From the latter half of the 1960s to the beginning of the 1980s, in Japan, sports bicycles became the rage among children. Sports bicycles for children at that time, called junior sports bikes, actively incorporated elements of sports cars, which were admired by children. In 1971, Shimano developed a disc brake, which was the standard of sports cars, for junior sports bicycles. It attracted people’s attention as a new brake system for bicycles and enjoyed brisk sales. Although disc brakes showed less braking force decline in the rain and thus delivered stable performance, they failed to become prevalent in full-fledged sports bikes for weight and other reasons. They disappeared from the market for a while as junior sports bicycles fell into a decline. It was in the 1990s when disc brakes drew renewed attention due to their good compatibility with suspensions, which were becoming widespread in mountain bikes. They underwent subsequent improvements, and now are becoming the standard brake type for sports bikes.