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How many inches in diameter should I expect on a 700C hybrid bike?

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How many inches in diameter should I expect on a 700C hybrid bike?

Old 09-13-20, 01:25 PM
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How many inches in diameter should I expect on a 700C hybrid bike?

Tire sizes are so confusing. My understanding is that with the tire (a general 35 mm tire), it should approximate about 27.5"???
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Old 09-13-20, 02:25 PM
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Originally Posted by IGH_Only
Tire sizes are so confusing. My understanding is that with the tire (a general 35 mm tire), it should approximate about 27.5"???
Your question is confusing. If you want to replace just a tire and not the entire wheel, replace the tire with another of the same size, in your case another 700c. If you want to get more confused about bike tire sizing (And possibly then become less confused), this is a useful link which gives explanations and tables of various tire sizes.
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Old 09-13-20, 04:24 PM
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Originally Posted by IGH_Only
Tire sizes are so confusing. My understanding is that with the tire (a general 35 mm tire), it should approximate about 27.5"???
27.2441 inches, to be precise. Took about 5 seconds to calculate.

Nothing confusing about it at all. A "700c" rim is 622 diameter; add tire width in mm X 2 = 692mm = 27.2441 inches.
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Old 09-13-20, 05:14 PM
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Originally Posted by badger1
27.2441 inches, to be precise. Took about 5 seconds to calculate.

Nothing confusing about it at all. A "700c" rim is 622 diameter; add tire width in mm X 2 = 692mm = 27.2441 inches.
Thanks, I understood the 622 but I've never seen the formula before and wasn't sure how to calculate how much tire part would add to it.
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Old 09-16-20, 02:07 AM
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Originally Posted by IGH_Only
Thanks, I understood the 622 but I've never seen the formula before and wasn't sure how to calculate how much tire part would add to it.
Tire width and tire height aren't the same thing... tires aren't cylinders. The same tire will have different dimensions when mounted on different rims. Different tires of the same nominal size will have different dimensions when mounted on the same rim. Many tires will not match their nominal dimensions when mounted on any rim.

To get the exact diameter by calculation, you'd need to measure the height of that tire, when mounted and inflated on that rim... at which point you could just measure the wheel diameter directly and skip the math.

What I'm not grokking is what you'd actually need the number for. The only reason I can come up with would be to calculate the circumference, to calibrate a magnetic-sensor bike computer, but that's always been in millimeters?

--Shannon
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Old 09-16-20, 06:18 AM
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Sorry, I'm curious now.............why did this question come to mind? What are you working on that knowing this resolves?
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Old 09-16-20, 09:52 AM
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Originally Posted by burnthesheep
Sorry, I'm curious now.............why did this question come to mind? What are you working on that knowing this resolves?
Me too. Like, where/how does the 27.5" come into play? I thought 700c was also known as a 29'er since it's 29 inches
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Old 09-16-20, 10:07 AM
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Originally Posted by Milton Keynes
Me too. Like, where/how does the 27.5" come into play? I thought 700c was also known as a 29'er since it's 29 inches
It is only 29 inches if a very wide tire (2+inches) is used
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Old 09-16-20, 04:40 PM
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I was just confused much like Milton Keynes because they call it a 29er but it's really not and so forth.
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Old 09-16-20, 09:15 PM
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Originally Posted by Milton Keynes
Me too. Like, where/how does the 27.5" come into play? I thought 700c was also known as a 29'er since it's 29 inches
Originally Posted by IGH_Only
I was just confused much like Milton Keynes because they call it a 29er but it's really not and so forth.
The 'Traditonal' names came from a size designation based on the outside diameter of the wheel/tire. 700A, 700B, and 700C all measured (nominally) 700mm in diameter, with A being the widest tire, and C the narrowest, but they all had different diameter rims, in order for the wheel/tire combination to have a 700mm outside diameter. Same goes for the 26" 'fractional' 3-speed wheels and 26" 'decimal' MTB rims.
Also, countries and individual mfgrs had wheels of different dimensions, but all locally given the same 'size', though none were the same.

Since modern bike manufacturing has really coalesced in the later part of the 20th century, a more common international standard was developed, based on the bead seat diameter (BSD) of the wheel rim (also referred to as ERTO) The 700C size, with it's 622mm BSD became 'the' standard road bike wheel size, so that any tire that fit a 622 rim is referred to a a 700C- ##, regardless of tire width, and overall outside diameter.

