Camilo

I ran into an interesting issue on the tire size stated in an online site. Just FWIW, this is a place I have had excellent experience with, and they are on the way to making me happy, so I'm not complaining.

I ordered a set of Vittoria Terreno Dry TNT tires. The web listing said they were "700X37mm". I was assuming that meant 700cX37 (or commonly stated as 700X37c). Turns out the actual tire I received is labeled "700X35C" but also 37-622 on the packaging as well as the tire itself. The 700C label is big and bold as you'd expect, with the ERTO size much smaller, fine print on the tire and package.

The simple question is: Has anyone seen a tire that has a different width for the ERTO (622) spec. vs. the "700C"? Why? Is it a new thing? (although it's not the case for any tires I've ordered in the last year).

No need to read on unless you want the whole confusing story and why I think it is not surprising I was confused....

I understand both the "700C" and the ERTO "622" nomenclature. But every other tire that I have and that I just looked at - about 1/2 dozen different 700C tires in the garage - if they even have an ERTO number, have the same width in both. Customer services says that Vittoria is saying it is actually a 37mm tire. I have no idea if that's true. But why label it 700x35C if they think it's a 37mm tire?

Why do I care? I currently have 700cX36 tires on the bike (which actually measure 36mm) and I wanted to get a tad wider - i.e. 37-38 but not larger than 40. My choices on this site were "37" and "40". 40 would have been OK, but I thought 37 is in the sweet spot I was looking for. Of course this also begs the question, is there a meaningful difference between, say, a tire that measures 35mm and one that measures 36 or even 38mm? Probably not, but I wants what I wants!

Anyway, to go further, the sizes they have listed for this tire in the model "TNT" black sidewall that I'm looking for me include the one I bought, the "700X37mm" and also a "700X40mm". After encountering this confusion in what I received, I looked at the Vittoria website today, and they do not show a 700X37C or 700X40C tire in that model. They do show 700X35C (with the mfgr part number which I received) and also a 700X38C. Well, it turns out that the tire the seller lists as the 40, in the detailed spec (fine print), actually has the manufacturer's P/N for the 700cX38. It didn't even occur to me to verify the tire size with the mfgr part number when I ordered. If I had, I'd have ordered the 38 for sure.

I'm not worried about the company making this right for me. They always have. In fact, I believe they'll ship the new tires tomorrow and give me a return label for the ones I received.

And I kind of understand why the 700X35c is listed as 700X37mm since Vittoria labels the tire with both widths as I wrote above. I'm thinking that the copy writer for the website didn't even think how this would be confusing, using the "ERTO" width in the "700c" spec. Normally - in my experience - they'd be the same anyway. But why choose 37 instead of 35?

Anyway, if you read through my saga, the simple question remains as above: Has anyone seen a tire that has a different width for the ERTO (622) spec. vs. the "700C"? Why? Is it a new thing? (although it's not the case for any tires I've ordered in the last year).

urbanknight

Considering there is no standard for the internal width of the rim which the tire is measured on, this could be a futile quest you're going on.

Camilo

Yeah, you're right - I understand that. Different rim widths produce different actual measured width and there's quite a variation among different rims that people use and the manufacturer certainly can't assume any rim width.

But isn't a given that the two labels, in this case 700cX35 and 37-622 on the same tire, should show the same width, both using 35 or 37? Nobody can assume that a given 700cX35 tire would actually measure 37mm, or 34 or whatever. They don't know, and the user doesn't know until he or she mounts it on the actual rim being used.

urbanknight

Yeah, I have no idea why it would be labeled with two different widths, and I imagine your best shot at getting an answer would be to contact the manufacturer. Even then I wouldn't be surprised if they can't find anyone with the answer.

