I've found that pressing the little black button on the chuck relieves the pressure and then you are less likely to remove the core. However, the manual also recommends that you apply loctite to the cores...
Quick update: I cleaned the hex head, and soaked with wd-40. It still wouldn't budge and ended up stripping the head. Then I got it with an ez-out bit. Thanks for the help everyone.
I bought a set of shiny new cleats for my sidi's, but I cannot remove the old set. I bent my allen key in the process of trying to unscrew. I guess 8+ years of dirt and grime really seized up the threads. Any thoughts?
You just need to get the fit kit for your car that works with the Rack (400xt aero feet). Should be available online or at a Thule dealer. For example: http://www.orsracksdirect.com/thule-fit-kits.html