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  1. #1
    Slow Moving Vehicle Jean Beetham Smith's Avatar
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    How sharp is too sharp?

    We all know not to ride big ring-big sprocket or small ring-small sprocket because the chain is at too sharp an angle. Richard Ballantine in Richard's 21st Century bicycle book says that triple chain rings on 7,8, or 9 speed blocks you should avoid 2 cogs on either side of the extreme, and that the middle ring shouldn't be used with the extreme cogs either. Is there a rational way of figuring out which angles are too extreme? Does the chain width effect the acceptable angles? Does anybody really know these things or is it all trial & error? If so, why don't production bikes come with charts of the "right" gear combos and the no-nos?

  2. #2
    Chi-Chi Monger *WildHare*'s Avatar
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    A little trial and error I would say. You can really see when you are cross chaining badly. There really is no need for it. You should be able to find a comfortable gear without going to extremes. Personally, I ride 1-4 on the granny gear, 3-6, maybe 7th on the middle ring and 5-8 on the big ring. Just experiment...
    When it's good it's really good...And when it's bad I go to pieces - David Bowie

  3. #3
    Senior Member pat5319's Avatar
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    Using the inside to outside small to small etc. combinations are a bad ida on 2 chainring bikes as well. On five, six and 7 speed compact clusters do not use one outer or inner cog with the opposite chianring. On 7,8,9 speed clusters two cogs.
    My chain rubs on the outer chainring if I try to use either of my outer two cogs when I'm in my small chainring on my 53/39 X 13-23 set-up and others.
    Extreme angles cause-
    Uneven pressure, thus quicker wear on the bushings in the chainlinks. ( That's where "chain-stretch" comes from).
    The chain plates to rub and erode the chain-ring and cogset teeth and against each other.

    Ride that chain-line straight
    Pat
    Pat5319


  4. #4
    Banned
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    You should be able to use ALL cogs when you are in the middle ring of a triple ring bike.
    Je vais à vélo, donc je suis!

  5. #5
    Senior Member Greg's Avatar
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    I was going to post a thread on why I can't adjust my Ultegra triple to quiet down when at the extremes.

    Now, I find I shouldn't be there in the first place.

    Once again, unexpectantly, I've learned something new.

    Thanks all.

  6. #6
    feros ferio John E's Avatar
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    Allowable chain angles are a function of lateral chain flexibility and chainring tooth profile. I agree that one should avoid the large/large and small/small combinations on almost any modern derailleur bicycle, but which (if any) other combinations to avoid depends also on chainstay length, chainring size difference, cogset width, and chainring-to-cog alignment. If you can make the chain run quietly and if it stays on the chainring when you backpedal, you are in a usable gear.

    Both of my road bikes, which use 8-tooth chainring drops (50-42 and 52-44) and mid-size 7-speed freewheels (13-26 and 14-28), work well in all combinations except large/large. On my 3/7 mountain bike (48-40-24 / 13-26), I avoid 24/13, 24/15, and 48/26.

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