I don't want to fuel the conspiracy theories, but has anyone considered that part of the reason it takes so long might be related to parity.
Consider,
a liter is slightly more than a quart, you think the dairy, and beverage folks want to change
a meter is slightly more than a yard, great for the carpet folks,
a kilo, slightly more than 2 pounds, etc.

In a world where a pound of coffee has been downsized to 11.5 oz, and one ice cream maker now sells 14oz "pints" does anyone doubt that we'd be 100% metric if the relative sizes were reversed?

I would think walmart could sell a lot of metric scales... many of their customers would be excited to see a number less than "300" on a scale!

(joke made by someone close to the 300 lb mark himself)

Pshaw! Go big! (36" wheel SS mountain bike) :
http://1.bp.blogspot.com/_Fg9xrCe_jx...Sheep_36er.jpg

You buy pounds of coffee that only weigh 11.5 oz? Francis, WTF? Haven't seen that 14oz pint, either (but ice cream isn't really about volume except from a marketing viewpoint...weigh your ice cream, the less overrun the better).

Interesting thoughts about metric, pains me every day to still see us using the English system when most of the world doesn't....as I deal in int'l logistics and pounds are pretty much just US stuff in the freight world. Didn't really change pricing except for maybe fleecing dumb Amurricans that couldn't convert...

Yeah, the short ice creams have been out for quite a while. I've only noticed the 1 gal. and half gal. downgrades, but they're practically industry wide, now.

Just a couple of weeks ago I noticed Tropicana is slinging 59oz "half gallons" of juice! You gotta watch those sneaky bastidges.

They don't call 'em half gallons of course, but you just kinda think they are when you see a carton that size.

Oh, and of course there's an even greater abomination. Short pints of beer! Just say no.
http://honestpintproject.org/

That's just dishonesty and will always exist. The real abomination are those 330-340 mL beer bottles.

The teaching of New Match and the metric system were totally unrelated.

I believe the market came to view 700c as having a higher "cool" factor, because that was the size the racers used. It became slightly unfashionable to have 27" tires.
Since so many cyclists are gear-junkies, 700c wheels became part of an "essential components" group.
I have examples of both, and find more difference as a result of tire WIDTH than from the 8mm difference in diameter.

good old ISO standard TEU containers.

If you've noticed, 650B is entusiastically promoted in the USA by a few places (Pacenti, Rivendell, BQ) that own special 650B tire molds and retail/wholesale tires in that relatively rare size - NTTAWWT.

Interestly, Grant Petersen of Rivendell did propose creating a new tire/wheel size a few years ago: ISO603. I think some of the faithful organized an intervention.

that's an interesting size....
glad it never materialized.

Of course not, I buy coffee in bulk and get what I pay for. My point was about the prepackaged quantities. Almost everywhere you turn products are being downsized, for decades coffee came 1# to a can, then it was 13oz, now it's 11.5 oz with some brands. So far only one company has downsized their ice cream containers (in the US ice cream is sold by volume, so makers can lower cost by whipping more air into it) but with competitive pressure, others are sure to follow.

Competition makes it difficult to raise prices, so manufacturers find it easier to lower size or quality, and hope no one notices, or cares enough to try another brand. It's interesting that the liquor industry was quick to adopt, but that's product shipped globally, though 750ml, is smaller than the old US standard of 4/5 quart.

BTW- I agree that lots of wheel size changes are introduced mainly to creating something for marketing to talk about, but the move to 700s wasn't an introduction of a new size, it was the elimination of an old redundant size. It isn't reasonable to support the diversity of product we enjoy in the bike world, duplicated in 2 standards only 1.3% different in diameter.

Does Ireland count as strange? On my tour earlier this month in western Ireland, riding a Bike Friday New World Tourist, I had tire problems and had a hard time finding an appropriate 406 tire. Plenty of BMX tires but not many that were narrow enough to fit without rubbing the chainstays. In fact I had to take a knife to some of the knobs.

The ISO are my heros. You know what ISO actually stands for? It's the International Organization for Standardization. They decided that it would be to confusing having a different name in every language, so they standardized it.

