General Cycling Discussion - What does the "C" mean in a tire size

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flanso
01-29-11, 12:19 PM
Some tires have the letter C following the width, 700 x 25c, for example. What does the C mean?

Shimagnolo
01-29-11, 12:23 PM
http://www.sheldonbrown.com/tire_sizing.html#french

JanMM
01-29-11, 12:42 PM
Can't remember if that is for Centrigrade or Celsius.:D
Trust Sheldon.

fietsbob
01-29-11, 12:43 PM
Guess they forbid teaching the Metric system in Florida,

as another step towards a UN world government.
:rolleyes::lol::roflmao:

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.

Shimagnolo
01-29-11, 12:46 PM
Guess they forbid teaching the Metric system in Florida,

Perhaps you should read the Sheldon link I posted, before criticizing other people.

fietsbob
01-29-11, 01:15 PM
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.

flanso
01-29-11, 04:00 PM
Take a look at the Nashbar site, http://www.nashbar.com/bikes/TopCategory_10053_10052_200327_-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?

LesterOfPuppets
01-29-11, 04:05 PM
Take a look at the Nashbar site, http://www.nashbar.com/bikes/TopCategory_10053_10052_200327_-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.

Pobble.808
01-29-11, 04:06 PM
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.

LesterOfPuppets
01-29-11, 04:06 PM
Guess they forbid teaching the Metric system in Florida,

The "c" on tire sizes has nothing whatsoever to do with the metric system.

LesterOfPuppets
01-29-11, 04:07 PM
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.

Pobble.808
01-29-11, 04:19 PM
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?

LesterOfPuppets
01-29-11, 04:22 PM
I always figured they were the same C, just put in the wrong place by someone.

009jim
01-29-11, 04:26 PM
I'll take a shot at this and suggest that "c" could be a measure of the height to width ratio.

prathmann
01-29-11, 04:54 PM
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.

Retro Grouch
01-29-11, 05:40 PM
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.

JanMM
01-29-11, 07:05 PM
Agree that the 'c' just serves to confuse people. I'll take my 700 plain, please.

BlazingPedals
01-29-11, 08:36 PM
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.

JanMM
01-29-11, 09:24 PM
I've learned to talk about 406 and 559 so why not 622? Course, that will confuse some folks, too.

CB HI
01-30-11, 01:07 AM
Guess they forbid teaching the Metric system in Florida,

as another step towards a UN world government.
:rolleyes::lol::roflmao:

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. :rolleyes::lol::roflmao:

CB HI
01-30-11, 01:12 AM
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.

Jeff Wills
01-30-11, 07:38 PM
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 (http://www.bike-alog.com/)). 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.

killerB
08-01-13, 10:08 PM
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

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 400×20, HB 422×25, 620×13C

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

LesterOfPuppets
08-01-13, 10:19 PM
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

Oh boy. I always thought Crochet meant "hook" in French. How much more confusing can this possibly get? :)

ThermionicScott
08-01-13, 10:28 PM

Retro Grouch
08-02-13, 07:11 AM
Some tires have the letter C following the width, 700 x 25c, for example. What does the C mean?

It's a width size - like in shoes.

In this case, when the tire gets wider it also gets taller. A 700d tire has roughly the same circumference as a 700c, but it's bead diameter is smaller so a 700c tire won't fit on a 700d rim.

fietsbob
08-02-13, 09:52 AM
French sizing scheme : theres a 700 a & b and the C ..

ETRO is the agreement between Tire and Rim manufacturers ,
on dimensions to be compatible.

use those.. 622-25 mm in this example.. a better designation,

that will be molded into the tire, sidewall, itself, these days.

2 years on I hope the OP got this sorted by now..

killerB
08-02-13, 10:25 AM

If you know the correct information, it would be great to know what it is.

I wasn't posting that info because I claim that it's correct. I was posting it in the hopes that some brilliant individual such as yourself, would either confirm it, or provide the correct information so that I, and anyone else who is looking this up could LEARN it.

See how that works?

