Normally I am able to determine the size of the tire needed by looking at the tire needed replacement, and I did just that. Unfortunately, 26 138 c78 does not mean 26" & 1 3/8" which is the size of the tire I bought. Should have brought my wheel. The tire was way to big for this wheel.
The bicycle is an older Giant Innova I purchased from my stepmother for my wife. I went ahead and did some measurements, but only had a standard tape and my values are a little bit off. The tire diameter is about 577mm but looking at the wheel sizes it is most likely 571mm. The inside rim width is 15.75mm and outside is 21.3mm. From what I gather at sheldons web page the correct wheel size would be either 26 x 1 or 650 C. If these tires fit the wheel size which tire should I get for the width of the rim?