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Old 05-21-07, 01:58 AM   #1
DVC45
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So, what happened to 27" wheel? Why 700c for road bike's?

I can't help but notice that the 700c's seems to be the most popular, if not the standard for road bikes. I'm just wondering why is this so? What pushed the 27" wheels to (almost) obscurity? Is there any inherent weakness/disadvantage on 27" wheels?
Thanks in advance!
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Old 05-21-07, 03:19 AM   #2
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Originally Posted by DVC45
What pushed the 27" wheels to (almost) obscurity? Is there any inherent weakness/disadvantage on 27" wheels?
Thanks in advance!

You have to figger, the only reason bike manufacturers went to 27" in the first place was for the american market back in the "bike boom" days. Back in those days "metric" was a curse word and it confused too many people trying to figure out what 700 centimeters was. So they went to the next higher american standard measure size, to an even 27-inch (about 4mm bigger). As far as inherent weaknesses or disadvantages, there were none. They were actually pretty strong, but all the higher end bikes, like from europe, stayed at 700c, and the mass produced "bike boom" bikes, which were low to medium grade bikes mostly, for the american market, went to 27-inch for their larger adult bikes.

Over the years I had lots of 27-inch bikes, and they were all good bikes, but they were'nt on the same level as a Colnago or a Tommasini. All the cutting edge racing development in wheels, rims, etc, were all based on 700c anyway. All the higher end european frames with a racing pedigree were all built for 700c and they kept it that way.
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Old 05-21-07, 07:00 AM   #3
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I think you've got it a bit backwards. 27" is actually a bit smaller than 700c; 630 to be exact.

http://www.sheldonbrown.com/harris/tires/630.html
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Old 05-21-07, 07:48 AM   #4
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Originally Posted by skiahh
I think you've got it a bit backwards. 27" is actually a bit smaller than 700c; 630 to be exact.

http://www.sheldonbrown.com/harris/tires/630.html
You are partially correct. A 27" wheel does have a bead seat diameter (BSD) of 630mm. A 700c wheel has a BSD of 622 mm, so a 27" wheel is actually 8mm larger in diameter than a 700c. 26" mountain bike wheels have a BSD of 559mm, so they are 63mm smaller than a 700c (almost 2.5"). The reason for these oddities is that wheel sizes were the outside diameter WITH A TIRE MOUNTED. Only accurate for one tire size, and can be confusing as anything, but the way it was done. It is often easier to just use the BSD measurement.

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Old 05-21-07, 07:49 AM   #5
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700c is 622mm.
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Old 05-21-07, 09:47 AM   #6
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27" was a popular rim size for wired-on (clincher) tires used on sport touring and touring bikes before and during the early seventies bike boom in U.S. People wanting to race used tubulars whose rims were the same as 700c. If you went out and bought a racing bike but got tired of the extra work involved in tubular ownership you got a new set of wheels with 700c clincher rims. Although it is sometimes easy to fit a 700c wheel on a bike built for a 27" rim by adjusting the brake pads; it's often more difficult to stuff a 27" rim on a bike built for tubulars or 700c clinchers.

It wasn't difficult for bike manufacturers to standardize on 700c. By the 1980's nicer clincher tires were being made and clincher rims with hook edges were available to allow high pressure tires for the racing crowd.

The unfortunate development is that bike manufacturers have shrunk the available clearance in the fork and brake areas of modern bikes such that only very skinny very high pressure tires will fit. And there is no room for fenders. A lot of versatility has been lost.
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Old 05-21-07, 12:01 PM   #7
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Originally Posted by MKahrl
27" was a popular rim size for wired-on (clincher) tires used on sport touring and touring bikes before and during the early seventies bike boom in U.S. People wanting to race used tubulars whose rims were the same as 700c. If you went out and bought a racing bike but got tired of the extra work involved in tubular ownership you got a new set of wheels with 700c clincher rims. Although it is sometimes easy to fit a 700c wheel on a bike built for a 27" rim by adjusting the brake pads; it's often more difficult to stuff a 27" rim on a bike built for tubulars or 700c clinchers.

It wasn't difficult for bike manufacturers to standardize on 700c. By the 1980's nicer clincher tires were being made and clincher rims with hook edges were available to allow high pressure tires for the racing crowd.

