This vintage real photo postcard features a young man standing beside his bicycle. The look on his face can be described as similar to a “deer in the headlights”. One could also describe his expression as nervous. It is as if he just got caught doing something wrong. Maybe it has something to do with the cigarette that he is holding in his right hand, though I doubt it. He is wearing a great outfit and cap but I would surmise that his boots don’t make pedaling a bicycle particularly easy. Note that the backdrop in this studio photo is quite pretty and detailed despite that it is obviously fake. This postcard was produced in the very early 1900’s. (SOLD)
THE CABINET CARD GALLERY 
I enlarged this photo by 400%, and it seems to me that those are not boots he is wearing–I believe he is wearing some sort of leather leggings or wraps–designed to keep his trouser legs from flapping around while riding the bicycle. The leather of the leggings looks different and darker in color than that of his shoes. Just a thought, I could be wrong.
I think you are correct and that he is wearing some sort of wrap to hold his trousers in place and away from the spokes on bike tires. Great observation.