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@rhowe
I don't know much about torque or tension but I think you missed a step with the above..
Surely the high RPM stops once the driveshaft or whatever it is motorbikes have meets the gearbox. The chain will only go round as fast as the wheels, which means what, at 60kph you're talking 1000 metres/min with a tyre diameter of what, about 60cm? That's about 4m circumference which means that the rear wheel's doing something of the order of 250RPM. Unless there's gearing between the rear sprocket and the wheel that's the speed the chain's going. A smaller sprocket at the front would obviously be spinning faster, let's say 4:1 which seems a bit extreme..
So that's 1000 RPM at 60kph, 2000 RPM at 120kph.
Definitely an order of magnitude faster than most people would pedal, I'd wager.