If the wheel were invented today, it absolutely would be patented. And for 20 years or whatever, the genius that solved that particular problem would reap well-deserved rewards for such a clever solution.

As far as this invention is concerned, I don't know enough about bicycling to know if this is something that's been considered and discarded before, or if literally nobody else has thought of it.

Either way, I think that makes it patentable. Either everyone else decided it wasn't worth it—and therefore nothing of value is being locked away by this patent—or they couldn't figure it out and therefore this is a novel invention for which the inventors should be rewarded for their R&D time.