I commute 100 + miles a week on a road bike and it works great. I wouldn't recommend going much over 30 pds for extended commuting but I find I rarely need to exceed that and I carry just about everything on the bike everyday. I used a seatpost rack and liked it, I am presently using a standard rack and like that as well.
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Sunrise saturday,
I was biking the backroads,
lost in the moment.