles. does cable stretch occur throughout the life of your bike?
i'm suspecting my chain is too loose. should i try removing a link?
HillRider
07-18-07, 07:12 AM
All of this sounds more like the front derailleur limit screws and the cable tension at both ends need attention. 500 miles shouldn't wear out any chain unless you ride only in sand.
miamijim
07-18-07, 08:19 AM
When my bike was doing the same thing in the back I replaced both pulley wheels and all was good. As far as the front issue.....read the post above mine.
atomship47
07-18-07, 10:52 AM
All of this sounds more like the front derailleur limit screws and the cable tension at both ends need attention. 500 miles shouldn't wear out any chain unless you ride only in sand.
i should have been more clear....i had a nbc at about 500 miles. that was a couple of months ago. i've got about 1300 miles on it now.
...my shifting/drive-train is acting squirrelly. the chain sometimes jumps off the chain rings when i shift up or down. also, shifting in to larger cogs in the middle of the cassette is strange. i have a hard time shifting just one cog. it usually doesn't shift at all or jumps 2 cogs.
I was experiencing similar symptoms several weeks ago and the problem turned out to be a link that was binding and getting stuck. A stuck link is easy to fix, too.
Bobby Lex
07-19-07, 05:31 AM
my $6 peformance bikes chain wear gauge indicates my chain is not worn to the point of needing replacement.
You can double check the accuracy of your measuring tool with a common ruler. 12 chain links (pin-to-pin) should be exactly 12 inches. Less than 1/16" over that is acceptable. 1/16" to 1/8" is marginal. More than 1/8" is unacceptable and should be changed. It is unlikely that a chain with only 1800 miles on it needs to be replaced, but only careful measuring will confirm that.
however, my shifting/drive-train is acting squirrelly. the chain sometimes jumps off the chain rings when i shift up or down. also, shifting in to larger cogs in the middle of the cassette is strange. i have a hard time shifting just one cog. it usually doesn't shift at all or jumps 2 cogs.
Sounds like your cables need adjusting.
i had a nbc at about 500 miles. does cable stretch occur throughout the life of your bike?
Cable "stretch" is subject to debate. Some folks take the position that modern cables don't actually stretch so much as clamping bolts, cable housing, and ferrules settle-in, which affects shifting performance. Either way, it is not uncommon to have to tweak cable tension from time to time
i'm suspecting my chain is too loose. should i try removing a link?
Your derailleur spring takes up any slack in your chain, so removing a link wouldn't affect anything. Don't mess with removing links from your chain, unless it has stretched, in which case you would need to replace the chain, not remove links.
As usual, the Parktool website has great instructions for dialing-in shifting and for making cable adjustments.
http://www.parktool.com/repair/byregion.asp?catid=53
And Sheldon's site has some great information on chain stretch and drivetrain wear.
http://sheldonbrown.com/chains.html
Bob
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