Bicycle Mechanics - How big are 700 CM tires?

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flameburns623
09-21-07, 06:41 AM
Hello!

Someone should've aborted the idiot who created the Metric system. So how big are 700 centimeter tires? I get the impression they are about 27 inchese but my tape measure shows me that 27 inches is about 69 centimeters--27-and-a-half inches is about 70 centimeters, BUT that's still off by a factor of ten. Unless I'm looking at really old-fashioned bikes, with seats several feet from the ground, somehting isn't quite right. From the photos I'm seeing, these are normal-sized bikes. So what's up? One web search seemed as if it suggested 700 centimeters was the WIDTH of the tires, but that would make the tires several FEET wide. Also seems improbable to say the least.

You know, for all the purported virtues of 'simplicity' with the metric system, the traditional measurments are usually much simpler: they were based, roughly, on anatomical or other familiar comparisons, and most folks could use fingers, arms, feet, etcetera to guestimate the approximate size of other objects. (No crude jokes, please).

tellyho
09-21-07, 06:48 AM
Check out this link. 700c tires are nowhere near 700 cm.

http://sheldonbrown.com/tire-sizing.html

well biked
09-21-07, 06:51 AM
Drop the M from 700CM. They're 700c, as in a, b, c, etc. They get the "700" from the fact that the outside diameter of the tire is around 700mm. If you don't like to call them 700c, you can call them by their more logical ETRTO name, which gives a tire's width and bead seat diameter, in millimeters. For a 700 x 28c tire, for example, that would be 28-622.

HillRider
09-21-07, 10:47 AM
Someone should've aborted the idiot who created the Metric system.
No, but it's something we Americans have to learn about since the rest of the workld uses it. Actually, the "English" measurement system we still use makes no logical sense at all and, while the Metric system is not completely logical, it is a whole lot better.

And as noted, 700c is not a measurement in cm.

Lunarist
08-29-09, 12:40 PM
while the Metric system is not completely logical

What's not logical about the metric system? I am not fully accustomed to it myself, but the conversion between units is so much easier than the imperial system.

bikinfool
08-29-09, 01:20 PM
Metric is much more logical than our dated English system, but there were a bunch of old farts in the US who should've been aborted for voting that conversion to metric down years back. Of course then there are some in Illinois who can't determine tire/wheel measurements without adding things into the mix that aren't relevant (let alone do any actual research)...as good an excuse for abortion as I can think of. :rolleyes:

Panthers007
08-29-09, 07:02 PM
622mm, or 62.2cm, is what a common 700C is really. One would think that the 'C' would refer to a metric measurement. But how could it? If C = cm = centimeter, you would have a 700 centimeter rim. And that's 275.59 inches! You'd need a step-ladder!

If you'd like a neat little converter for all-things-metric into more familiar things like inches an psi, here is a free download for your computer. Totally free and no nifty bugs, either:

DieselDan
08-29-09, 07:12 PM
The measurement is 700 MILLIMETERS.

Please, stop posting. You're reinforcing the negative dumb American stereotype.

Darth_Firebolt
08-29-09, 07:24 PM
The measurement is 700 MILLIMETERS.

Please, stop posting. You're reinforcing the negative dumb American stereotype.

The measurement is 622 MILLIMETERS.
Please, stop posting. You're reinforcing the negative dumb American stereotype.

Panthers007
08-29-09, 08:11 PM
The measurement is 700 MILLIMETERS.

Please, stop posting. You're reinforcing the negative dumb American stereotype.

:eek: :roflmao2: :roflmao2: :roflmao2: :roflmao: :eek:

Al1943
08-29-09, 08:20 PM
Drop the M from 700CM. They're 700c, as in a, b, c, etc. They get the "700" from the fact that the outside diameter of the tire is around 700mm.

Correct answer. 700mm includes a tire. It became a standard back when road tires were typically larger.

HillRider
08-29-09, 08:39 PM
What's not logical about the metric system? I am not fully accustomed to it myself, but the conversion between units is so much easier than the imperial system.
There are units that don't strictly follow the 10X, 100X, 1000X sequence like Angstroms and a few like Pascals that no one but a few scientists use but, as I said at first, the system is far more logical than the Imperial system we use here.

