Joined: Aug 2011
Posts: 298
Likes: 17
From: Western Massachusetts
Bikes: 2020 Kona Rove ST, 2020 Kona Woo, 2013 Cannondale Caad 10 Rival, 2020 All-City Super Professional, 2023 Kona Honzo, 1991 Bridgestone CB-1
I rode for several years with a rear rack mounted on a seatpost mount like this on an aluminum cannondale. Never had any problems commuting and carrying regularly 10-20 lbs. Sometimes more.
Eventually, after taking the rack off a few times, I wrecked the threads on the seatpost clamp.