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Discussion Starter · #1 ·
OK, here is my problem. I am more of a mountain biker, but bought myself a second-hand 2003 cannondale R700 a few weeks ago to do a bit of road riding during the muddy winter here in the UK. I have only been out on it a few of times and everything was fine, but the chain started skipping this weekend. First of all it was just skipping on the the second highest sprocket down to the third, but was fine everywhere else. I have a lot of experience with MTBs, so I checked that the cables weren't sticking and adjusted the cable tension. Also made sure that the cable was seated properly at the point where it clamps on to the derailleur. I thought that maybe the rear mech hanger could have been bent slightly, so I gave it a tug and it looks straight to me and adjusted the cable slightly. Now it is skipping at the bottom end of the cassette (the small sprockets), but not at the top end! It has 9-speed 105 components and they really don't seem to have much wear on them. Any suggestions??

Shame about Pantani!!
 

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The Edge
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You sound to have a classic case of chain stretch with a worn cassette. The chain the the cassette wear together on the most used cogs, that's why some of the cogs (usually close to each other) shift fine with the chain and the others (like the lower tooth count cogs usually) don't. My advice would be to get a second opinion at a shop where they can quantify your chain stretch and give you a hard fast answer on whether you'll need a new chain or a new chain and cassette. All in all, after 45 bucks you're bike will shift like magic again.
 

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Discussion Starter · #3 ·
Thanks for your help, I'll measure the chain tonight and see how stretched it is. I can compare it to the chain on my MTB which is virtually brand-new. Because the bike is second-hand I don't know how many miles it has done. Will i need new rings on the front if I replace the chain and the cassette?

Thanks,

Steve
 

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A wheelist
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smolenice said:
Thanks for your help, I'll measure the chain tonight and see how stretched it is. I can compare it to the chain on my MTB which is virtually brand-new. Because the bike is second-hand I don't know how many miles it has done. Will i need new rings on the front if I replace the chain and the cassette?

Thanks,

Steve
Steve, try reading the info on chain wear and its measurement in my FAQ -


http://www.execulink.com/~dtierney/wmc/faq.htm
 

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don't agree...

Classic chain skipping usually occurs only on the most heavily used 1 or 2 cogs, right after a new chain is installed on a old cassette. A readjustment of the derailleur would not move the skipping from one cog to another.

Chain stretch is best measured with a tool meant for the job like a Park chain checker or a 12-inch machinist's scale. A ruler will do in a pinch, but it's not as accurate. Stretch the chain tight and lay the scale on the chain with the left end at the very edge of a pin. The pin on the right end of the scale will be completely covered by the scale when the chain is new. As the chain wears, the pin on the right side will begin to peak out from under the end of the scale. When 1/2 of the pin on the right side is visible, the chain should be replaced.
 

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Discussion Starter · #6 ·
Maybe I wasn't too clear with my explanation. The chain was jumping down to the 3rd sprocket from the second, but was changing ok in every other gear. This was what made me suspect that maybe the derailleur hanger was bent. Then after i tried bending the derailleur i was getting the jumping at the lower end of the casette, which made me think that the cable might be a bit sticky.

Hmmmm......

Will check chain length anyway. Quite fancy an excuse to buy a new cassette (12-27) and chain anyway, that 39-25 low ratio combination is a killer when you are used to a 22-32 ratio on an MTB
 

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A few possibilities.
1) Stiff link
2)Derailleur adjustment
3) Worn chain or cogs.
 

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Chili hed & old bike fixr
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After you do any "precision bending" on the frame or components without gauges you should take it to the LBS to get the bent parts put where they are supposed to be. You should have completely reset the derailleur limits and cable tension after your adjustments, if nothing else. It is no appropriate to start yanking on things and bending whatever, if you have no idea what the results will be. You can bend things that were not wrong when you started, which may cost more than the trip to the LBS for the original problem.
 

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The Edge
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I feel the same. I forgot to mention that chain tension also affect shifting. Make sure your b-screw is calibrated.
 
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