The unfortunate development is that bike manufacturers have shrunk the available clearance in the fork and brake areas of modern bikes such that only very skinny very high pressure tires will fit. And there is no room for fenders. A lot of versatility has been lost.
How true -- and I would guess most recreational cyclists aren't aware of the limitations when they make their new purchase.
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Old 05-21-07, 12:57 PM   #8
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So, the 27" demise was a victim of metric standardization of European bikes, and Europeans being in the forefront of racing back in the day. If Mr. Armstrong was racing then, I would guess, the 27" wheels would have been the standard of choice.
Thanks for the education guys!

Last edited by DVC45; 05-21-07 at 06:33 PM.
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Old 05-21-07, 02:11 PM   #9
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Originally Posted by nemonis
You are partially correct. A 27" wheel does have a bead seat diameter (BSD) of 630mm. A 700c wheel has a BSD of 622 mm, so a 27" wheel is actually 8mm larger in diameter than a 700c. 26" mountain bike wheels have a BSD of 559mm, so they are 63mm smaller than a 700c (almost 2.5"). The reason for these oddities is that wheel sizes were the outside diameter WITH A TIRE MOUNTED. Only accurate for one tire size, and can be confusing as anything, but the way it was done. It is often easier to just use the BSD measurement.

God bless!
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ugh... my head hurts now!
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Old 05-21-07, 06:23 PM   #10
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Quote:
Originally Posted by nemonis
You are partially correct. A 27" wheel does have a bead seat diameter (BSD) of 630mm. A 700c wheel has a BSD of 622 mm, so a 27" wheel is actually 8mm larger in diameter than a 700c. 26" mountain bike wheels have a BSD of 559mm, so they are 63mm smaller than a 700c (almost 2.5"). The reason for these oddities is that wheel sizes were the outside diameter WITH A TIRE MOUNTED. Only accurate for one tire size, and can be confusing as anything, but the way it was done. It is often easier to just use the BSD measurement.

