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700x23/25 etc... what do the numbers stand for ?(17 posts)

700x23/25 etc... what do the numbers stand for ?blakester
Jun 2, 2003 7:50 PM
What measurement is used, and what is measured?
Size of tire.the bull
Jun 2, 2003 8:06 PM
700 mm rim
23 or 25mm width
This must be a tube it will work with standard road tire
23 to 25mm in width
Is it wheel circumfrence (700) Is it 23mm wide when inflated? nmblakester
Jun 2, 2003 10:25 PM
Jun 3, 2003 4:18 AM
I believe its circumference (700) and height when inflated(23). Of course, taller tires tend to be wider. And just like everything else in cycling, the measurments are not very standard (i.e., there can be large differences in what one mfg's 23 is versus another --- just compare a Michelin to a Continental).
23 mm is the width when inflated. I've measured them withPaul
Jun 3, 2003 4:39 AM
vernier calipers and some are right on, and some are off by a mm or two. Did you make it to Point of Rocks? Myself and a friend did Harmony Church loop from my house, it was so windy, that I had to brake for fear of being blown off the road.
Thats coincidencepmf1
Jun 3, 2003 5:00 AM
I'm pretty sure its height, but have never tried calipers.

I worry about you sometimes. Maybe you need to get out of the basement and travel someplace with your wife.

I got out Saturday and rode 40 miles. Got home just before it started raining. I bagged it Sunday. The wind was just too crazy. I think I'm getting a chest cold anyway.
The REAL answerAlexx
Jun 3, 2003 4:20 AM
The 700x25 refers to the following:

700c tire: meaning, the diameter of the tire is roughly about 700mm in the old French measuring system, back when tires were much larger, and were always tubulars. The "c" designation is one that is always used on modern clinchers (although there is an obsolete 700b convention...)Essentially, this number is now meaningless, since any road tire is less than 700mm in diameter. The diameter if the rim is 622mm.

The 25 comes from the ERTRO number (more about that in a minute...), which refers to the tire's profile height, NOT the width. They are often close, but they are not the same.

Somewhere on the tire will be the ERTRO number. This nuber (for the tire described) will say "622-25", and is usually only stamped in the rubber. Once again, the 25 refers to the profile height, not the width. With the ERTRO number, you can quickly calculate the true diameter of the tire, by adding 2*profile height to the diameter. 622mm + 2*25mm = 672mm. You can use this to adjust your speed and mileage computer.
The REAL answer<-It's width, not height!russw19
Jun 3, 2003 9:54 AM
The following is not my own work.. it is a cut and paste from Sheldon Brown's work on the Harris Cyclery site.

The ISO (E.T.R.T.O.) System:
ISO, the International Organization for Standardization has developed a universal tire sizing system that eliminates this confusion. (This system was formerly known as the "E.T.R.T.O." system, developed by the European Tyre and Rim Technical Organization.)

The ISO system uses two numbers; the first is the width of the tire or rim in millimeters (The actual tire width will vary a bit depending on the width of the rim. The rim width is measured between the flanges.)

The second ISO number is the critical one, it is the diameter of the bead seat of the rim, in mm. Generally, if this number matches, the tire involved will fit onto the rim; if it doesn't match, the tire won't fit.

For example, a 700 x 20 C road tire would be a 20-622; a 700 x 38 hybrid tire would be a 38-622. The width difference between these sizes would make them less-than ideal replacements for one another, but any rim that could fit one of them would work after a fashion with the other.

The following is a partial listing of traditional tire sizes that are sometimes seen in the U.S., with their ISO bead seat equivalents.
Jun 3, 2003 10:08 AM
"The ISO system uses two numbers; the first is the width of the tire or rim in millimeters (The actual tire width will vary a bit depending on the width of the rim. The rim width is measured between the flanges.)"

I'm sorry, but Sheldon is wrong on this one. That number is the PROFILE HEIGHT in the ETRTO system.

BTW, I got my numbers reversed on my ETRTO number, as well as getting the acronym wrong.
Clarification: sorry, you are not correct....russw19
Jun 3, 2003 3:09 PM
Here's Michelin's say on it all... and they should be considered the final word as they invented the pnuematic replacable bicycle tire in 1891. This is from their FAQ.

What do the various markings on the tire's sidewall mean?

