Originally Posted by jimshapiro

I don't think so. Each time the back wheel makes a complete revolution all of the teeth on the cog have "done their job" once, whether there are 15, 17, or even 25 teeth (same logic holds for the chainring, with a factor for the gear ratio). It seems to me that the chain is what gets a bigger workout with larger gears. You've engaged and disengaged one revolution's worth of teeth and that could be 15, 17, or even 25 chain links. No?

Jim