Camilo

Apologies in advance for the rant. But read on and I think you'll agree that a rant is somewhat justified.

I've learned to bite my tongue and have come to (BARELY) tolerate, or at least ignore, the now far too ubiquitous and imho irritating and ignorant usage of, for example, "32C" as a tire width descriptor when people are talking about common 700C tires. I understand because that's the way that it's written on tires e.g. "700X32C" and many or most cycling enthusiasts don't even know that the C refers to the rim standard, not the tire width. But, it still perplexes me that so many people think that the "C" somehow refers to the width of the tire, without thinking "what does C refer to anyway?" cm? cc? grade C (i.e. average quality)? There can't be any thought given at all. Anyway, I've stopped trying to correct people because it is just too much. However, I do appreciate it when people do refer to 700c tire sizes as mm, instead of C. My appreciation means nothing, but it's there.

But goodness gracious, cripes all friday, sakes alive, gol durrnit, (sanitized)!!! I'm looking at bicycle articles, supposedly professionally written and bicycle spec lists, again, supposedly written by someone who has a flipping clue. It's bad enough when these "experts" use 32C talking about tire width on 700c wheels. As above, I just roll with it.

BUT, my head explodes when see things like:

... the wide, 650x47c tires roll into and over rocks and roots easily.

I see it far too much - which should be never - in articles and info provided by people who should have a frickin' clue! I want to weep for my country and the world. Please talk me down!

Polaris OBark

Word!

Preach it!

I mark people down on their exams for having wrong units for a living.

This shyte has to stop. Thank you for taking a stand.

HTupolev

Cyclist: "What are good 650mmx47cc 26 inch tire options?"
Salesperson: "Our tire sizing system is working as intended to minimize consumer confusion. The typical human is incapable of comprehending a pair of dimensions."

JohnDThompson 

More to the point, why aren't people using the ISO/ETRTO tire and rim size designations? E.g. "47-584."

BTinNYC 

In a country that rejects the metric system, you have to ask?

JohnDThompson 

The vast majority of tires and rims are made in countries that do use the metric system, yet they persist in marking their products with the archaic and confusing size designations.

Maelochs

Communication is key .... when attempts at communication succeed despite sloppy specifics ... the communication is valid.

pdlamb

Chicken and egg problem. You get rid of the egg -- "My bike tire says 700Cx28 and I need a new one" -- well, all the eggs, but you get the idea. Three to five years later, all the old chickens (new bikes and tires with that label prominent) and the tires and labels say 28-622, perhaps with a small sidewall note that that's equivalent to 700Cx28, and that's what people will ask for. In the meantime, why would you expect manufacturers to swap labels and lose sales because of it?

mstateglfr 

Tires are, at times, advertised as being 'c' width. Its odd, but I figure they are just labeling the tire how they think consumers want/need. Basically, consumers drove them to just label it wrong to make it easier.
Its either that, or the tire brands dont even understand what the designations mean, and I really hope that isnt the case.

shelbyfv

I use mm or just the # when describing a tire but doubt even 25% of cyclists get the distinction. Discouraging but not as bad as then vs than.

Maelochs

I think people realize that "32c" means "32 mm" since no other interpretation makes sense.

If I say "twenty-niner" no body asks "Twenty-nine what?" Even if I say "26x50mm" Most people I know are going to get that it is probably a 650b wheel with a two-inch-wide tire .... and if I say "26x1 3/8" they are going to assume it is whatever the normal cheap 26" standard wheel is which I don't even know ... but somehow, I have always managed to buy the right tires for my bike s for decades, despite not having memorized the correlations between all the various naming standards.
But I can see where engineers and mathematicians might be irked by people misusing units .... or confusing "mass" and "weight" .... or whatever. Oi, the endless sins of the unwashed masses.

Iride01 

If that's the only thing that bothers you then you lead an easy day wading through the stuff here!

When C is seen along side the width number for the size of a tire, it generally means that tire should only be used on a crochet or hook bead rim.

msu2001la

I think very few people in the US can visualize metric measurements and/or assume "c" is some kind of Euro shorthand for CM, or maybe MM.

Maelochs

I am never wrong ... but occasionally I make my stuff more right. (thanks ... )

I think 32 cm is wide enough for most gravel.

(Don't delete the post ... let people wonder what they missed.)

msu2001la

I'm trying to imagine what kind of reaction I'd get if I walked into a bike shop and asked if they had any "47-584" tires.

ClydeClydeson

Wow. Wrong, wrong, and wrong.

• 'C' comes from the obsolete French tire sizing system - there were 700A, B, C and D, where various wheel/tire combos all had a nominal outside diameter of 700mm. A, B and D are long gone so any wheel called 700 will be 700C by default. There is no measurement that fits for a wheel or tire size of 23 or 32 or 38 cm. The 29 inch wheel that seems to be the least confusing is actually a 700C rim. These rims (700C and 29") have a bead seat diameter (BSD, the size the tire must mate with) of 622mm.
• 650b is not called '26' in any modern context. For trekking bikes they are simply called 650b, and for mountain bikes they are called '27.5'. 26 x 50 would almost certainly get you a 26x2.0" tire (old mountain bike standard, superceded by 27.5 (650B) and 29" (700C)). 650B/27.5 have rims with BSD or 584.
• 26 x 1 3/8 refers to one of a couple of obsolete sizes - the most common one is also called 650A, which has a rim with BSD of 590mm. It is not the same as a 'standard' cheap 26" wheel or tire, which is the fading 26" standard of a 559mm rim (see 26x2.0" above).

Result:

0/3, F
but
A- for effort.

prj71

Except that 650b is 27.5 not 26...

msu2001la

I actually think very few people in the US, even among cyclists who pay attention to tire widths, have any idea that 50mm is roughly 2 inches wide.

prj71

As a career engineer for the past 30 years...having to work with both metric and imperial units day to day...I realize 25.4mm = 1"

BTinNYC 

I can think in metric for distances less 24 cm. After that I have to convert. Sadly, I had to convert for radians too.

This 3,900 year old base 12 Babylonian stuff is horrific. Didja know the ancient Babylonian mathematicians quickly gave up on base 12 and moved to base 60 for calculations ...because 60 is divisible by so many numbers its easier to work with.

cyccommute 

+1. If someone were to ask me for a 26x50mm tire, I would hand them a tire for a 559mm rim. If I thought about it, I’d find them a 1.95” width as well since that is closer to 50mm than 2” is.

cyccommute 

Part of the issue is that “650Cx47” just doesn’t roll off the tongue or read properly. Our little monkey brains don’t like the asymmetry of that particular configuration.

Iride01 

Really?

https://blobs.continental-tires.com/...otice-data.pdf

msu2001la

And yet... Continental sells hookless compatible tires that are labeled as 700x32c.
Grand Prix 5000 S TR (continental-tires.com)

They also confusingly list the 700c size as "28". Which is different than the "27.5" size, which they list as 650x32b, which is apparently still unrelated to hooked (crotchet) or hookless, and also means 32-584. Their use of "B" and "C" here also seem to have nothing to do with width, as both tires are the same 32mm width.

cyccommute 

Seems like a post hoc explanation more than what is really happening. If the “C” refers to “crochet” or hooked bead tires, then why does Continental list hookless tires as “700x32C” here? And why do they on the same page under the tab “27.5” list the tires as “650 X 32B”? Last time I checked “B” isn’t an abbreviation for “crochet”. I also can’t seem to find any SI unit that uses “B” as a distance measurement. A 650C rim, by the way, is very different from a 650C using a “C”. The letter designation is in reference to the old French system and has nothing to do with a metric measurement.

The linked article is handwaving at best.