Needed a replacement 700C front wheel for my commuter bike after the old aluminum rim exploded like a looney tunes cannon. It’s hard enough to find the right size when there are 3 competing tire/rim sizing systems currently in use, it doesn’t help when the people selling the wheels have no idea what the numbers mean either! All of these examples are from separate storefronts at the big online store. Ended up buying the wheel identical to mine from my local bicycle shop at the same price as online and with no shipping fee or delivery time.
The 3 systems in use are the American customary inch fraction notation like 26x1+3⁄4 (which is NOT interchangeable with American customary inch decimal notation like 26x1.75), the French metric notation like 650x45C, and the ISO 5775 metric notation like 47-571. I found the wikipedia conversion tables and Sheldon Brown’s tire size chart invaluable.
I’ve experienced this sort of thing with my car. it’s a old 50s car that had a engine swap and a few mods before I got it. so one one hand everything is universal but on the other hand I don’t know what is stock. I only know what sizes are currently under the hood. which wouldn’t be a problem if the guys at AutoZone or O’Reilly’s knew what the different sizes ment. Before I finally figured out what car my engine came from. id just measure the part I need. come in and tell them the part I need, and they would just sit confused until they just asked me what car is this part going into. sometimes the part happens to be stock bel air size, but sometimes they weren’t and the guy would have to bring the used part to the back. until they found something the right size. Hell even when I ordered online id have to wonder if I’m going to be fighting the “guarantee to fit your car thing.” because I don’t know if stock will work. Here at least you can navigate if you managed to find a conversation calculator. My measurement standards don’t matter no matter what unit I use.