'29er' MTB wheels are also 622mm BSD, although usually only the wider offroad oriented tires and rims. (30mm+ rims and 45+mm tires) Narrower road / hybrid stuff is called '700c'

The 29er name was to differentiate it from the older (80s-00s) generation 26" MTBs (559mm BSD)

Confusing things, the "27-five" MTB (584mm BSD) doesn't have anything to do with being twenty-seven and a half inches anywhere, it is just in between the 26er and 29er sizes. It also happens to be the same BSD as the 650B that's starting to make inroads in the gravel / audax segments.


Still don't have a clue as to why the OP question, unless he's trying to Rinko it.
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Old 09-16-20, 09:39 PM
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29 inches is the approximate outside diameter of an approximately 2 inch wide knobby tire mounted on a 700c rim. Fuzzy memory says that the specific tire was the 700c x 50 WTB Nanoraptor, and that they really did measure right about 29 inches. I was working in a shop when 29 started to happen, and as I recall, the reason that they called them "29 inch" instead of "700c" was that MTB wheels were 26 inch, and 700c was the road wheel size, and they didn't want to confuse anyone.

So they decided to confuse everyone.

Then, when the industry decided that MTB wheels should be 650b, they said, "well, 650b is 584 mm, which is in between 26" MTB (559 mm) and 700c (622 mm), and we called 700c "29 inch" when we put it on a mountain bike, so let's split the difference and call 650b "27.5 inch" if the wheel is going on a mountain bike, so that we won't confuse anyone."

Which confused everyone, by taking the original stupid thing that they did, and squaring the stupid.

If the industry had just called them 700c mountain bikes from the beginning, then 650b would have been 650b instead of 27.5" and everybody would know which tires fit which rims on which bikes, and we can't have that.

I often think that there is a meeting that happens every year at Interbike, where the product managers from the bike and parts manufacturers sit down and figure out what the things are that are comprehensible and how to change them to be more confusing. Tire / rim / wheel sizes are so diabolically confusing that it's gotta be intentional... nobody could possibly screw things up this badly by accident.

--Shannon

Last edited by ShannonM; 09-16-20 at 09:45 PM.
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Old 09-16-20, 11:19 PM
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I think the problem is this was posted to General Cycling instead of the Completely Obscure subforum.
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Old 09-16-20, 11:46 PM
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If only they’d do it my way I wouldn’t get to explain about obscure French and British and Schwinn sizes, while failing to mention that American standard wheels are the tire size minus four inches (26-4 inches = 559 mm)
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Old 09-16-20, 11:48 PM
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Measure it with a tape measure? I don't have a hybrid, but 32mm cx tires measure about 27 1/2"- maybe 27 1/4".
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Old 09-17-20, 07:12 AM
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I get that it's kind of like how a 2x4 doesn't actually measure 2 inches by 4 inches.
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Old 09-17-20, 07:39 AM
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Originally Posted by ShannonM
Tire width and tire height aren't the same thing... tires aren't cylinders. The same tire will have different dimensions when mounted on different rims. Different tires of the same nominal size will have different dimensions when mounted on the same rim. Many tires will not match their nominal dimensions when mounted on any rim.
No, a tire isn’t a cylinder. It’s a torus. But for a bicycle tire, the width and height are similar enough to be the same in every practical sense.

To get the exact diameter by calculation, you'd need to measure the height of that tire, when mounted and inflated on that rim... at which point you could just measure the wheel diameter directly and skip the math.
That depends on how “exact” a calculation is needed. Using badger1’s number of 692mm, the size of the tire is 27.2”. If the tire is 1mm taller the diameter is 27.3”. If it is 1mm shorter, it’s still 27.2”. A 10th of an inch isn’t going to cause any real issues with most calculations.

That’s also not taking into account the height difference from loading the wheel which could be substantial and entirely dependent on the pressure used in the tire.
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Old 09-17-20, 08:09 AM
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Originally Posted by ShannonM
29 inches is the approximate outside diameter of an approximately 2 inch wide knobby tire mounted on a 700c rim. Fuzzy memory says that the specific tire was the 700c x 50 WTB Nanoraptor, and that they really did measure right about 29 inches. I was working in a shop when 29 started to happen, and as I recall, the reason that they called them "29 inch" instead of "700c" was that MTB wheels were 26 inch, and 700c was the road wheel size, and they didn't want to confuse anyone.

