Originally Posted by Chris_in_Miami

The problem with the Axiom and Blackburn is that the upper mount tab has a horizontal slot, and it's well above the mid-blade eyelets. The Jandd works without adapters because the tab has a vertical slot, so it lines up with the eyelet at some point. The vertical slot type rack won't work with u-bolt adapters, but the Tubus mid-fork adapters will work with those racks.

I was surprised to learn about this when I picked up this rack (forgot the brand) for my Schwinn, the horizontal slot is about 2 inches too high. The rack needs the adapters on two other touring bikes I've tried.