Actually we use both systems which is even more confusing. Soda comes in 2 liter bottles these days and booze in 750 ml, 1L and 1.75 L bottles. Metric bolts and other parts are common on "American" cars. We run 10K races. Etc.

waldowales
08-29-09, 08:46 PM
I'll put the popcorn in the microwave!

Jeff Wills
08-29-09, 08:48 PM
There are units that don't strictly follow the 10X, 100X, 1000X sequence like Angstroms and a few like Pascals that no one but a few scientists use but, as I said at first, the system is far more logical than the Imperial system we use here.

Actually we use both systems which is even more confusing. Soda comes in 2 liter bottles these days and booze in 750 ml, 1L and 1.75 L bottles. Metric bolts and other parts are common on "American" cars. We run 10K races. Etc.

Ya, you betcha. I work in a hospital pharmacy- for the most part, stuff comes in grams, milligrams, & micrograms. Some liquids still come in 1/2 quart (473ml) bottles. Every once in a while someone will ask for a grain (64.8mg) of something- at which point they're dragged outside and burned at the stake.

Al1943
08-29-09, 08:53 PM
We may use metric bolts in cars and metric sockets to turn the bolts, but the backside of the sockets will still be 1/2, 3/8, or 1/4 inch.
Most bicycle parts are metric except chains and steer tubes.

Jeff Wills
08-29-09, 09:01 PM
We may use metric bolts in cars and metric sockets to turn the bolts, but the backside of the sockets will still be 1/2, 3/8, or 1/4 inch.
Most bicycle parts are metric except chains and steer tubes.

HillRider
08-29-09, 09:25 PM
We may use metric bolts in cars and metric sockets to turn the bolts, but the backside of the sockets will still be 1/2, 3/8, or 1/4 inch.
Right, but I believe that even in the most metric of countries, ratchets are still made with 1/4", 3/8" and 1/2" square drives even if used exclusively with metric sockets.

As noted, some ISO bike standards are Imperial measurements like English bottom brackets, threaded steerers and freewheel threads. Even Italian bottom brackets aren't pure metric, being 36 mm x 24TPI.

Panthers007
08-29-09, 10:19 PM
As a chemist and die-hard science-head, I started using metric when I was 10. It makes perfect sense. Here is one of my favorite stories about how logical metric is, and how ding-dong Imperial is:

An English man named Fahrenheit took a tube with a bit of mercury in it that was sealed in a vacuum. Into this tube he etched numbers from, say, 0 to 250. Then he placed the tube into ice-water. The water was frozen at the 32 on his tube. Then he slowly brought the water to a rolling-boil. His tube said 212. So he recorded that 32(F) was the freezing point of water, and water boiled at 212(F).

Meanwhile a guy across the channel took a tube with a bit of mercury in it and sealed it in a vacuum. His name was Celsius. And he placed this tube into frozen water. He THEN etched '0' into the glass on his tube. And then he brought the water to a rolling-boil. He marked this as 100(C).

I'll leave it right here.

bleukahuna
08-29-09, 10:45 PM
Actually, there is quite a bit of imperial measure used in bikes. Pedals are 9/16-20 unless they are 1/2"-20 or french. 25.4mm handlebars are 1", seat posts are generally fractional inch sizes translated to mm, as are tubing sizes. One of the things that made french bikes weird was they were all metric.
Jeff, check your math. Down here we get 15.4 grains to the gram. I bet you meant milligrams.

Jeff Wills
08-29-09, 10:50 PM
Jeff, check your math. Down here we get 15.4 grains to the gram. I bet you meant milligrams.

You are correct! And I am over-caffeinated!!... like I said, I don't see grains much.

'Round here, we just say it's dope, yo.

urbanknight
08-29-09, 10:51 PM
Metric bolts and other parts are common on "American" cars. We run 10K races. Etc.
I used to have a 1989 Ford Taurus, and the first time I went to change the battery, I found that it had a metric bolt on one terminal and an SAE one on the other! :eek:

dabac
08-30-09, 03:00 AM
The measurement is 622 MILLIMETERS.
Please, stop posting. You're reinforcing the negative dumb American stereotype.

Well, stereotype or not, you've both gotten rule #1 of successfull quarreling down pat - it helps if you don't pay too much attention to what the opponent is actually saying...

