Tires: 26 x 1.375 "American Lightweight" Tires (ISO 599mm)

 

 If you're you're looking for 26 x 1.375 (bead seat diameter 599mm) tires for your old, American-made utility bike, get ready to go deep into the world of vintage tires...

I say this because the tire size you are seeking is a unique one, abandoned long ago, in favor of Schwinn 26 x 1 3/8 (diameter 597mm) and British 26 x 1 3/8 (diameter 590mm). A little history is in order...

The American public has had an on-and-off relationship with bicycles over the past 120 years. In the 1890s there was a "bicycle boom", when people of all ages in the U.S. discovered the fun of riding bicycles. In the 1900s and 1910s, there was a "crash" of this bicycle boom that coincided with the rise of the affordable automobile. In the 1920s and 30s, bicycles mainly were for children and the occasional adult who needed a delivery cycle (Western Union deliverymen, for example).

A few years before WWII, several American bicycle manufacturers tried to revive adult bicycling by making lighter bicycles that were somewhat akin to British-style bikes with diamond or step-through frames and moderately wide tires. These bicycles often used a size called "26 x 1.375". The tires were made through WWII, and into the 1950s, when that tire size was gradually abandoned. By the 1960s, the size was already largely obsolete, though some tire makers may have continued making 26 x 1.375 in small numbers. 

The first thing to know is that 26 x 1.375 is not the same as 26 x 1 3/8. Yes, 3/8 may equal .375, but when it comes to tires, you can't just convert. 

So what choices do you have if you have an old, American-made bicycle that takes these tires? 

You basically have two choices, try to find good, old-stock 26 x 1.375 tires or try to adapt Kenda brand  26 x 1 3/8 Schwinn S5/S6 spec tires (bead seat diameter 597mm) to work. Using a little persistence and perhaps a little dish soap or silicone grease, you can slip the 597mm diameter tires onto many of the 26 x 1.375 (599mm) rims, then inflate carefully, making sure the tire seats properly. This will not work on all of these old rims, but on many it will work. 

The one major pitfall here is that 26 x 1.375 rims will not work with 26 x 1 3/8 British tires (590mm). The 9mm difference in the bead seat diameter is too much. That's why I say that the only real choice in a new tire is to try the 26 x 1 3/8 Schwinn S5/S6 (597mm), and see how it goes. The 2mm difference may be close enough that with some patience and fitting, you can get the Kenda Schwinn spec tire to fit the old 26 x 1.375 rim.