ThermionicScott
08-02-13, 10:30 AM
If you know the correct information, it would be great to know what it is.

I wasn't posting that info because I claim that it's correct. I was posting it in the hopes that some brilliant individual such as yourself, would either confirm it, or provide the correct information so that I, and anyone else who is looking this up could LEARN it.

See how that works?

The correct answer was in the second post, had you read it -- adding misleading information so that people would have to correct you is not the right way to stimulate learning.

killerB
08-02-13, 10:58 AM
The correct answer was in the second post, had you read it -- adding misleading information so that people would have to correct you is not the right way to stimulate learning.

OK, well I can see that you're in a great mood today!

I DID read the Sheldon Brown article, and have read every post in this thread. I, and the OP are looking for the meaning of the SECOND letter designation. i.e. 700x25C

If you're referring to this section of the article:

"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..."

It looks like that's in reference to the FIRST letter in the naming convention, because right below it, there's a chart listing 700 C, 650 B, etc.

Can you point this ignorant and apparently reckless disseminator of bad information to the part of the article where he explains the second letter?

If you're saying that they are one in the same, well then, I guess I learned something.

fietsbob
08-02-13, 11:10 AM
The plan, as I grasp it, was to have the nominal tire diameter be close..

so if a wide tire the rim is smaller , a thin tire the rim is larger .

the 600, 650 700 is approximate category for over-all Diameter of the wheel with the tire on it.

The 20" wheel, breaks down to be 406 and 451 rims wider tire on 406 , thinner tire on 451.. same sort of concept.

ThermionicScott
08-02-13, 11:10 AM
OK, well I can see that you're in a great mood today!

I DID read the Sheldon Brown article, and have read every post in this thread. I, and the OP are looking for the meaning of the SECOND letter designation. i.e. 700x25C

If you're referring to this section of the article:

"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..."

It looks like that's in reference to the FIRST letter in the naming convention, because right below it, there's a chart listing 700 C, 650 B, etc.

Can you point this ignorant and apparently reckless disseminator of bad information to the part of the article where he explains the second letter?

If you're saying that they are one in the same, well then, I guess I learned something.

And you're a really demanding newbie. :rolleyes:

The convention is to move the "C" after the tire width when it is discussed specifically, as in 700x32C or 650x42B. Don't ask me why, ask the French -- they came up with this system long before hooked rims existed.

killerB
08-02-13, 11:55 AM
That makes sense. Well , as much sense as random French sizing standards can. Thanks for confirmation.

dramiscram
08-02-13, 12:23 PM
'C' is for 'Caoutchouc'. It's a french word...:)

http://fr.wikipedia.org/wiki/Caoutchouc_(mat%C3%A9riau)

Wilfred Laurier
08-03-13, 11:31 AM
'C' is for 'Caoutchouc'. It's a french word...:)

http://fr.wikipedia.org/wiki/Caoutchouc_(mat%C3%A9riau)

wrong
the c stands for calice
the french word for chalice
used as an explitive in french canada
uttered the first time they saw how fast a road bike was

steve0257
08-03-13, 12:58 PM
The "c" denotes the optimal air temperature in Celsius for that particular tire's performance.

Sixty Fiver
08-03-13, 01:17 PM
In the modern day, the C means that the bead seat is 622mm and is a carry over from the French system for tyre sizing.

The 700A was 642, 700B was 635 which is a roadster tyre, and the 700D was a very wide tyre on a 584 rim that GT played with that is very close to the 650B which is now getting used on more off road bikes and seeing a resurgence on other bicycles.

If the designation has a C it fits a 622 rim.

Although I prefer using ISO measurements it is helpful to know the traditional measurements.

Sixty Fiver
08-03-13, 01:17 PM
wrong
the c stands for calice
the french word for chalice
used as an explitive in french canada
uttered the first time they saw how fast a road bike was

Then the C should have been an S for Sacrament !!!

fietsbob
08-03-13, 03:27 PM
S for Sacrament

Yea but the tire factories are in SE Asia, where the rubber plantations are,
it was never part of the Holy Roman Empire