June 2001 The stiffness of a bike frame has a significant effect on the way a bike rides. One fact is hard to argue with: most people with a lot of cycling experience like a good stiff frame. ... While a frame is an ideal spring, your legs aren't. If you push with your legs, you use energy. ... So don't all frames flex some? ... Yes, but if you push with 10 pounds of force on a hard spring, and it moves 1 inch, you've done 10 inch-pounds of work -- loaded the spring with that much energy. ...