After half-wasting another chain into metal dust, I carved a hole in the old tire with a 1/2″ drill bit. After a couple of cuts, I was able to punch through a link to the outside of the tire. Now I can either use the tire in difficult or less difficult mode.
To make the change between modes, I flip the chain around from being mounted high on the tread or low. If low, life is easier because I’m lifting up on the tire when dragging. For difficult, the tire is pulled straight if not slightly down, dramatically increasing the pulling force required to move the tire.
30 minute tire drag. I’ve also begun logging my training in an Excel worksheet, as I have yet to find a good WordPress widget to track workouts with.