Dura Ace - chain jumping on the 17.....irritating and dangerous any ideas?

Discussion in 'Cycling Equipment' started by BullGod, Mar 16, 2007.

  1. BullGod

    BullGod New Member

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    I have dura ace on my Trek race bike - the bike has done around 14,000km.

    I have noticed recently that there is a weird "grinding" sound from time to time when I am riding, especially when the right pedal goes from 12 - 2 o' clock.

    Of more concern is that if I accelerate whilst on the 17, the chain seems to either jump or slip, or maybe it goes in and out of gear, and there is a kind of "crunch" where I pedal hard, and make a half turn without any resistance.....in the best of circumstances this causes me to lose speed, in the worst of circumstances causes me to bang my knee on the bars and get the "nearly went over the handlebars" palpitations....

    Being able to jump hard on the 17 is something I need to do about 100 time every time I race, so things are not looking good.

    Does anyone have any idea of what might be wrong? I am hoping it is just something I can adjust, rather than the chain being stretched or the 17 being worn down.
     
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  2. capwater

    capwater New Member

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    You think just because it's DA it'll last forever??!!

    14,000km on the chain is quite a bit. Most likely it is stretched/worn and because it may be VERY worn it has chewed up your cogs. The 17 is one that gets a lot of action. Also look at your chainrings for a shark's fin appearance indicating they are worn. Chains are cheap, change them at the right time and you won't trash the rest of your drivetrain. Use a chain checker or a steel ruler to verify.
     
  3. BullGod

    BullGod New Member

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    yep more sharks fins than the JAWS movies - just took it to the shop.....new chain and drive train required.

    Cost - 160 odd euros
    lesson learned - change chain every few months.
     
  4. benkoostra

    benkoostra New Member

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    I replace my chain after about 2000 miles. It's amazing your xhain didn't snap after 14000.
     
  5. dhk2

    dhk2 Active Member

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    Changing the chain every few months would be a waste of money; they often last for 5000 km or more. Best way is to measure the "stretch" every month or so with either a steel ruler or a gauge. Parktool makes a "chainchecker" gauge (CC-3) which is very easy to use. When it drops into the chain, it's time to replace.

    Found my DA 9 sp cassette was worn after 16000 km, when I put on the second chain. My LBS predicted it would skip when I installed the new chain. When I came back the next day for the new cassette they weren't surprised....told me 16000 km was good life for the cassette.
     
  6. p38lightning

    p38lightning New Member

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    This is copied from Sheldon Brown's Website. See his drivetain article from which this is taken for more comprehensive info.

    Measuring Chain Wear

    The standard way to measure chain wear is with a ruler or steel tape measure. This can be done without removing the chain from the bicycle. The normal technique is to measure a one-foot length, placing an inch mark of the ruler exactly in the middle of one rivet, then looking at the corresponding rivet 12 complete links away. On a new, unworn chain, this rivet will also line up exactly with an inch mark. With a worn chain, the rivet will be past the inch mark.

    This gives a direct measurement of the wear to the chain, and an indirect measurement of the wear to the sprockets:

    • If the rivet is less than 1/16" past the mark, all is well.
    • If the rivet is 1/16" past the mark, you should replace the chain, but the sprockets are probably undamaged.
    • If the rivet is 1/8" past the mark, you have left it too long, and the sprockets (at least the favorite ones) will be too badly worn. If you replace a chain at the 1/8" point, without replacing the sprockets, it may run OK and not skip, but the worn sprockets will cause the new chain to wear much faster than it should, until it catches up with the wear state of the sprockets.
    • If the rivet is past the 1/8" mark, a new chain will almost certainly skip on the worn sprockets, especially the smaller ones.
    Chain Length
     
  7. bikeguy

    bikeguy New Member

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    14000 km is a long time for a drivetrain to last, that's pretty good going. I have a Bianchi that has 10k on it and the chainring seems fine, the cog I changed because I wanted a 12 final instead of 13. My LBS suggested changing the chain at 5000 km. A way to reduce chain wear is to run higher rpms, reducing forces on cog and chainring. Regular cleaning and oiling will also prolong the drivetrain life. I just spent 1.5 hrs yesterday cleaning the frame, chainring, chain and cog and derailleur of 1 bike. There was so much gunk that it felt considerably easier to ride today after getting it out.

    -bikeguy
     
  8. artemidorus

    artemidorus New Member

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    No point replacing a chain until it is worn. There's no substitute for checking "stretch". I use the Park CC-3 as well, it is a great piece of kit - none of that dreadful mucking around with rules.
     
  9. thomas_cho

    thomas_cho New Member

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    I just ordered the parktools chain wear tool.

    So what do you guys do with the worn chain? Throw it away?
     
  10. artemidorus

    artemidorus New Member

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    Yep. (Unless you haven't already got a chain whip...)
     
  11. matagi

    matagi Well-Known Member

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    Well, you could do this look closely at the "jewellery" on the guy on the right. :p
     
  12. thomas_cho

    thomas_cho New Member

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    Haha, I am not into that look.

    With a connex chain connector, or any connector, does that have to go as well with a chain change?
     
  13. matagi

    matagi Well-Known Member

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    Well it is part of the chain and subject to the same wear as the other links, so the answer is yes.
     
  14. artemidorus

    artemidorus New Member

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    Probably should, but last chain change I didn't bother.
     
  15. ROCYC

    ROCYC New Member

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    I had the same problem on a new bike I bought. The chain lengths were spreading apart under preasure. A new chain fixed the problem.
     
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