huh. I carry over 100 lbs of ebikes on my 1up, very likely heavier than most any mountain bikes, and they are rock stable. I have the heavy duty double version of the 1Up
Just traveling throughout Arizona and California with a 1 up rack, a heavy electric bike and a full sized mountain bike. The 1 up rack is working flawlessly. My second long range desert trip with the rack. Can’t recommend it enough!