Michelin tires are sold in dozens of countries around the world, so they must conform to the marking standards of all these various nations. Luckily for North American consumers, the marking standards are relatively straightforward.
Road tires: Nearly all road bikes sold in North American bike shops use what are commonly known as "700C" tires. The number refers to the approximate outside diameter of the tire, in millimeters. The "C" indicates that it has an inside (or bead-seat) diameter of 622mm. In Europe, there are also tires with "A" and "B" inside diameters, but bikes using these sizes are not generally available in North America. Adding to the confusion is the fact that a 650C tire and a 700C tire do not use the same size rim. The width of a 700C tire is also expressed in millimeters, so a 700Cx23 tire is 700mm in diameter, by 23mm wide. Prior to the late 1970s, the tires and wheels of all bikes sold in the U.S. were measured in inches, i.e. 27x1, and many inexpensive bikes sold through discount stores still use this system. Even though a 27-inch wheel and a 700C wheel appear similar in size, their tires are not interchangeable. Michelin does not offer 27-inch tires.

Mountain bike tires: While metric sizing standards for off-road tires do exist, mountain bike tires are more commonly known as "26-inch" tires, though that number refers neither to the diameter of the rim nor that of the tire. Section widths of mountain bike tires are also expressed in inches, so a 26x2.1 tire is nominally 2.1 inches wide.

ETRTO markings: The European Tire and Rim Technical Organization has attempted to standardize the various marking systems used internationally, but widespread acceptance of the ETRTO standard has been slow in coming. The ETRTO system consists of two numbers: 50-559, for example. The first number (50) is the nominal section width of the tire, in millimeters. The second number (559) is the inside diameter of the tire, also in millimeters. The standard ETRTO diameters for tires sold in North America are 559mm (mountain bike) and 622mm (road bike). All Michelin tires are marked with ETRTO dimensions, in addition to the markings mentioned above.

Sorry, but I trust Michelin over everyone else here.. well, I trust Sheldon over most of you too, but this is the definitive answer from the guys who invented not only the bike tire, but helped come up with the standard in question.

Seems a little vague for a "final word"...TFerguson
Jun 3, 2003 4:35 PM
as well as contradictory.

"The "C" indicates that it has an inside (or bead-seat) diameter of 622mm."

"Adding to the confusion is the fact that a 650C tire and a 700C tire do not use the same size rim."

Try re-reading the article, it's clear.russw19
Jun 3, 2003 10:55 PM
No contradiction at all. Reread the article. It's perfectly clear. You eliminated the answer in your cut and paste.

When talking about the 700C rim, the C indicates that the rim has a bead seat of 622mm. The tire must have a larger diameter as it fits around the rim. Therefore the rim must be smaller. But there were (are) at least 4 different variations of the 700 wheel. A,B,C,and D. The "C" designation uses the above mentioned 622 mm bead seat.

There are also at least 3 versions of the 650 diameter wheel as well. A,B, and C. So the part about "adding to the confusion" is simply telling you not to confuse a 650C tire (which has a bead seat diameter of 571mm) with that of a much larger 700C tire. The C is not the same, just as the 650 and 700 are not the same. No contradiction, and not really that confusing. Read the article at the link Doug Sloan posted. It makes all this seem easy as pie.

But the point is that a 700C x 23 Tire means the tire's bead is 622mm and will fit a 700C rim, and the tire is 23mm wide, not high.

The other "REAL answer"the bull
Jun 3, 2003 6:13 PM
Hey I saw this pic and I thought of this post!
complete info from SheldonDougSloan
Jun 3, 2003 6:16 AM
Seems like width is more important measurement !the bull
Jun 3, 2003 8:58 AM
As a tire is wider it also gets taller.
Read an article about conti's(attack/force) frt and rear tires.
They mention the fact that there tires are 22mm width in frt.and 23mm width in rear.
Oh well who really cares.
28 mm tires on rims 13 mm wide rimsContinental
Jun 3, 2003 2:11 PM
Sheldon's site has atable of recommended tire sizes for various rims widths. It shows that a 28 mm wide tire is not a safe fit for a 13 mm wide rim. I've never heard of this limitation, and never considered rim width when changing from 23 mm tires to 28 mm. No problem so far. Anyone else have experience with wider tires on narrow rims?
Thats a thin rim!!! nmthe bull
Jun 3, 2003 2:16 PM