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  1. #1
    Senior Member
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    What does the "C" mean in a tire size

    Some tires have the letter C following the width, 700 x 25c, for example. What does the C mean?

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    Senior Member Shimagnolo's Avatar
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    rebmeM roineS JanMM's Avatar
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    Can't remember if that is for Centrigrade or Celsius.
    Trust Sheldon.
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    coprolite fietsbob's Avatar
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    Guess they forbid teaching the Metric system in Florida,

    as another step towards a UN world government.







    by the way the C needs to be behind the 700, not the 25..

    actual would be 622-25, imprinted on the tire; ... ETRO Standard, bead seat diameter and tore width in mm.
    Last edited by fietsbob; 08-02-13 at 08:49 AM.

  5. #5
    Senior Member Shimagnolo's Avatar
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    Quote Originally Posted by fietsbob View Post
    Guess they forbid teaching the Metric system in Florida,
    Perhaps you should read the Sheldon link I posted, before criticizing other people.

  6. #6
    coprolite fietsbob's Avatar
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    I'm bilingual, fractional and metric, and not humor impaired..
    no, It was the South I was making the joke about.
    their leaders are usually talking weird.

  7. #7
    Senior Member
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    Take a look at the Nashbar site, http://www.nashbar.com/bikes/TopCate...27_-1_200276_N
    Expand "by size" on the left side of the page. You will see, for example, separate listings for 700x23 and 700x23c. The same for many other widths; some with c and some without. My question is, whats the difference between the sizes with and without the c?

  8. #8
    Quirky Grifter LesterOfPuppets's Avatar
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    Quote Originally Posted by flanso View Post
    Take a look at the Nashbar site, http://www.nashbar.com/bikes/TopCate...27_-1_200276_N
    Expand "by size" on the left side of the page. You will see, for example, separate listings for 700x23 and 700x23c. The same for many other widths; some with c and some without. My question is, whats the difference between the sizes with and without the c?
    No difference. Strictly a data entry / database records anomaly.
    1980ish Free Spirit Sunbird fixed * 1996 Mongoose IBOC Zero-G * 1997 KHS Comp * 1990-ish Scapin * Lemond Buenos Aires Triple

  9. #9
    alleged person Pobble.808's Avatar
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    Quote Originally Posted by Shimagnolo View Post
    Perhaps you should read the Sheldon link I posted, before criticizing other people.
    It looks like there has been a misunderstanding here. If I read Sheldon's link correctly, he was referring to the ABCDs that follow the tire's three-digit diameter dimension (700C, 700D etc). The OP was asking about the c in 700 x 25c, which presumably refers to the nominal width in centimeters.

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    Quirky Grifter LesterOfPuppets's Avatar
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    Quote Originally Posted by fietsbob View Post
    Guess they forbid teaching the Metric system in Florida,
    The "c" on tire sizes has nothing whatsoever to do with the metric system.
    1980ish Free Spirit Sunbird fixed * 1996 Mongoose IBOC Zero-G * 1997 KHS Comp * 1990-ish Scapin * Lemond Buenos Aires Triple

  11. #11
    Quirky Grifter LesterOfPuppets's Avatar
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    Quote Originally Posted by Pobble.808 View Post
    It looks like there has been a misunderstanding here. If I read Sheldon's link correctly, he was referring to the ABCDs that follow the tire's three-digit diameter dimension (700C, 700D etc). The OP was asking about the c in 700 x 25c, which presumably refers to the nominal width in centimeters.
    A 25 cm tire would be almost 10" wide.
    1980ish Free Spirit Sunbird fixed * 1996 Mongoose IBOC Zero-G * 1997 KHS Comp * 1990-ish Scapin * Lemond Buenos Aires Triple

  12. #12
    alleged person Pobble.808's Avatar
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    Quote Originally Posted by LesterOfPuppets View Post
    A 25 cm tire would be almost 10" wide.
    Good point, but the c in 700x25c is presumably not the same as the 700C etc -- so what is it?

  13. #13
    Quirky Grifter LesterOfPuppets's Avatar
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    I always figured they were the same C, just put in the wrong place by someone.
    1980ish Free Spirit Sunbird fixed * 1996 Mongoose IBOC Zero-G * 1997 KHS Comp * 1990-ish Scapin * Lemond Buenos Aires Triple

  14. #14
    Senior Member 009jim's Avatar
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    I'll take a shot at this and suggest that "c" could be a measure of the height to width ratio.

