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Hello everybody. It's Peter Kaltreider at SIXTHREEZERO bicycles. We get a lot of questions about how to find the right bike-size tire for your bike. So we'll get into that. Stay tuned.
I brought out a two-by-four here to illustrate some common misconceptions about bike tire sizing. I'm going to keep it very simple because it is actually a very simple topic. However, a lot of our customers sometimes go down the Google wormhole in the wrong direction and kind of get confused and make it more complicated than it needs to be. Nate, can you come in here really quickly? Most people know this, I think a lot of folks don't. We call this a two by four because it used to be two inches by four inches. But as you can see, a modern two by four is only three and a half inches by one and a half inches. So the two by four sizing is not really a size. It's just a nominal name. It's also called a stud.
Anyway, I know that everyone's going to make a lot of stud comments in the YouTube comments at my expense. Just if you do, try and be original because that's rare. Okay. Oh, I'm going to keep my measuring tape because I want to show you guys something else. However, let's get to the easy part. The sizing of your tire is super easy. It's right on the tire. Okay. So just come right on in here, Nate, I'm going to show you, there are actually two sizes here. The one you're looking for is the 26 by 2.125 right here. Okay. This is inches by inches. Now, this is kind of like the two by four. It's not exactly that. The way that a tire is actually measured is more precisely if you're a tire or a wheel manufacturer, which I don't think any of our customers are, is actually this number right here.
The 57-559. This is 57 millimeters, which is supposed to be the width of the tire by 559 millimeters, which is supposed to be the bead seat diameter. Again, we're getting way too complicated. I just wanted you to remember that this is the number you're looking for here. Just the regular inches. Okay. The bead seed diameter is right here. It's roughly equivalent to the bead of the tire right here measured in millimeters. I don't have a metric ruler, but this is what you'd be measuring from. Basically the bead to the bead. I don't know why you would need that measurement unless you actually are a wheel or tire manufacturer or are restoring a vintage bike for which you don't have a tire to reference. Now, let me show you the size of a racing wheel. I'm going to show you this because bicycle tires are measured in three different ways.
They're measured in metric with millimeters, or they're also measured with inches, but there are two types of ways they're measured with inches. Some are inches with decimals, such as the 26 by 2.125 or say 26 by 1.75. They can also be measured in fractions, 26 by three quarters instead of 26, by 1.75. These three ways metric, inches with decimals, or inches with fractions, none of these are interchangeable. So you cannot go into Google and just use your Google conversion and figure that out. If you really want to get precise, you can use the ISO number, which is this. But really what you should do is just reference the tire that you already have, or go into a bike shop because here's the thing. If you try and do the conversion, which is possible, you can do the conversion in Google.
You're going to find the wrong tire size and you're going to break your face because this is not the real size. It's really just a name like Jack or Nancy. In fact, I think that they should name tires like they name hurricanes. It'd be less confusing. One last thing, a lot of our customers ask us about what is the ERTRO number. Okay. If you find this number, can you please let me know in the comments where you're finding that information? Because we get this question pretty regularly and I still haven't figured out exactly, but ERTRO is the European rim and tire. I'm sorry, the European Tire and Rim Technical Organization and entire spelled with a Y. So it really doesn't apply to us at all, except that they do share the same standardization with the ISO.
ISO is actually the International Organization of Standardization, which is IOS, but it's called ISO. And that's this number right here. Again, I don't really know why you would ever really need that number. You should just use the name right here, the 26 by 2.125. It's super simple. Keep it simple. Don't try and mix and match any fractions or decimals or metrics. Nate, did we catch this one with the millimeters? So this one sometimes you'll see this also on hybrid electric bikes, e-bikes is a metric system where for instance, this is a 700 by 23C. This is a common size of 700 for hybrid bikes, but you'll see a wider tire. It won't be 23 like for a racing tire, it'll be more like 38 millimeters. Again, it's kind of nominal. It's not the actual size. The actual size again will be the ISO over here, 23 wide by 622.
Now you can see the 23's are the same because of the tire width, however, the diameters are different because the 700 is measuring kind of the outside. Looks like measuring a balloon. It's not super precise. So what they do is they actually measure the bead seed diameter. We're not going to get into that. It's too complicated and you don't need it unless you are restoring a vintage bicycle or you are in the wheel or tire manufacturing business. I hope that that cleared everything up. All right, thanks for watching. I really hope that was helpful. If you need any more help, please don't hesitate to contact us at 310-982-2877 or the team at sixthreezero.com. SIXTHREEZERO is spelled out S-I-X-T-H-R-E-E-Z-E-R-O. Also, subscribe to our channel and remember, it's your journey, your experience. Enjoy the ride.
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