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Confusing tire size

Old 08-17-16, 12:46 PM
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steinrr
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Confusing tire size

I have a tire that has the following markings:

28 x 1 5/8 x 1 3/8 37-622 700x35c

What I don't get is that the "37-622" part says that my tire has width of 37, while the last part (700x35c) says that width is 35. Should not these two numbers be equal? How can a tire be both 37 and 35?

("1 3/8" is close to 35 so I guess that is the correct tire width)

Last edited by steinrr; 08-17-16 at 12:54 PM.
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Old 08-17-16, 12:51 PM
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Do roll out on the tire with it pumped to the PSI you ride with.
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Old 08-17-16, 12:52 PM
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You rather should because the markings and ACTUAL size can vary quite a bit between brands, models etc.
The "contradictory" markings on your tire are rather common.

Don't obsess over a couple MM. Unless you want to adjust the calibration number every few 100 miles to account for tire wear.

IMO, "roll out" tests with the rider on the bike to "flatten" the contact area are a waste.
I think of the tire like a rubber band laying on the table. You can make it "round" or "squashed", but it's still the same length.

Last edited by Bill Kapaun; 08-17-16 at 12:59 PM.
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Old 08-17-16, 12:52 PM
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As I said in my post - I could measure this manually - but that is not the issue here. The issue is why the numbers on the tire seem to say different things...

(I have removed the computer part from my initial post to avoid this becoming the subject...)
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Old 08-17-16, 12:53 PM
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Why worry about it when you could be riding?

You can measure a tire after installing it and the measurements sometime don't match.
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Old 08-17-16, 12:57 PM
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My *computer uses the measured wheel Radius.. some use roll out ... development ,

others there is a scroll thru menu and you just pick , that's close enough.

But, I haven't put a battery in it* for over 15 years.. You really "need " a computer ?
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Old 08-17-16, 01:29 PM
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You're tires have 37mm. 700c x 35c - its not mm, its special sign. Dont see on theyre)))
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Old 08-17-16, 02:02 PM
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Originally Posted by steinrr View Post
As I said in my post - I could measure this manually - but that is not the issue here. The issue is why the numbers on the tire seem to say different things...

(I have removed the computer part from my initial post to avoid this becoming the subject...)
You'd think they'd be the same, huh? It's the fault of the French:

Tire Sizes | Schwalbe North America

French size markings (e.g. 700 x 35C) give the approximate tire outer diameter (700 mm) and width (35 mm). The letter at the end indicates the inner diameter of the tire. In this case, C stands for 622 mm. French size markings are not used for all tire sizes, so, for example, it is not used for MTB sizes.
The C stands for "cul"


Last edited by DiabloScott; 08-17-16 at 02:06 PM.
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Old 08-17-16, 02:17 PM
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DiabloScott:

The table you listed gives me the same headache as my initial question: Why do they print the size in two different systems, where the values does not have the same meaning? Your table also says that 37-622 means tire width 37, while 700x35c means tire width 35. So the confusion remains...
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Old 08-17-16, 02:26 PM
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I'd take a couple of ibuprofen and not worry about it so much. There may be a good reason for the discrepancy -- perhaps the nominal width is 35mm, but ETRTO/ISO wants to list the maximum width (tires always vary a little) to ensure there is clearance.
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Old 08-17-16, 02:29 PM
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Originally Posted by DiabloScott View Post
The C stands for "cul"
It does not.
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Old 08-17-16, 02:32 PM
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You are correct - it is confusing. It is also pretty common. I have seen tires marked 700X38C (40-622) and similar. I always assumed the Iso dimension is measured slightly differently than the French dimension.

But the question is - why does it matter?
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Old 08-17-16, 02:34 PM
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Originally Posted by steinrr View Post
. . . Why do they print the size in two different systems, where the values does not have the same meaning? . . .
Only 37-622 represents values (and then only when mounted on some standard rim). All the others are actually names (ie: nominal).
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Old 08-17-16, 02:43 PM
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Originally Posted by steinrr View Post
DiabloScott:

The table you listed gives me the same headache as my initial question: Why do they print the size in two different systems, where the values does not have the same meaning? Your table also says that 37-622 means tire width 37, while 700x35c means tire width 35. So the confusion remains...
I suspect they're using the ETRTO values as standard, and then using a conversion chart to print the other sizes. It's even more confusing than you realize. For some reason the French 35c is the only one that doesn't match the ETRTO width:

http://biketiresize.com/
47-622 700 x 47C
40-622 700 x 40C
38-622 700 x 38C
37-622 700 x 35C
32-622 700 x 32C
28-622 700 x 28C
25-622 700 x 25C
23-622 700 x 23C

Originally Posted by Wilfred Laurier View Post
It does not.
It's a JOKE, son. French google it. BF censor will *** it out.
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Old 08-17-16, 03:14 PM
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Umm...I assume that Wilfred Laurier is Quebecois....
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Old 08-17-16, 04:30 PM
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Originally Posted by steinrr View Post
I have a tire that has the following markings:

28 x 1 5/8 x 1 3/8 37-622 700x35c

What I don't get is that the "37-622" part says that my tire has width of 37, while the last part (700x35c) says that width is 35. Should not these two numbers be equal? How can a tire be both 37 and 35?

("1 3/8" is close to 35 so I guess that is the correct tire width)
As noted above; the 37-622 is tied to actually measurable values.

The 28 x 1 5/8 x 1 3/8 means that the outer diameter is approximately 28 inches, the tire is approximately 1 3/8 inches wide and 1 5/8 inches tall.

700x35c has lost most of its ties to reality. It is less meaningful than the old USA Automobile tire designations such as: H70-15. 700 originally meant the the outer diameter of the mounted tire was 700mm, and c designated a 622mm BSD rim - no width designation was required, because (700-622)/2 = 39mm wide/tall tire. When people started making wider and narrow tires for the same 622mm BSD rim, everything lost meaning.
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Old 08-17-16, 05:17 PM
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Originally Posted by AlexCyclistRoch View Post
Umm...I assume that Wilfred Laurier is Quebecois....
.. @Wilfred Laurier is a veritable bike forums god. He represents all that is best in us.
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Old 08-18-16, 07:14 AM
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Originally Posted by steinrr View Post
The table you listed gives me the same headache as my initial question: Why do they print the size in two different systems, where the values does not have the same meaning?
You're over-thinking this. The "French" sizing system is deprecated; ignore it. As is the "English" sizing system. Just look at the ETRTO designation (37-622) and be happy.
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Old 08-18-16, 07:16 AM
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Originally Posted by AlexCyclistRoch View Post
Umm...I assume that Wilfred Laurier is Quebecois....
Originally Posted by 3alarmer View Post
.. @Wilfred Laurier is a veritable bike forums god. He represents all that is best in us.
Wrong and wrong.

One of you is pretty close, though.
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Old 08-18-16, 09:47 AM
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Originally Posted by nfmisso View Post
everything lost meaning.
The "C" didn't.
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