Interesting thread, interesting question. I'm going to add a little info, it's been touched on but not specifically noted. It is classic market economics, on supply and demand sides. You'll have noted a lot of the answers cover aspects of the changing demand over time. But only a small note of the changes for the producers. In the 60's almost all bicycle supply lines were still nationally based. US made bikes sold in the US. Mexican bikes sold in Mexico, Spain-Spanish, Italy -- but you get the idea. In the late 60's and on, globalization started - as noted on the demand side in previous posts. But manufacturers also started producing for, and in, global markets. Production went overseas. So, when 700c became popular (style preference) in the US, producers eventually jumped on it and dropped 27", in order to gain efficiency. As economists would say, this was a productivity improvement - it could save money throughout the whole supply chain. Shipping was simplified. Inventory was simplified. Your LBS gained profitability, since they no longer had to buy and stock 2 sizes of everything. Didn't happen overnight, and it was pennies at a time, of course, but it happened.

As for Mexico still having 27" wheels, I don't know if this is still true, but it could also have a production side reasoning. Due to its cheap, yet highly trainable labor market, and convenient location near major raw supplies, Mexico has long been a bicycle producer. It was ramping up bicycle production when the US was ramping down. They could have been among the producers that bought the 27" production line equipment. So, old Chicago Schwinn production line stuff might still be alive and well in Matamoros. That Mexico is still a bicycle producer for their own market also means they don't have the producer motivation to change to 700c. And, on the demand side, their internal market is not as strong as that in the US. Their populace doesn't have the spending power to buy a fancy bike just 'cause they want to improve their tri-time at this fall's local tri-meet. Small high-end market, and like an earlier poster said - the low end demand doesn't care about wheel size.

As for why 27" happened in the first place (which is another excellent question!), didn't we get that size from the English bicycle imports? I need to go check what Sheldon has to say about that. Or there might be an old post in the rec.bicycles.misc archives.

Do you really need that much juice?

Because a 700c and 27" are both road tires and therefore, not that different, while a 26" is a MTB tire and usually knobbed. ;-)

700c, ISO622, can also be 29'er, and this size has a tire selection from 19mm to 62mm wide.

I was burned recently by all these tire size differences. My daughters road bike tires were labelled 24" diameter. "easy" i figured, so I went down to walmart to buy a replacement 24" tire. Tried to mount it and it didnt fit - too small for the rim. I checked Sheldons site and found out that apparently there is a juvenile size wheel diameter that is 540 iso. However, the tires are marked 24". It so happens that this old french / juvenile size is the same rim that is used in some wheelchair applications. The "common" 24" walmart tire is 507 iso.

This bike / wheelset is only 3 years old (GMC brand sold on Amazon), but when it comes time to change the tires, Ill be surfing wheelchair sites for tires. I never new there was a juvenile size for road bikes. At least Ill be able to fit wheelchair tires. I think it would be impossible to find this tire anywhere else.

there's actually 3 different 24" sizes.
507, 520 and 540.

The 26"/559 tires I've bought in the last 2-3 years for a tandem and two recumbents have all been 'road' tires, more or less - most definitely not MTB tires.

Older British club and sport bicycles were fitted with a 597mm wheel and a 26 by 1 1/4 tyre... Dunlop was the chief supplier of these and rims were available in chromed steel, stainless, and aluminum (uncommon). Dunlop stopped making tyres in this size after they realized they made more money selling car tyres and for a time it was very hard to get a decent, high performance tyre in this size.

In the early fifties you could buy some English bikes with 27inch wheels although the 26 by 1 1/4 was the most popular and by 1956 - 57 the 27 inch wheel had replaced the 26 by 1 1/4 wheel as standard.

The British also used the 28 inch over sized rim and tyre which has a 635mm rim and is marked as being a 28 by 1 1/2 while the European and Canadian 28 inch is really a very wide and deep 622, which is the same rim size used on 29'r mountain bikes.

The modern Pashley Guvnor uses the 635 wheel and oversized tyre.

The now common 559 / 26 inch mtb rim and tyre was taken from Schwinn.

Smaller riders can have issues with larger wheel sizes as this can cause serious toe overlap so many very small race bikes are fitted with smaller 650c / 571 or high performance 26 / 559 wheels.

Yeah and I get asked all the time why there aren't more 53 foot containers, too. At least TEUs account for 20s and 40s.