I had that very same changer.
I bolted it to the garage floor and it worked just OK the first 2 tires. When it was time again I bought E3's and their tougher beads snapped the welds and twisted the upper half off. I use tire lubricant from Napa. It's slicker then my homemade concoction.
The MC adapter and upper welded tube went in the trash. Now it's just a glorified bead breaker and I use hand tire tools on everything now, including E3's and car tires. Hand tire tools do work very well as long as you take small bites. I did scratch my rim a few times in the beginning. I can now do it scratch free.
Someday I plan on one of these:
http://www.nomartirechanger.com/