God bless!
Wayne J.
That so called BSD is called ERTO and ISO within the industry. Avoid talking about 26" wheels, as there are 4 different ones and 6 different 24" and 3 different 20". Read the numbers in parthenosis next to the tire size on the tire to get the ERTO of your current tire before buying a new one.
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Old 05-22-07, 06:37 PM   #11
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27" is better for fixed-gear riders because of its larger diameter wheel, which translate into higher pedal clearance for making sharp turns.
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Old 05-22-07, 07:33 PM   #12
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as a former mechanic i avoided 27inch wheels after a while the boss phased them out of the shop
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Old 05-22-07, 08:12 PM   #13
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27" is better for fixed-gear riders because of its larger diameter wheel, which translate into higher pedal clearance for making sharp turns.
27" is not better if you have a fixed gear frame that was designed for 700c wheels.
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Old 05-22-07, 08:15 PM   #14
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Originally Posted by DieselDan
That so called BSD is called ERTO and ISO within the industry. Avoid talking about 26" wheels, as there are 4 different ones and 6 different 24" and 3 different 20". Read the numbers in parthenosis next to the tire size on the tire to get the ERTO of your current tire before buying a new one.
Although that might be technically correct, there IS a standard 26" wheel and that is the one that is 559mm. Pretty much every mountain bike out there has that size. (Which confuses the crap out of people when they try to mount a new tire to an old "26 x 1 3/8" rim).
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Old 05-22-07, 08:47 PM   #15
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Originally Posted by Thor29
Although that might be technically correct, there IS a standard 26" wheel and that is the one that is 559mm. Pretty much every mountain bike out there has that size. (Which confuses the crap out of people when they try to mount a new tire to an old "26 x 1 3/8" rim).
Yup! That happened to me when I bought a 26" tires from Walmart for my friend's vintage bike. The old, worn out tires say's 26" something, but the new tires just won't fit. I finally went to my LBS and they gave me the right tires.
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Old 05-23-07, 02:46 PM   #16
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A lot of middle- and higher-end bikes sold in the US for touring even into the 1980s used 27" wheels because if you destroyed a tire in the middle of nowhere you could get a replacement in Smalltown, USA.
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Old 05-23-07, 08:35 PM   #17
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A lot of middle- and higher-end bikes sold in the US for touring even into the 1980s used 27" wheels because if you destroyed a tire in the middle of nowhere you could get a replacement in Smalltown, USA.
I think that would still be true today, since Walmart still carries 27" tires, given, of course, the smalltown has a Walmart nearby.
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Old 05-23-07, 09:22 PM   #18
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I think that would still be true today, since Walmart still carries 27" tires, given, of course, the smalltown has a Walmart nearby.
A well stocked ACE Hardware would have 27" tires too. You can still get touring frames and forks with clearance for 27" wheels from custom builders.
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Old 05-24-07, 12:29 AM   #19
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Originally Posted by DVC45
So, the 27" demise was a victim of metric standardization of European bikes, and Europeans being in the forefront of racing back in the day. If Mr. Armstrong was racing then, I would guess, the 27" wheels would have been the standard of choice.
Thanks for the education guys!
I think it's more the case that the metric system is inherently more rational than the english system.
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Old 05-24-07, 04:21 AM   #20
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Originally Posted by Thor29
Although that might be technically correct, there IS a standard 26" wheel and that is the one that is 559mm. Pretty much every mountain bike out there has that size. (Which confuses the crap out of people when they try to mount a new tire to an old "26 x 1 3/8" rim).
"Standard" for mountain bikes. Millions of American and English 3 speed bikes were sold with standard 26 x 1 3/8" (590 mm) tires.
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Old 05-24-07, 06:08 AM   #21
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Originally Posted by skiahh
I think you've got it a bit backwards. 27" is actually a bit smaller than 700c; 630 to be exact.
I measured from the floor to the top of the wheels on my two bikes. The 27" wheels with tire are more than an inch bigger than my 700C wheels with tire.
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Old 05-24-07, 01:05 PM   #22
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You have to figger, the only reason bike manufacturers went to 27" in the first place was for the american market back in the "bike boom" days. Back in those days "metric" was a curse word and it confused too many people trying to figure out what 700 centimeters was.
I'm not sure if this has been mentioned already, but the "c" DOES NOT MEAN CENTIMETERS. That wheel would be about 23 feet in diameter! "700" is the nominal diameter in millimeters, and the letters A-D originally designated the width of the rim. For some reason, we still use the "700" and "c" even though they have no literal meaning.

proof: Sheldon
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Old 05-24-07, 02:00 PM   #23
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I still run 27" on my touring bike for the very reason stated, that I can get a 27" tire literally almost anywhere!
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Old 05-24-07, 02:49 PM   #24
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Originally Posted by DVC45
I think that would still be true today, since Walmart still carries 27" tires, given, of course, the smalltown has a Walmart nearby.
The difference now, I suspect, is that 700C tires are more readily available than they used to be.
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Old 05-24-07, 03:17 PM   #25
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Originally Posted by twobikes
I measured from the floor to the top of the wheels on my two bikes. The 27" wheels with tire are more than an inch bigger than my 700C wheels with tire.
As far as which tire will fit which rim, the outside diameter of the tire is irrevelant, other than the issue of rim width/tire width, which is a whole 'nuther matter (fatter tires are generally wider tires, etc.). 29" mountain bike wheels are actually 700c rims with fat mountain bike knobbies on them, for example, and the outside diameter of the inflated tires will usually be in the close vicinity of 29," hence the name. But the bead seat diameter of the rim is exactly the same as a road rim designed for ultra-skinny 700c road tires. I've got a friend with a 29" mountain bike, she uses 29" x 2.2" knobby tires on the bike for off road riding, and 700 x 32c slick tires for road riding. Quite a difference in the outside diameter of the tires (at least 2" I'd say), but the same rims for both.

27" rims have a bead seat diameter of 630mm, 8mm larger bead seat diameter than 700c rims, which have a bead seat diameter of 622mm. If you have two tires with identical sidewall heights, and one is a 700c tire and the other a 27," then yes, the 27" will have a slightly larger outside diameter.

Inner tubes are interchangeable for the two sizes, as long as you take into account the width range. The tubes these days are usually marked 700c, but they're plenty stretchy enough to put on the slightly larger diameter 27" size without it making a difference-

Last edited by well biked; 05-25-07 at 10:31 AM.
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