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Old 04-23-07, 10:46 PM   #1
bellweatherman
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Is a 26" wheel the same size as 650c?

Little bit confused about the actual wheel diameter of wheels out there. Am I right in that...

700c = 27"
650c = 26"
????
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Old 04-23-07, 10:58 PM   #2
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Incorrect.
700c is about 4mm smaller than 27"
650c is not the same as 26"
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Old 04-23-07, 11:29 PM   #3
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Nevermind everybody. I just did some research on wheel diameter sizes and found the following... Posting this in case someone might find it useful. The number on the left of the "=" is the advertised wheel diameter. The number on the right of the "=" is the true diameter.

From largest to smallest...
27" = 630mm
29" = 622mm
700c = 622mm
650c = 571mm
26" = 559mm (Note: this is for most mountain bike tire. Other 26" tires such as cruiser tires, 1960s, 1970s bikes, etc are different)

I think this is pretty accurate. I have no idea how a 27" wheel is actually bigger in diameter than a 29" wheel. Oh well.
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Old 04-24-07, 12:55 AM   #4
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The left column shows nominal wheel sizes including a "standard" tyre size for the purpose the rim diameter is, or was, intended for. The right column shows rim diameters.

700C = 700 mm diameter when a 39 mm (1.5") tyre is mounted (622 + 39 + 39 = 700 = 28").
29" = 737 mm diameter when a 58 mm (2.3") tyre is mounted (622 + 58 + 58 = 737 = 29").
26" = 660 mm diameter when a 51 mm (2.0") tyre is mounted (559 + 51 + 51 = 660 = 26").
27" = 686 mm diameter when a 28 mm (1.1") tyre is mounted (630 + 28 + 28 = 686 = 27").
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Old 04-24-07, 04:57 PM   #5
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Quote:
Originally Posted by bellweatherman
I have no idea how a 27" wheel is actually bigger in diameter than a 29" wheel. Oh well.
A "29" wheel is basically a wider 700c road rim (ETRTO/ISO 622 mm) used with a wide mountain bike tire and the 29 refers to it's approximate overall outside diameter with the tire mounted, not the rim diameter.

A 27" wheel is a 630 mm rim but used with much narrower tires so the outside diameter is actually smaller than a 29.
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Old 04-24-07, 04:59 PM   #6
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Quote:
Originally Posted by bellweatherman
Little bit confused about the actual wheel diameter of wheels out there. Am I right in that...

700c = 27"
650c = 26"
????
No, they are *all different*, and in fact the inch/millimeter numbers are only vaguely close to the actual size of the rims. It is interesting but fairly useless to try to compare the exact sizes of the rims and tires, since most types of bikes are available only with one wheel size: nearly all road bikes take 700c wheels, nearly all mountain bikes take 26" wheels, nearly all OLD road bikes in the USA take 27" wheels, etc (yes I know there are exceptions).

See Sheldon Brown's tire sizing for the details: http://sheldonbrown.com/tire-sizing.html
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Old 04-24-07, 06:44 PM   #7
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Quote:
Originally Posted by bellweatherman
Little bit confused about the actual wheel diameter of wheels out there. Am I right in that...

700c = 27"
Nope
Quote:
Originally Posted by bellweatherman
650c = 26"
Sorta. There are actually at least 5 DIFFERENT "26 inch" sizes, and 650C is one of them.

I have an article about this at: http://sheldonbrown.com/26

Sheldon "ISO/E.T.R.T.O." Brown
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Old 04-24-07, 07:28 PM   #8
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Quote:
Originally Posted by bellweatherman
Nevermind everybody. I just did some research on wheel diameter sizes and found the following... Posting this in case someone might find it useful. The number on the left of the "=" is the advertised wheel diameter. The number on the right of the "=" is the true diameter.

From largest to smallest...
27" = 630mm
29" = 622mm
700c = 622mm
650c = 571mm
26" = 559mm (Note: this is for most mountain bike tire. Other 26" tires such as cruiser tires, 1960s, 1970s bikes, etc are different)

I think this is pretty accurate. I have no idea how a 27" wheel is actually bigger in diameter than a 29" wheel. Oh well.
Those are bead diameters. The tire can be a lot bigger than the bead diamter
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