Originally Posted by
msl109
I think the change in the practice is mainly about aesthetics. Yes, I suppose it could be argued that wrench flats are less aerodynamic, but I'll go out on a limb and guess that's negligible overall for 99 percent of us?
It's about weight. The extra metal for the wrench flats probably adds ~15-20g to the pedal, compared with a tapered spindle. A hex socket removes weight. And there's plenty of options, if you don't care about weight. For reference, a 105 pedal is 265g, Ultegra 248g, DA 228g. And RS500 pedals (with the wrench flats) is 320g. So Shimano could make a DA pedal with flats, but it would likely weigh as much or more than a 105 pedal.