Originally Posted by icithecat

Yup. A 750cc racing motorbike generating 120hp uses alu for the rear cog (the big one) and heat treated steel for the front (the small one). These last approx 20,000 miles on a perfect chainline. I believe that a human generates 1/12th of an hp.
Don't believe for a second that skidding generates more force that whacking the throttle at 5,000 rpm.