why is it that locking up the rear wheel on a coaster brake is so much easier than locking it up on a fixed gear? on a coaster brake (with similar gearing) i can lock up the wheel with ease, in sandals, seated, sipping my mocha lattechino grande... yet on my fixed gear i gotta either be clipped in and at least stand up, or i gotta put the nuts on the stem. either way it's much more difficult.

i don't know exactly what's going on in a coaster hub, but it's still backpressure on the pedals locking up the rear wheel. what's the difference? what's the coaster hub doing?