Kontact 

Look at the sizes in question here:
https://www.michelinman.com/bicycle/...le/conversions

ofajen

ETRTO has standards. They were revised a few years back to recognize that riders were generally running wider rims. At least some if not all manufacturers adjusted tires accordingly. It is, for example, why the GP5000 of a given nominal width runs narrower than a GP4000 of the same nominal width on the same rim.

Otto

KerryIrons

A little confused here. Are you saying it has two different sizes marked on the packaging but the actual tire is marked 37? If that is the case, I would put this down to an error (aka incompetence) in the packaging design department. I would always default to what it says on the tire. And as has been noted, mounted size is the only one that really matters. On my Velocity A23 rims, Continental GP 5000 x 25 tires are 28 mm wide. Another nominal 25 mm tires might mount to a different width, as often gets discussed here. Wear out the tires you've got and get the size you want on the next order. You can manage the size difference by moderating the pressure.

urbanknight

So they actually have standards as to what width rim a tire should be measured on? I was aware that newer tires are being measured on wider rims, but not that there were any sort of industry guidelines.

ofajen

There are standards. There was a significant change at the start of 2020. ETRTO docs are not easy to get without paying a fair chunk but here is a quick summary article on the Vittoria website:

https://www.vittoria.com/ww/en/stori...rto-bike-tires

Otto

Steel Charlie

And Beretta clothing sizes are all one size small compared to the US market ! !

Why can't those Europeans do anything OUR way ! ? ! ?

cyccommute 

Vittoria has done this kind of sizing for a long time, especially when it comes to the 700x35 tires. The ETRTO size has been 622x37 for at least the last 10 years or so.

urbanknight

American companies are into flattering their customers. I wear Levi’s or Wrangler jeans that are labeled 2-4” smaller waist size than I measure on myself.

tyrion

I have seen that but I don't remember where (think is was a Schwalbe tire). IIRC the ERTO width spec is a formal measurement of the bead-to-bead laid flat plugged into a formula, while the "700c x NN" is an informal guesstimation of inflated width.

wolfchild

My Schwalbe Marathon Winter Plus say 42 - 622 and also 700 - 40...The actual measurement after I mounted them on my rims is 42mm wide.

Camilo

On the charts you reference, in the 28" chart, ERTO 622, the "700" number and the "622" number for a given width have the same width. For example, on that chart 35-622 = 700X35C. On my tire, it's 37-622 and 700X35C. See photos.

AH! So my tire is not the only one! I just took a quick look at my Schwalbe Marathon Winter (studded) tires which are about 5-6 years old. They have a lot of sizing labeling on them! But it's all consistent: 35-622 700X35C and 28X1.35

I do understand that the actual width is only determined after mounting and inflating. I'm just curious as I've never seen the labeling like this before.

Quote:

Originally Posted by ofajen

There are standards. There was a significant change at the start of 2020. ETRTO docs are not easy to get without paying a fair chunk but here is a quick summary article on the Vittoria website:

Thanks. This helps

Thanks. I was not aware having not bought Vittoria for I can't remember how long. I've been using mostly Michelin and Continental with a Donnelly thrown in.

No, both the tire itself and the packaging are labeled both 37-622 AND 700X35C - see photos. That's why it's so odd to me. It isn't a huge deal, just a curiosity. But as wolfchild wrote above, evidently it's not unheard of.

Packaging:


Tire:

ofajen

The ETRTO created ISO 5775-1 for tires and 5775-2 for rims. These were in place as early as the late 1990s if not before. This was an effort to create a comprehensive spec for the many tire sizes that existed. The ISO spec of 37-622 is intended to be equivalent to tires with “older markings” of 700 x 35C.

Under the “tires” section of this Wiki you can see a conversion table from ISO 5775 to older markings in inches or millimeters.

https://en.m.wikipedia.org/wiki/ISO_5775

(Not sure why this doesn’t work as a link but you can copy and paste and it works. )

They normally update every five years though the last published version dates to 2014 and the next version is under construction. JIS cooperates with ETRTO on ISO 5775 and has JIS D 9112 and the new version of ISO 5775 will be called ISO/DIS 5775.

