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Another rookie question: n-speed chains

Discussion in 'Bicycle Mechanics' started by marc, Oct 30, 2008.

  1. marc

    marc Speeding Up

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    Another of those things that should be obvious and all the maintenance guides assume you already know, but that would be embarrassing and expensive to get wrong.

    Chains: the maintenance guide I've been reading keeps referring to "7-speed chains" "9-speed chains", etc. In the store, the boxes for chains are labeled the same way. This refers to the number of gears on the rear cassette, and not the total number of speeds, right?

    In other words, I have double crankset in front, and a 7-gear cassette in back, so I'd need a 7-speed chain, right?

    I think what confused me is that I see 10-speed chains, but I don't recall ever seeing 10-gear cassettes.

    Thanks.
  2. Philip

    Philip Speeding Up

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    Hi Sublight,

    Not a silly question :)

    A while a ago a 7-cog (gear) cassette was standard. Over time the manufacturers have managed to increase the number of rear cogs. The standard today is 10. This year Campagnolo move to 11. To accommodate the additional cogs the manufacturers have made the space between the cogs narrower. Therefore, you need a 7-speed chain for 7 cogs. 8 for 8, 9 for 9 and 10 for 10 to match the width of the chain to the gap between the cogs :)

    Philip
  3. marc

    marc Speeding Up

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    Wow, fast answer. Thanks!
  4. WhiteGiant

    WhiteGiant Maximum Pace

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    Exactly!

    10-speed cassettes came out about a year or 2 ago (making a total of 20 for two front chain-rings).
    Still, 2x9 is probably the most common (for those of us with the lack of funds to upgrade). 2x7 is a little earlier, but still decent. And I've also seen a lot of 3x8 as well.

    ie. If you have 7 gears in your rear-cassette, you'll need to buy a "7" chain!

    The main difference is with the spacing between each cog - To fit seven cogs into a 60-something millimeter space allows for a wider chain. When there are nine cogs at the back, the chain has to be narrower. And even more narrow for a 10-speed cassette.
    The other difference is the stretch that the rear derailleur will allow for - I think having "seven" at the back means your chain can be shorter; and ten at the back means the chain will be slightly longer (I'm only guessing on this, so please confirm with other sources - AlanW is the man to ask regarding the finer points of chain length).
    However, I can tell you with full confidence that the width issue is at least correct.
    Hope this helps!
    T
  5. AlanW

    AlanW Maximum Pace

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    7 vs 10 chain length

    The chain length depends on the difference between the smallest and largest cogs, both front and rear. The derailleur needs to be able to take up the slack in the chain.
    A 12-25, 7 speed cassette with require exactly the same chain length as a 12-25, 10 speed cassette. The benefit of 10 speeds is the gear ratios are closer, allowing the rider to stay closer to his or her ideal pedalling cadence (rpm).

    Chain length should be the length needed to go around the two largest cogs (front and rear), without passing through the rear derailleur, plus two links. It's explained in the instructions that come with shimano chains.
    AW.

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