So they decided to confuse everyone.

Then, when the industry decided that MTB wheels should be 650b, they said, "well, 650b is 584 mm, which is in between 26" MTB (559 mm) and 700c (622 mm), and we called 700c "29 inch" when we put it on a mountain bike, so let's split the difference and call 650b "27.5 inch" if the wheel is going on a mountain bike, so that we won't confuse anyone."

Which confused everyone, by taking the original stupid thing that they did, and squaring the stupid.

If the industry had just called them 700c mountain bikes from the beginning, then 650b would have been 650b instead of 27.5" and everybody would know which tires fit which rims on which bikes, and we can't have that.

I often think that there is a meeting that happens every year at Interbike, where the product managers from the bike and parts manufacturers sit down and figure out what the things are that are comprehensible and how to change them to be more confusing. Tire / rim / wheel sizes are so diabolically confusing that it's gotta be intentional... nobody could possibly screw things up this badly by accident.

--Shannon
It’s actually more confusing than that. The whole lettering designation of the French system is a left over. Wheels with a 650, 650A, 650B and 650C are 4 different sizes of wheels and tires. The point of the letter system was to have wheels the same “size” (outside diameter) with different wheels. A 650 rim (597mm ISO or “Schwinn” size) was meant to be used with narrow tires so that the outside diameter was 650mm. A 650A (590mm or “English 3 speed” size) used a slight wider tire with the same outside diameter. A 650B (584mm) used a 1 1/2 inch tire and a 650C (571) was meant for 2” balloon tires. All 4 were supposed to have the same outside diameter. The 700 system had a similar sizing system. The 700C is about the only thing that survived and it was meant for wide tires...kind of fitting that it’s used for the “29er”.

I’ve been pushing using the ISO size at my co-op classes because of the confusion, especially when it relates to the 27” (630mm) vs 27.5er (584mm) conundrum. Lots of people come in looking for 27.5” tires and want to grab 27” tires off the shelf.
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Old 09-17-20, 08:19 AM
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Originally Posted by Milton Keynes
I get that it's kind of like how a 2x4 doesn't actually measure 2 inches by 4 inches.
More useless information: a 2x4 does...or at least did...measure 2” by 4” in the rough hewn state. All lumber sizes are (well, were) the size of the rough cut from the mill. The rough cut lumber was then planed smooth to the size that you buy from the yard. The sizes have changed more recently...by in my lumber yard days nearly 50 years ago, a “2x4” was 1 3/4 x 3 3/4...as a cost savings device. The trees that are being harvested don’t have as much footage of lumber in them as they used to so they cut down the size to save wood and to get more out of the tree.

Even more useless information: I did a research project with the guy who invented the fast curing glue for finger joints in wood. He was Austrian, survived Stalingrad, survived the Russian prisoner of war camps, and drank vodka like a Russian.
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Old 09-17-20, 03:28 PM
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Originally Posted by cyccommute
It’s actually more confusing than that. The whole lettering designation of the French system is a left over. Wheels with a 650, 650A, 650B and 650C are 4 different sizes of wheels and tires. The point of the letter system was to have wheels the same “size” (outside diameter) with different wheels. A 650 rim (597mm ISO or “Schwinn” size) was meant to be used with narrow tires so that the outside diameter was 650mm. A 650A (590mm or “English 3 speed” size) used a slight wider tire with the same outside diameter. A 650B (584mm) used a 1 1/2 inch tire and a 650C (571) was meant for 2” balloon tires. All 4 were supposed to have the same outside diameter. The 700 system had a similar sizing system. The 700C is about the only thing that survived and it was meant for wide tires...kind of fitting that it’s used for the “29er”.

I’ve been pushing using the ISO size at my co-op classes because of the confusion, especially when it relates to the 27” (630mm) vs 27.5er (584mm) conundrum. Lots of people come in looking for 27.5” tires and want to grab 27” tires off the shelf.
Oh no. You just reminded me that I actually had a Speedster with an English 3-speed sized (590 mm) wheel in the back and regular Schwinn size (597 mm) wheel in the front. I forgot that I ended up with that setup after changing my back wheel for a better one at the Co-Op like, 4 years ago. I just sold that bike right before I moved (about 4 months back). I wonder if the new owner has gotten any flats...
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