Otto

Camilo

Well, kind of a trivial issue for sure. I mean, what is a couple of MMs anyway. I'm not deluded enough to think it's an important factor. I was curious and I appreciate the discussion. I've learned, and am proud that this topic attracted only on-topic helpful responses! Thanks very much all of you

ofajen

Glad if I was of any help. It's a reasonable question since it seems counterintuitive to have different width numbers on the same tire. Good to know that this is just tire manufacturers following the international standard for tire markings. Probably the best they could do given the muddle of conflicting usages over the years.

Otto

wolfchild

It will be interesting to see what they measure once mounted on the rims...Some tires such as Continentals and Maxxis can run 3mm smaller than what they claim on the label.

ofajen

Under the current ETRTO standards, a tire of 35 or 37mm nominal width is expected to be mounted on a 23C rim. It’s still quite common for these tires to be mounted on narrower rims and the tire section will be narrower by perhaps that much.

I wouldn’t hesitate to run a tire like that on a 17C rim, but it will make it less than the nominal width, especially since I’ll be running it around 50 psi or so on crushed stone.

Otto

wolfchild

What I am talking about has nothing to do with rims. Some brands of tires just run smaller than claimed no matter what type of rims you mount them on. It's just the way that they are manufactured. I've had several different brands of tires over the years in the same size mounted on the same sized rims and the sizing was inconsistent among the different brands.

Camilo

That's been my experience - that most tires measure a bit smaller than labeled on the rims I use, a couple are maybe a mm wider, but not anything significant.

With these particular wheels on my gravel bike, they're not as wide as what might be considered normal for "gravel" bikes these days. They are Boyd Altamont with an inner width of 21mm. They are unlikely to produce any additional width when mounted and that's been my experience so far with the tires that are on them (Donnelly MSO: 36mm labeled, ~35 to 35.5 measured). No big deal, just what I'm keeping in mind when I choose tire size.

On the other hand, my 650b wheels have Race Face ARC25 rims that have a 25mm inner width which do result in wider than spec'd tire. I was pleasantly surprised that the Maxxis Rambler 47mm tires I mounted on them (to stay on topic: labeled both 650X47b and 47-584) plumped up to 49-50mm, which is close to as wide as I can get in this frameset.

FWIW, the Altamonts are great for what I wanted for these wheels, versatile enough for a bike that is often the only bike I have when I travel with the travel trailer. I could, if I was inclined, mount something as small as a 25mm if I wanted to and as large as 44mm which is the stated max for 700C wheels on this frame. So they're right in the sweet spot for this size (35-40mm) tire. But again, I would not expect the tires to exceed the labeled width in practice.

Before I got the current frameset (Lynskey GR300) I used a cross bike with rim brakes for this kind of riding, and just used the road wheels I had on hand. It's been a while since I measured, but they're in that 17mm or so ball park. I mounted the same Donnelly MSO 36mm tires with no issues whatsoever for several years. They measured just a bit smaller, 35mm IRC.

smd4

My Veloflex Master 23s say only that on the tires themselves. They measure 23.1mm on the rim. Box says 23-622.

Below that is written “Use only on rims standard E.T.R.T.O. 622x13c/15c.”

PeteHski

It's just that different brands haven't all accounted for the same rim width. We're in a state of flux at the moment where tyre brands are moving toward quoting tyre widths on wider rims. But they are not all on the same page yet, so you might get one tyre width quoted for say 17 mm rims and another (sometimes even the same brand) with a width quoted for 23 mm rims. Pirelli even provide a chart with tyre width vs rim width and the labelled width is just quoted at a particular rim width - I can't remember what rim width that actually was. But I'm sure you get the idea.

Until every brand labels their tyre widths based on the same rim width, there are going to be differences between brands when you fit the same labelled width onto your own rims.