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Thread: Tire question?

  1. #1
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    Tire question?

    Buying a Cyclocross bike and the tire size is a 700X35c.

    What does the "c" represent?

    Thanks

  2. #2
    hispanic mechanic
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    Nothing, really. A,B,C, and D were arbitrary assignments.

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  3. #3
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    Tire Sizing Systems

    "In the French system, the first number is the nominal diameter in mm, followed by a letter code for the width: "A" is narrow, "D" is wide. The letter codes no longer correspond to the tire width, since narrow tires are often made for rim sizes that originally took wide tires; for example, 700 C was originally a wide size, but now is available in very narrow widths, with actual diameters as small as 660 mm."

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    If they wrote it as "700x35c," they are writing it incorrectly. Unfortunately, it is extremely common to see it written as such.
    What they meant was "700cx35."
    700c is the nominal rim size. There were, at one time, 700a, 700b, 700c, and 700d sizes. All were different diameters. Despite GT selling a couple of hybrid 700d bikes in the early 90s, all the 700 sizes have died out except for the venerable 700c, which you will find on just about every road bike, cross bike and all 29er bikes.
    The idea with the "700" number is that 700a would have a large diameter rim and a very thin, narrow tire. The overall height of the tire, when inflated was about 700mm. The 700b, c and d sizes would have progressively smaller diameter wheels, and progressively fatter, higher volume tires. But, the overall height of the wheel, with inflated tire, would be pretty much identical across the board.
    Pretty much the same thing happened with 650. There were once several different 650 sizes. Now, 650c is used on some triathalon bikes and smaller-sized road bikes. 650b is a European touring tire size, and is rapidly gaining steam as the "new" American mountain bike size.
    Even though that's how the system started, things got pretty muddied up along the way. Hard to think of a 700c tire being very high volume, when you see all these roadies on 23mm wide tires. And 650b tires are usually much fatter than 650c. Oh well, I guess it made sense for a few years, about a hundred years ago!

  5. #5
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    Quote Originally Posted by mhickey79 View Post
    If they wrote it as "700x35c," they are writing it incorrectly. Unfortunately, it is extremely common to see it written as such.
    What they meant was "700cx35."
    Not quite. The correct and accurate size would be 35-622.
    The 700x35 is still the obsolete but common labeling. Sometimes 700x35c is used with the "c" in this case meaning it is a clincher tire.
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  6. #6
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    That totally makes sense since many of the tire manufaturers as well as bike companies, refer to the Cyclocross tire as being a 700X35c.

    So the 35 is the width in mm, meaning 35mm = 1.37 inches?

  7. #7
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    Quote Originally Posted by rickcin View Post
    That totally makes sense since many of the tire manufaturers as well as bike companies, refer to the Cyclocross tire as being a 700X35c.

    So the 35 is the width in mm, meaning 35mm = 1.37 inches?
    The width of 700C tires is always expressed in mm.
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  8. #8
    jrm
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    Sheldon mentions that the "C"

    was for width like with shoes. If by ISO standards a tire is measured as 35-622..35 being the OD and 622 being the ID then wouldnt C be some kinda of aspect ratio?
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  9. #9
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    Quote Originally Posted by jrm View Post
    was for width like with shoes. If by ISO standards a tire is measured as 35-622..35 being the OD and 622 being the ID then wouldnt C be some kinda of aspect ratio?
    No. 35 is the section width, not the OD (35mm is larger than 622mm? ). There is no ISO size for outside diameter. Just section width and bead seat diameter (622).

    Aspect ratio, as used for car tires, is useless for bicycle tires because of the round casing profile. There is very little variation in the tire casing height to width ratio.

    Go reread Sheldon's tire info for the explanation of the obsolete A, B and C sizing.
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  10. #10
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    Quote Originally Posted by shiggy View Post
    The width of 700C tires is always expressed in mm.
    Except when they are called 29er tires and labelled as 29x2.1, etc.

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