HillRider
08-30-09, 07:22 AM
An English man named Fahrenheit took a tube with a bit of mercury in it that was sealed in a vacuum. Into this tube he etched numbers from, say, 0 to 250. Then he placed the tube into ice-water. The water was frozen at the 32 on his tube. Then he slowly brought the water to a rolling-boil. His tube said 212. So he recorded that 32(F) was the freezing point of water, and water boiled at 212(F).
Well he did it in 1724 so give him a bit of slack. The 0° point was the coldest he could get at the time which was a saturated ammonium chloride brine and he likely thought it was the coldest temperature obtainable with anything. It had the benefit of avoiding negative numbers. The remaining numbers were chosen to make creating the scale on the thermometer easy using the crude ruling methods available to him.

Meanwhile a guy across the channel took a tube with a bit of mercury in it and sealed it in a vacuum. His name was Celsius. And he placed this tube into frozen water. He THEN etched '0' into the glass on his tube. And then he brought the water to a rolling-boil. He marked this as 100(C).
The guy across the channel was in Sweden and Anders Celsius actually created a scale with 0° as the boiling point of water and 100° as the freezing point. The scale was reversed to our common usage after his death.

gearbasher
08-30-09, 07:36 AM
I used to have a 1989 Ford Taurus, and the first time I went to change the battery, I found that it had a metric bolt on one terminal and an SAE one on the other! :eek:

I have a 1960 Volvo, the engine bolts are SAE and the bolts on the body are metric.

DieselDan
08-30-09, 07:46 AM
Tires are 700mm. Rims are 622mm. The question was about tires.

Now, stop posting.

urbanknight
08-30-09, 08:23 AM
Tires are 700mm. Rims are 622mm. The question was about tires.

Now, stop posting.
Tires of different widths have different diameters.

LesterOfPuppets
08-30-09, 11:01 AM
No, but it's something we Americans have to learn about since the rest of the workld uses it. Actually, the "English" measurement system we still use makes no logical sense at all and, while the Metric system is not completely logical, it is a whole lot better.

There are good reasons for using using inches, as well. If you don't have well calibrated measuring tools, it's easier to accurately halve, quarter, etc. a given measurement than it is to divide it into 10 equal parts. That's one reason why decimal measuring systems had been promoted since the 18th century, but took a while to catch on.

In my line of work, goods are sold by the dozen, which used to really annoy me. Why can't they they sell them in tens? Then, as I gained experience working on different machines used to process these goods, it hit me. It's because 12 has way more denominators. Common variations of said machines can process 1, 2, 4, 6, 8 pieces at a time. Only the first two divide into 10 evenly, where as the first 4 divide into 12. 8 divides in evenly at 24, where it doesn't hit an even 10 'til 40.

HillRider
08-30-09, 01:08 PM
In my line of work, goods are sold by the dozen, which used to really annoy me. Why can't they they sell them in tens? Then, as I gained experience working on different machines used to process these goods, it hit me. It's because 12 has way more denominators. Common variations of said machines can process 1, 2, 4, 6, 8 pieces at a time. Only the first two divide into 10 evenly, where as the first 4 divide into 12. 8 divides in evenly at 24, where it doesn't hit an even 10 'til 40.
A number system based on 12 goes back to the Babylonians and still remains with us in our calendar (12 months) and clocks (12/24 hours, 60 minutes = 1/5 of 12, etc.) as well as eggs and baked goods.

JanMM
08-30-09, 01:10 PM
We in the States are lucky to be stuck with juggling two or more measuring systems for the foreseeable future: Recent research shows that mental activity can "dramatically delay the progress of Alzheimers' disease." The mental gymnastics required to go back and forth on a regular basis from Metric to Imperial/English etc. should help stave off dementia, at least for a while.

Jeff Wills: When someone requests drams or minims or grains etc, just respond with "No Habla Apothecary!"

LesterOfPuppets
08-30-09, 01:36 PM
A number system based on 12 goes back to the Babylonians and still remains with us in our calendar (12 months) and clocks (12/24 hours, 60 minutes = 1/5 of 12, etc.) as well as eggs and baked goods.

Don't forget everyone's favorites, beer and wine. The baked goods bit reminds me of quite possibly the worst decimal/non-decimal mismatch of all time: The 10-pack of hotdogs vs. the 8-pack of hotdog buns!

jonestr
08-30-09, 01:50 PM
There are units that don't strictly follow the 10X, 100X, 1000X sequence like Angstroms and a few like Pascals that no one but a few scientists use but, as I said at first, the system is far more logical than the Imperial system we use here.

