First off please say you didn't trash the old wheels! I have run across front wheels with widths less than 100mm, which is the norm as some have said, and they were older 26x1 3/8. It's hard to say if your particular bike used Schwinn's proprietary wheels that is 26x1 3/4 or possibly 26x1 3/8 also popular on English style bikes. Something bought new in a shop should be for a modern cruiser unless yours is not a modern cruiser. The older Schwinn Racer, Speedster, and Collegiate were Schwinn's 26x1 3/8 and had a narrower fork. You might call it a cruiser by looks but it might be a horse of a different color. Check the old rims for any stamping to find out if they are indeed modern or not.