The coil spring spreads as it uncoils, putting pressure on the friction disks. This counteracts the pull of the derailer spring on the cable. The pressure required to move the lever in either is nearly equal and very light. No readjustment is necessary once they're set up correctly. Many of us consider them to be the best friction shifters ever made. Some pros insisted on using them on the Campy-equipped bikes. There is also a very rare bar end version. I have the first generation downtube version and the bar end version and I love them.