Actually we use both systems which is even more confusing. Soda comes in 2 liter bottles these days and booze in 750 ml, 1L and 1.75 L bottles. Metric bolts and other parts are common on "American" cars. We run 10K races. Etc.

Angstrom is just 10^-10 meters and is commonly used as it is average (or most likely, I forget) distance of the electron from the proton hydrogen is ~.5Angstroms in the ground state (if I recall correctly), also it is not an official SI unit of measure.

a Pascal is just a Newton/1m^2 so I dont see what is crazy about that.

HillRider
08-30-09, 07:39 PM
Angstrom is just 10^-10 meters and is commonly used as it is average (or most likely, I forget) distance of the electron from the proton hydrogen is ~.5Angstroms in the ground state (if I recall correctly), also it is not an official SI unit of measure.

a Pascal is just a Newton/1m^2 so I dont see what is crazy about that.
The angstrom (10^-10 M or 10^-8 cm) isn't in the sequence of changing the prefix every 10^3 or 10^-3. Current usage is nanometers or 10^-9 and the Angstrom has fallen out of use.

The Pascal is a rational but limited use unit. Stop at any garage, even a European one, and ask them to adjust your tire pressure. Give them the desired pressure in Pascals (or Kilopascals if you prefer reasonable size numbers) and see the blank look.

Al1943
08-30-09, 07:51 PM
The Pascal is a rational but limited use unit. Stop at any garage, even a European one, and ask them to adjust your tire pressure. Give them the desired pressure in Pascals (or Kilopascals if you prefer reasonable size numbers) and see the blank look.

But in Europe they do understand bars, both types.

bikinfool
08-30-09, 08:24 PM
Stop at any garage, even a European one, and ask them to adjust your tire pressure. Give them the desired pressure in Pascals (or Kilopascals if you prefer reasonable size numbers) and see the blank look.

That's probably just from the asking...

Sluggo
08-30-09, 08:24 PM
Just to further stir the soup... my understanding is that the French devised a system in which there were several tire diameters, each of which had three widths. So 700A was intended to be the skinny tire, 700b was the medium, and 700c was the wide size; each of these were intended to have (approximately) the same outside tire diamater.

Practically speaking, it was easier to use the same rim diameter and design different width (and diameter) tires to fit the same rim. 700c became the standard, presumable because it was close to 27". Don't know if it was the same as tubular rims by design or by coincidence.

650a (26x1 3/8) 650b (26x1/2 [28 mm to ~40mm width]) and 650c (26xskinny, narrow tires for small frames) still exist, but not in the way that was originally envisioned.

jonestr
08-30-09, 08:39 PM
The angstrom (10^-10 M or 10^-8 cm) isn't in the sequence of changing the prefix every 10^3 or 10^-3. Current usage is nanometers or 10^-9 and the Angstrom has fallen out of use.

The Pascal is a rational but limited use unit. Stop at any garage, even a European one, and ask them to adjust your tire pressure. Give them the desired pressure in Pascals (or Kilopascals if you prefer reasonable size numbers) and see the blank look.

if you read back i said an Angstrom is not a SI unit, but it is frequently used. I dont see why that it doesent fall in the powers of 3 does not make it useful. I use "cm" all the time and am not too worried that I dont express them in meters or mm.

I guess it all boils down to using measurement systems that are of a good scale for what you are doing or fit your frame of reference.

Not too surprising that a tire shop uses something referenced to barometric pressure, but saying something like Pascals are some nonsensical unit is not really seeing it in terms of the units it is derived from.

Jeff Wills
08-30-09, 11:00 PM
Jeff Wills: When someone requests drams or minims or grains etc, just respond with "No Habla Apothecary!"

Ich verstehe kein oxycodone. Parlez vous suppository?

