Older 26 Inch Tire Sizes
Older bicycles built prior to the 1990's use 26" tires that are not the same size as modern 26" MTB and hybrid bike tires. These older tire size are usually labeled with a fractional width measurement, such as 26" x 1 3/8", as opposed to a 26" x 1.9".
But to make matters even more confusing, there are four different common 26" sizes that are labeled with fractional width measurements! These sizes are not interchangeable, so it's important to know which one you've got. This article should help you figure out what size you've got, but if you're at all unsure, don't guess—give us a call and we might be able to help you out, or take your wheel in to your local bike shop, and they can tell you for sure.
Your Current Tire
If you have old tires from your bicycle, there's a couple ways you might be able to figure out the size you need for your new tires.
First, look for an ISO size indication on your tire. This will take the form of a width measurement in millimeters, followed by the bead-seat diameter in millimeters. Usually this is presented in parentheses—i.e. (37-597). The important number is the bead-seat diameter (597mm in our example). If you know your bead-seat diameter, you just need to find another tire with the same measurement! You can also look on your tire for a marking matching one of the ones described below.
If it comes down to it, you can measure the beat seat diameter yourself. That's the diameter of the tire at the bead-seat-the point at which it contacts the wheel. The tire has a ridge along the edge where it contacts the wheel; that's the tire bead. Measure the diameter of the tire at this ridge, and you've got the bead seat diameter. It's important that this measurement be accurate. The difference between sizes can be just a few millimeters (as you'll see below). When in doubt, take your wheel in to a bike shop.
These tires have a bead-seat diameter of 22 1/2" (571mm). They are typically marked with S7 or S-7, and usually have marked sizes of 26" x 1 1/2" or 26" x 1 3/4". These tires were used on Schwinn middleweight bikes in the 50's, 60's, and 70's. This size is also used on some modern road bikes designed for smaller riders; in that context, the size is referred to as 650C and the width is given in millimeters. If you don't mind a narrow tire, you could conceivably use 650C road tires on your old Schwinn.
We like the Kenda K75 S-7 Schwinn 26 Inch Tire (571), though—it's inexpensive and versatile, making it a great way to get that old bike rolling again.
These tires have a bead-seat diameter of 23" (584mm) and are typically marked with 650B. This size was used on older Raleigh and Schwinn mountain bikes and French utility and touring bikes, and is currently making a comeback in a big way in the mountain bike market (modern 650B MTB tires are often labeled 27.5").
EA3 or 650A
These tires have a bead-seat diameter of 23 1/4" (590mm) and are typically marked with 650A or EA3. The most common size is 26" x 1 3/8". These tires were used on department store 3-speed bikes, children's 10-speed bikes, and some Italian road bikes designed for smaller riders.
We suggest the affordable Kenda K40 Street 26 Inch Cruiser Tire (590) or the classy gumwall Michelin World Tour 26 Inch Tire 26 x 1 3/8 (35-590) to replace old EA3 tires.
These tires have a bead-seat diameter of 23 1/2" (597mm). The most common size is, again, 26" x 1 3/8", making these tires commonly confused with EA3 tires. These tires are often, but not always, marked with S-6 or S6. They were used on older British bikes and Schwinn lightweight bikes from the 60's and 70's, and are less common than EA3 tires.
The Kenda K23 S-6 Schwinn 26" Tire 26x1 3/8x1 1/4(37-597) is a great replacement for old S-6 tires.
Any questions? Give us a call at 1-800-682-0570 or drop us a line at firstname.lastname@example.org if we can help!