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    LesterOfPuppets is correct - the 'c' following the tire width (given in mm) is just incorrect but unfortunately the error is becoming more common and has been copied by some tire manufacturers who should know better. As Sheldon's site states, the 'c' in wheel diameter sizes (700c, 650c) was originally an indication of the width with a variety of possible sizes 700a, 700b, 700c, etc. each having about the same total diameter, incl. the tire, but with varying tire widths. Only the 'c' size has survived of the various 700x sizes, but we still have both 650b and 650c. There is no reason for anyone to put a 'b' or a 'c' behind the tire width.

    Things would be much clearer if we all switched to the ISO specifications giving the actual bead seat diameters of the rim in mm, i.e. 23-622 is a tire with a width of 23mm that fits on a rim with a bead seat diameter of 622mm.

  16. #16
    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by LesterOfPuppets View Post
    The "c" on tire sizes has nothing whatsoever to do with the metric system.
    Yeah, it's actually more closely related to shoe width sizes as in ABCD.

  17. #17
    rebmeM roineS JanMM's Avatar
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    Agree that the 'c' just serves to confuse people. I'll take my 700 plain, please.
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  18. #18
    Senior Member BlazingPedals's Avatar
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    Quote Originally Posted by JanMM View Post
    Agree that the 'c' just serves to confuse people. I'll take my 700 plain, please.
    If you're going to get rid of the ABCD, then just go by the ETRTO. Instead of 700C, call it what it is: a 622mm rim. It's already on the tire.

  19. #19
    rebmeM roineS JanMM's Avatar
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    I've learned to talk about 406 and 559 so why not 622? Course, that will confuse some folks, too.
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  20. #20
    Cycle Year Round CB HI's Avatar
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    Quote Originally Posted by fietsbob View Post
    Guess they forbid teaching the Metric system in Florida,

    as another step towards a UN world government.
    Quote Originally Posted by fietsbob View Post
    I'm bilingual, fractional and metric, and not humor impaired..
    no, It was the South I was making the joke about.
    their leaders are usually talking weird.
    I agree with you. Such foolish post as yours are very humorous.
    Land of the Free, Because of the Brave.

  21. #21
    Cycle Year Round CB HI's Avatar
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    Quote Originally Posted by JanMM View Post
    I've learned to talk about 406 and 559 so why not 622? Course, that will confuse some folks, too.
    But learning the ISO numbering can save a person from buying the wrong size tire.
    Land of the Free, Because of the Brave.

  22. #22
    Insane Bicycle Mechanic Jeff Wills's Avatar
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    Quote Originally Posted by LesterOfPuppets View Post
    No difference. Strictly a data entry / database records anomaly.
    Agreed. Interpreting and straightening out databases of bicycle parts information used to be my job (long ago, at Bike'alog). Unless the tire is really unusual, 700 x **C is the same as 700 x **.

    I agree with Blaze, too: ETRTO makes life easy. It makes explaining the compatibility of 700C tires (such as 700x35C aka 35-622) and 29" tires (such as 29 x 2.0" aka 55-622) much easier to comprehend.
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  23. #23
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    I know this is an old thread, but since it's currently the first hit that comes up in The Google:

    From The Wikipedia:

    ISO 5775-2 defines designations for bicycle rims. It distinguishes between

    • Straight-side (SS) rims
    • Crochet-type (C) rims
    • Hooked-bead (HB) rims

    Rims are designated by their nominal rim diameter and their nominal width, separated by a cross (). Both are measured in millimeters. The rim type codes SS or HB precede the rim designation, whereas code C is appended to the nominal width.

    Examples:

    SS 40020, HB 42225, 62013C

    The nominal width of a rim is the inner width between the straight sides or beads as one can easily measure it with a caliper (see the standard for drawings and exact measurement procedures).



    The standard widths of straight-side rims are:

    18, 20, 22, 24, 27, 30.5The standard widths of crochet-type rims are:
    13C, 15C, 16C, 17C, 19C, 21C, 23C, 25C

    http://en.wikipedia.org/wiki/ISO_5775

  24. #24
    Quirky Grifter LesterOfPuppets's Avatar
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    Quote Originally Posted by killerB View Post
    I know this is an old thread, but since it's currently the first hit that comes up in The Google:

    From The Wikipedia:

    ISO 5775-2 defines designations for bicycle rims. It distinguishes between

    • Straight-side (SS) rims
    • Crochet-type (C) rims
    • Hooked-bead (HB) rims
    Oh boy. I always thought Crochet meant "hook" in French. How much more confusing can this possibly get?
    1980ish Free Spirit Sunbird fixed * 1996 Mongoose IBOC Zero-G * 1997 KHS Comp * 1990-ish Scapin * Lemond Buenos Aires Triple

  25. #25
    7-speed doomsday prepper ThermionicScott's Avatar
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    Oh good, a thread bumped to add incorrect information.
    Quote Originally Posted by chandltp View Post
    There's no such thing as too far.. just lack of time
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