Panthers007
08-30-09, 11:09 PM
Percocet-Pedalers? Vas ist lost?

urbanknight
08-31-09, 09:04 AM
Stop at any garage, even a European one, and ask them to adjust your tire pressure. Give them the desired pressure in Pascals (or Kilopascals if you prefer reasonable size numbers) and see the blank look.
Disregarding your guys' fascinating discussion, anywhere I go where they put air in my tires for me (usually a lube center) they never ask me. They just stick the nozzle there until the hissing stops (many times it's set to 50 or 60 psi), and I drive home feeling mike I have Flinstone tires before I let 20-30 psi out. :mad:

HillRider
08-31-09, 11:10 AM
.... but saying something like Pascals are some nonsensical unit is not really seeing it in terms of the units it is derived from.
Did you actually read what I posted? I never said the Pascal was a nonsensical unit, I said it was an uncommon unit that hasn't caught on in commercial or industrial use.

Noobert
08-31-09, 11:33 AM
700 cm = 22.9658 feet

Myrr21
08-31-09, 05:49 PM
Pressure measurements, for some reason, are still an absolute hodgepodge and horrific to sort out. Off the top of my head:

pascals, psi, bar (which is almost an atm, but not quite), atm, torr, mmHg (same as torr, but people use both)...and I'm sure I've missed some.

Working the the lab, I've seen all of these used in different contexts. I think Pascals haven't won out because they're so small, even if they're sensibly defined; they're just not relevant for most everyday usages.

LarDasse74
08-31-09, 07:07 PM
Did you actually read what I posted? I never said the Pascal was a nonsensical unit, I said it was an uncommon unit that hasn't caught on in commercial or industrial use.

Not for small pressures, but in systems where the pressure and volume are higher MPa (Megapascals) is gaining acceptance. That is a common unit used at my Canadian workplace.

Metric is a far superior measurement system... and becomes stronger with every convert. It is the language that more people in the world speak than any other.

08-31-09, 08:37 PM
Hello!

Someone should've aborted the idiot who created the Metric system. So how big are 700 centimeter tires? I get the impression they are about 27 inchese but my tape measure shows me that 27 inches is about 69 centimeters--27-and-a-half inches is about 70 centimeters, BUT that's still off by a factor of ten. Unless I'm looking at really old-fashioned bikes, with seats several feet from the ground, somehting isn't quite right. From the photos I'm seeing, these are normal-sized bikes. So what's up? One web search seemed as if it suggested 700 centimeters was the WIDTH of the tires, but that would make the tires several FEET wide. Also seems improbable to say the least.

You know, for all the purported virtues of 'simplicity' with the metric system, the traditional measurments are usually much simpler: they were based, roughly, on anatomical or other familiar comparisons, and most folks could use fingers, arms, feet, etcetera to guestimate the approximate size of other objects. (No crude jokes, please).

REALLY big - more than 21 feet in diameter.:roflmao2:

Panthers007
08-31-09, 09:05 PM
Cent is short for centimeter. And for century. It means 100. There are 100 centimeters in a meter. A meter is 39.36 inches. Which is 3.36 inches longer than a yard.

So 700 centimeters = 22.96 feet. Or 7,000 millimeters. Or 275.59 inches.

Confused yet? Good! :thumb:

Jeff Wills
08-31-09, 09:39 PM
700 cm = 22.9658 feet

Judging by this photo, the Imperial measurement system is the work of the devil:
http://www.pezcyclingnews.com/photos/interviews/devil-bike.jpg

une_vitesse
08-31-09, 11:48 PM
except for french and swiss bikes.

une_vitesse
08-31-09, 11:52 PM
There are good reasons for using using inches, as well. If you don't have well calibrated measuring tools, it's easier to accurately halve, quarter, etc. a given measurement than it is to divide it into 10 equal parts. That's one reason why decimal measuring systems had been promoted since the 18th century, but took a while to catch on.

In my line of work, goods are sold by the dozen, which used to really annoy me. Why can't they they sell them in tens? Then, as I gained experience working on different machines used to process these goods, it hit me. It's because 12 has way more denominators. Common variations of said machines can process 1, 2, 4, 6, 8 pieces at a time. Only the first two divide into 10 evenly, where as the first 4 divide into 12. 8 divides in evenly at 24, where it doesn't hit an even 10 'til 40.
brilliant!

7speed
09-03-09, 08:41 PM
I love it when people refer to them as 700 cc wheels.

Wait, no I don't.

Jeff Wills
09-03-09, 11:27 PM
except for french and swiss bikes.

Well, Italian is 36mm x 24tpi. Half-breed!