If you were making a track bike and you had the torque of a 250lb track rider chromoly would be the stiffest, strongest material, but, the streets of Chicago will not humble the frame, they may humble the rims, depends on if you keep enough air in your tires. So, why not carbon fiber or titanium? What matters most, as was mentioned, is the angles of the frame, if it's stiff, it'll ride stiff, if it's soft, it'll ride soft, that's how it'll feel to the rider, the frame won't feel the bumps, the rider will, and the rider can adjust, get off the seat when a big bump is coming, as a matter of fact, jump it...