i always ride up this one hill and i'm typically forced to start from a stop due to the light at the bottom. well this one time i started sprinting up the hill and my whole drive train just locked up. turns out in one pedal i rounded the square taper part on my crank arm, sheared off the two arms inside of the freewheel on my rear wheel, sheared off 3 of the bolts that connect the two chain rings and got the chain stuck between the two rings. i'm pretty sure the crank arm was on the verge of loosening but all of the other stuff was completely functional. the wheel and freewheel were actually brand new. i showed it to my friend from a bike shop and he was amazed that all the stuff failed at one time.