General Cycling Discussion - 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?

http://www.sheldonbrown.com/tire_sizing.html#french

Can't remember if that is for Centrigrade or Celsius.:D
Trust Sheldon.

Guess they forbid teaching the Metric system in Florida,

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

Guess they forbid teaching the Metric system in Florida,


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

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.

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?

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.

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.

Guess they forbid teaching the Metric system in Florida,

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

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.

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?

I always figured they were the same C, just put in the wrong place by someone.

I'll take a shot at this and suggest that "c" could be a measure of the height to width ratio.

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.

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.

Agree that the 'c' just serves to confuse people. I'll take my 700 plain, please.

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.

I've learned to talk about 406 and 559 so why not 622? Course, that will confuse some folks, too.

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:

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.

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.