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  1. #1
    Member fatman's Avatar
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    Do no croos big chainring with big rear cog, then, Why are bikes called 27 speeds?

    In the case of a 3 chainrings front, 9 cogs rear cassette bike. If you can not use all the chainrings in convination with all the rear cogs, Why are bike called 27 speeds?

    For example the manual of my bike said that you should not cross the chain with the big chainring and the big rear cog. I have done this and sometime I get into trouble.

  2. #2
    The Red Lantern Rev.Chuck's Avatar
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    Because it is easier than figuring out exactly how many "effective" gears a bike has for all the different combos there are based on the three front rings, 20t to 56t and nine cassete cogs 11t to 34t. You realize that there are similar gear combos in all three rings, you only have about 17 gears.
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  3. #3
    60mph in the 42 ring! Dave Stohler's Avatar
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    Only neophytes or ignoramuses use the term "27 speed". To the cyclist community, it's a "9-speed with a triple".
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  4. #4
    The Flying Scot chewa's Avatar
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    Quote Originally Posted by Dave Stohler
    Only neophytes or ignoramuses use the term "27 speed". To the cyclist community, it's a "9-speed with a triple".
    Or traditionalists, surely Dave.

    I grew up in the era of the 10 speed, and I still occasionally refer to 27 speed. But then I still ask for a block rather than a cassette.
    plus je vois les hommes, plus j'admire les chiens

    1985 Sandy Gilchrist-Colin Laing built 531c Audax/fast tourer.
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  5. #5
    Crank Crushing Redneck SamDaBikinMan's Avatar
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    It is marketing hype! There is not such thing as a 27 speed bike.
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  6. #6
    It tastes like burning! deliriou5's Avatar
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    Quote Originally Posted by Rev.Chuck
    Because it is easier than figuring out exactly how many "effective" gears a bike has for all the different combos there are based on the three front rings, 20t to 56t and nine cassete cogs 11t to 34t. You realize that there are similar gear combos in all three rings, you only have about 17 gears.
    Wow... if a triple has only 17 effective gears, then how many does a double have!!??

    And how "bad" is it really to be in big ring big cog? I've done it a couple times, but only for a couple seconds at a time...
    The only true knowledge is knowing that you know nothing - Socrates

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  7. #7
    05 Roubaix Comp Double
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    18 of course

  8. #8
    The Flying Scot chewa's Avatar
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    Depending on your chainring sizes and cassette ratios it is quite conceivable that, if you ride so as to prevent cross chaining, a triple front with 8 or 9 sp rear could realise as few as 12 - 14 gear ratios which are significantly different from others, with many more combo's giving similar gears.

    I use my triple (when commuting I lock out the smallest chainring) and 8 sp rear as 3 sets of 5 gears, outer 5 for the outer ring, middle 5 or six for the middle, inner 5 for the small ring, and don't really go outwith that.

    With a new chain, you can really feel when you cross chain, even with today's more flexible links.
    plus je vois les hommes, plus j'admire les chiens

    1985 Sandy Gilchrist-Colin Laing built 531c Audax/fast tourer.
    1964 Flying Scot Continental (531)
    1995 Cinelli Supercorsa (Columbus SLX)
    1980s Holdsworth Mistral fixed (531)
    2005 Dahon Speed 6 (folder)
    (YES I LIKE STEEL)
    2008 Viking Saratoga tandem
    2008 Micmo Sirocco Hybrid (aluminium!)
    2012 BTwin Rockrider 8.1

  9. #9
    It tastes like burning! deliriou5's Avatar
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    so from what i gather the purpose of the triple is not so much to provide you with a greater number of gear ratios as it is to give you a wider range of ratios
    The only true knowledge is knowing that you know nothing - Socrates

    Back on the bike!!

  10. #10
    Senior Member joeprim's Avatar
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    Quote Originally Posted by deliriou5
    so from what i gather the purpose of the triple is not so much to provide you with a greater number of gear ratios as it is to give you a wider range of ratios
    That's the way I view it. Although you do get more. But to be sure calculate all the ratios you have and see how many unique useable ones you have.

    Joe

  11. #11
    Member fatman's Avatar
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    Quote Originally Posted by chewa

    I use my triple (when commuting I lock out the smallest chainring) and 8 sp rear as 3 sets of 5 gears, outer 5 for the outer ring, middle 5 or six for the middle, inner 5 for the small ring, and don't really go outwith that.
    Hey! I like that I will use it as a rule.

  12. #12
    Senior Member miamijim's Avatar
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    The 'road' wheels for my mountain bike are setup.....a triple with a 9-speed rear that yields about 25 effective gears.

    What I did was use a cassette thats designed to pick-up where the previous chainring left off...

    The answer is yes, your bike does have 27 gear ratios...no 2 are exactly alike although many are very close.

    I didnt know I was an ignoramous......Oh, well.....
    WWW.CYCLESPEUGEOT.COM 2005 Pinarello Dogma; 1991 Paramount PDG 70 Mtb; 1976? AD Vent Noir; 1989 LeMond Maillot Juane F&F; 1993? Basso GAP F&F; 1989 Terry Symmetry; 2003 Trek 4700 Mtb; 1983 Vitus 979

  13. #13
    Devilmaycare Cycling Fool Allister's Avatar
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    My bike has only one speed - flat out.
    If we learn from our mistakes, I must be a goddamn genius.

  14. #14
    60mph in the 42 ring! Dave Stohler's Avatar
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    My touring bike uses a 6-speed rear, with half-step drops from a 4-tooth difference on the two big rings. Combine that with a 14-tooth drop to the granny gear, and I have a true 18 unique gear combos.
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  15. #15
    member Yo MikeOK's Avatar
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    You can use the big big if you have everything adjusted right, I do it occasionally in some situations but for no longer than I need to. It does put quite a strain on your drivetrain but it's a bike, not the space shuttle...

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