Adventures in Unusual Wheel Sizes

In this modern era the choice for wheels/tires has pretty much been limited to two sizes: 26 inch and 700C. Pretty much 99% of bikes meant for adults you'll see in stores will be one or the other. 26 inch (bead seat diameter of 559mm) is the standard for mountain bikes and cruisers. 700C (b.s.d 622mm) is the standard for road bikes and hybrid/comfort bikes. That's pretty much it.

But that of course hasn't always been the case. There are plenty of other sizes that have been used for adult bikes over the years. A run-down of some of the most common oddball sizes, from largest to smallest:

• 28 inch (635mm): Used for olden rod-brake roadsters in the UK and Europe
• 27 inch (630mm): Commonly found on road bikes (aka "10-speed") in the 70's and 80's
• 26" x 1 3/8" (590mm): Found on most British three-speeds and some American adult utility bikes, three-speeds, and low-end ten-speeds up until the 1980's. Both of my British bikes use this size wheel, and if you've read my blog long enough, you know that I like this particular size. Also known as EA3 or 650A.
• 650B (584mm): This size is very much French, as French sizing is all number-number-number-letter. Commonly found on older French touring and utility bikes. Once considered dead like Latin, this size is making a big comeback and has its share of fans. (If you want to look cool at any randonneuring event, mention how you're getting a custom bike with "low trail" and 650B wheels. If the conditions are right, you just might get laid.)

While all of the above sizes are uncommon, they are still common enough that you can find tires and rims for these wheels. 27" and 26" x 1 3/8" tires and tubes can be found in any Wally World in this great nation.

But there's plenty of other sizes out there, so when I encounter them out in the wild, I take notice.

I spotted this bike last week:

From a distance you can tell it's small. But how small, you ask? Well, I didn't measure the frame size but I saw the size of the wheel: 24" x 1 3/8". Now a 24 inch wheel isn't super-rare by itself. It was a common "juvenile" wheel size for kids too big for 20 inch wheels and too small for 26/27. My first ten-speed was a 24" Huffy that I got around 1986. But this size pretty much faded away for the most part in the modern era. (Sheldon Brown blames the death of the 24 inch size on "wheelie" bikes.) But as there is more than one 20" and more than one 26" size, there are multiple size that fall under the 24" banner. These are the ones I could find via Sheldon Brown:

• 507mm (24" x 1.5"-2.125"): Juvenile mountain bike and cruiser. I'm guessing this is the most common one.
• 520mm (24" x 1"): High performance 24. Used by Terry.
• 540mm (26" x 1 3/8") Juvenile road bike size used in the UK and Europe. Also known as 600A.
• 547mm (24' x 1 1/4" or 26" x 1 3/8" Schwinn.) Looks like it was mostly a Schwinn size, because Schwinn was notorious for doing wheel sizes just slightly different. In Schwinn sizing it's also known as a S-5.

The 540mm size of the Fuji bike above looks to be the least common of the above, at least in the States. I couldn't find any tires for this size through Bike Tires Direct, so that can explain why the tires on this bike are so beat. Though 540mm looks to be a common wheelchair size, so they can always use those if they're compatible?

Onward, friends. A couple days ago by the library I ran into a pile of free bike parts on the sidewalk. I always check these out. There were two wheels that looked 26 inch, and the rear one had a Sturmey-Archer AW three-speed hub, dated 1959! You bet I took it! I might be able to use the hub for something else. But the wheel size looked pretty odd to me. 26" x 1 3/4". I took it home and looked it up on Saint Sheldon's site.

Turns out this is quite the oddball size. There are five 26 inch sizes. Sheldon says that while 1.75" and 1 3/4" may look like its the same size, because one is "spelled out" in decimal form, the other fractional, it means that they are not the same size. 1.75" would make it the common 26" size (559mm), the 1 3/4" means it's something else. It's 571mm wide. While 571mm is the same size theoretically as the 650C used on some triathalon bikes, the widths of the two wheels are radicially different. The 26" x 1 3/4" is once again a Schwinn-specific size. Oh, Schwinn! You American behemoth that refused to follow any sort of industry standard in wheel sizing, insisting on going your own way because you could. This size was known by Schwinn as the S-7 (they really like the S-number scheme). Tires are still available because it's Schwinn (they used it on their middle-weight bikes) but you're pretty much limited to a selection of one tire, just like with their 597mm/26" x 1 3/8"/S6** A choice of one, sooooo American! 

Yes, I love nerding out about tire sizes.

*Not to be confused with the more common "British" 26" x 1 3/8" (590mm)

**Not only was Schwinn contrary in the sizes they used, they were contrary in their sizing. Wouldn't it make more sense if the numbers went up in correspondence to the larger sizing? Wouldn't it make more sense if the 571mm wheel was S-6 and the 597mm wheel size S-7? Do I care too much about this type of stuff? Yes, yes I do.