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On a 10 speed road bike, what is the ideal chain tension?

I was recently told (by a bike shop) that my rear derailleur should be fully extended (pointing forward) when the chain is between the 2 biggest cogs.

Does a riding with high tension decrease your chain life quicker? It seems logical that it would, so perhaps I was given bad advice.

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    Really you think that little spring puts tension on a chain that even compares to pedaling the bicycle. – paparazzo May 27 '15 at 19:43
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    You have a complete guide for chain length here: parktool.com/blog/repair-help/chain-length-sizing It does not have necessarily to be with chain wear but rather with overall system performance (in extreme cases, you won't be able to use certain combinations of gears, such as big in the front and big in the back). – super May 27 '15 at 20:45
  • thanks for the parttool link, thats the best explanation ive seen of how to do that – mkoryak May 27 '15 at 21:29
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The chain should be as short as possible and as long as necessary. It will usually shift better with proper tension. The tension shouldn’t affect chain life though the shorter chain will. Make a 104 link chain shorter by 2 links and it has almost 2% less material and thus shorter life. But that’s really a small effect.

I can dimly remember an article which stated that higher tension (they tested big chainring vs. small chainring) is actually more efficient, probably because there are less vibrations.

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The tension generated by the derailleur does not have any effect on chain wear, its insignificant compared to what a rider places on the chain when pedaling.

However, riding in that configuration (big to big) is called cross chaining. Cross chaining increases the wear on the chain due to the increased angles where the chain comes onto the chain rings and cogs. Although not as bad as some say, its less than desirable to spend long periods of time cross chained.

  • Not as bad as some say, I agree, but keep in mind in a single speed bike the chain will last at least twice as much, sometimes 3 or 4 times more, comparing with a geared system, using the exact same chain (single-speed specific chains have stronger links). This is mostly due to cross chaining (after all, cross chaining is how you measure chain wear). – super May 27 '15 at 20:50
  • but then you have to ride a single speed – mattnz May 27 '15 at 21:17
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    @super - do you have data to back this claim up? I have actually been measuring chain wear versus mileage and duration across a variety of setups, including single speeds for a few years now. I have not seen any results that would come close to backing your claim. You are expounding opinion as fact. – Rider_X May 27 '15 at 21:27
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    Sorry for giving two answers. On KMC website (kmcchain.eu/chain_wear), most tips for preventing chain wear come from good shifting. In a SS this is simply not a problem. My personal observations also verify this. Just imagine the lateral forces a geared system puts on the chain, and the impact that has on wear. And we aren't even talking about specific SS chains, which can be bulkier because don't have to support shifting through lateral flexibility. I am sorry this is the only way I have to support my claim, as I am not aware of a complete side-by-side test. – super May 27 '15 at 21:47
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    Time to end this OT discussion. The OP's Question was about a geared bike and has nothing to do with a Single Speed. – mattnz May 27 '15 at 22:47

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